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Efficacy of Popular Diets for WeightLoss and Weight Maintenance in Adults
Item Type text; Electronic Thesis
Authors Fretto, Madelynn Lea
Publisher The University of Arizona.
Rights Copyright © is held by the author. Digital access to this materialis made possible by the University Libraries, University of Arizona.Further transmission, reproduction or presentation (such aspublic display or performance) of protected items is prohibitedexcept with permission of the author.
Download date 20/02/2021 09:49:48
Link to Item http://hdl.handle.net/10150/624986
EFFICACY OF POPULAR DIETS FOR WEIGHT LOSS AND
WEIGHT MAINTENANCE IN ADULTS
By
MADELYNN LEA FRETTO
____________________
A Thesis Submitted to The Honors College
In Partial Fulfillment of the Bachelors degree
With Honors in
Physiology
THE UNIVERSITY OF ARIZONA
M A Y 2 0 1 7
Approved by: ____________________________ Dr. Claudia Stanescu Department of Physiology
TABLE OF CONTENTS I. ABSTRACT ........................................................................................................................................................... 3 II. INTRODUCTION ............................................................................................................................................... 3 III. METHODS ......................................................................................................................................................... 4 IV. RESULTS ............................................................................................................................................................ 5 IV. A. ORLISTAT ......................................................................................................................................................................... 5 IV. B. MEAL REPLACEMENT PRODUCTS ............................................................................................................................ 12 IV. C. MEDIFAST ..................................................................................................................................................................... 22 IV. D. BARIATRIC SURGERY .................................................................................................................................................. 31
V. DISCUSSION .................................................................................................................................................... 39 REFERENCES ....................................................................................................................................................... 43
I. Abstract
This review discusses popular diet methods that are advertised as effective options for
people struggling to lose weight. Obesity is a prevalent issue in the United States, which
increases a person’s risk for other comorbidities, notably cardiovascular diseases. This review
seeks to determine the most effective weight loss method by comparing Orlistat, meal
replacement products, Medifast, and bariatric surgery. The studies selected included both male
and female adults (18+ years old) classified as overweight or obese based on their body mass
index (BMI). The results showed that each of the four methods caused weight loss, but not all
sustained this weight loss. Bariatric surgery had the highest percentage weight loss for patients,
which was often sustained for many years after the procedure due to the physiological
manipulation of the digestive system. Though bariatric surgery had the most promising results,
not everyone qualifies for the procedure based on their BMI and other comorbidities. Thus, a
more feasible weight loss and maintenance plan is the Medifast program. This paid program
includes pre-made meals and the option of one-on-one counseling to implement lifestyle changes
that can be used long-term for sustained, healthy weight loss.
II. Introduction
Obesity is a serious issue that is prevalent in the United States, as well as the rest of
the world. Unfortunately, it is associated with numerous health problems and risks, including
heart disease and diabetes.7 About 64% of adults in the United States are considered overweight
or obese.7 Losing weight may seem like a relatively straightforward task, since many
recommendations include more exercise and less food intake. The weight may be seemingly easy
to lose quickly, but weight loss maintenance and avoidance of regaining this weight is the most
difficult part when it comes to dieting. There are many “quick fixes” for dieting that are
4
advertised in our everyday lives. People are constantly bombarded with the newest weight loss
products that promise the quickest and easiest ways to lose weight. It is a pressure in today’s
society to be fit and skinny. Naturally, with this type of pressure, people often look to the
quickest way to lose weight with the least amount of effort. The purpose of this literature review
is to research the efficacy of four popular diets and weight loss methods in terms of weight loss
and weight loss maintenance. These four diet methods include: 1) Orlistat, an anti-obesity
capsule; 2) meal replacement products, which include drinks or bars to substitute a solid food
meal; 3) Medifast, a paid nutrition and weight loss program; and 4) bariatric surgery, which
physically alters the digestive system. Each of these methods will be analyzed in detail and can
be compared to the others most notably by percentage of weight loss, while also including other
factors including blood pressure and cholesterol changes. The most effective diet method for
weight loss and maintenance is hypothesized to be bariatric surgery, since this surgery alters the
digestive system and can physically reduce the size of the stomach. This usually is a permanent
solution and changes the patient’s eating habits so they are not consuming as much food as they
were before.
III. Methods
The studies selected for this review included overweight and obese adults who were at
least 18 years old. Additionally, the studies included both male and female subjects. Body mass
index (BMI) is used to determine if a subject is overweight or obese. BMI is a commonly used
measurement in the medical field that divides weight (kilograms) by height squared (meters).
BMI is a simple calculation that is used for screening, and a high BMI score often correlates with
high body fat. A healthy person has a BMI of 18.5-24.9 kg/m2. In contrast, a person is considered
overweight if their BMI is 25.0-29.9 kg/m2 and obese if their BMI is 30+ kg/m2.1
5
IV. Results
IV. A. Orlistat
Orlistat, a pharmacotherapeutic drug intended for weight loss, is considered a
gastrointestinal lipase inhibitor.17 Orlistat is the only drug approved by the FDA that affects food
absorption, distribution, and metabolism.12 Orlistat hinders food digestion and fat absorption in
the GI tract by binding to lipids and impeding the functions of gastric and pancreatic lipases.12,17
Gastrointestinal lipases absorb the triglycerides found in fats people consume while eating, and
promote gastric emptying. Orlistat is a synthetic form of lipstatin, which is a lipase inhibitor that
comes from Streptomyces toxytricini bacteria.17 Orlistat functions by locally decreasing the fat
absorption that normally occurs after eating by selectively inhibiting lipase functions.12,17 By
inhibiting these lipases, lipolysis is decreased, which is hydrolysis of triglycerides, and fat
excretion via feces is increased. Additionally, lipolysis products, free fatty acids, and
monoglycerides are not absorbed as well in the body.12 The drug also decreases absorption of
cholesterol by decreasing the amount of free fatty acids. Through numerous clinical trials, results
showed there was a 30% decrease in GI fat absorption when the approved dosage of Orlistat is
taken.12,17
Orlistat is recommended for adults who are considered obese or they are considered
overweight and they have other risk factors. These risk factors can include high blood pressure,
type 2 diabetes mellitus (DM), sleep apnea, and coronary heart disease (CHD).17 Every meal
must contain fat in order for Orlistat to be effective because Orlistat specifically inhibits the
breakdown of dietary fats. A low dietary fat intake is considered less than 45 grams, so the intake
for each meal should be higher than this. A person’s diet should have less than 67 grams of fat
for 2,000 kcal daily while taking this medication.19 There are two brands of Orlistat, which are
6
Xenical and Alli, and both are approved for obesity intervention. The usual dosage for Xenical is
120 mg, three times a day, taken with a fat-containing meal or one hour after the meal. For Alli,
the dosage is 60 mg, three times a day, also taken with a fat-containing meal or one hour
afterwards.17
The National Institutes of Health (NIH) has parameters for overweight and obese patients
that must be met in order for pharmacotherapy to be considered. Adult men must have a
minimum BMI of 30 kg/m2 or a waist circumference (WC) of 40 inches. Adult women must have
a minimum BMI of 27-30 kg/m2 or a WC of 35 inches. Additionally, these patients must have
completed six months of exercise, modified diet, and behavioral changes without successful
weight loss, and they must also have two risk factors as detailed above.17
Combined results from various clinical studies have reached the conclusion that Orlistat
increases weight loss and sustains weight loss maintenance, which will be discussed below.
Figure 1 summarizes weight loss results for particular Orlistat studies.
7
Figure 1
A study by Torgerson et al. (2004) lasted four years and studied the efficacy of Orlistat.
The data showed there was more weight loss taking Orlistat for four years, compared to a
placebo. However, in order to maintain this weight loss, subjects had to continue taking the
medication, which could be considered a limitation of Orlistat. After one year, average weight
loss for the Orlistat group was 10.6 kg and after four years, average weight loss was 5.8 kg.
Another important component was that 72.8% lost at least 5% of their initial weight after one
year and 52.8% after four years. Additionally, losing weight via Orlistat decreased the risk of
developing type 2 DM by 37.3% when these subjects had decreased glucose tolerance. There
was improved regulation of blood sugar in type 2 DM subjects when Orlistat was used in
conjunction with a regulated diet. Other positive impacts of the Orlistat and diet combination
9.6%
8.3%
0
5.3% 5.6%
0
6.6%
0 0
3.7%
0
3.7%
5.1%
0 0
4.4%
0 0
5.9%
0 0
8.3%
0 0 0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
Weight Loss (kg) WC (cm) BMI (kg/m^2)
Loss (%
)
Weight Loss Results for Selected Orlistat Studies
Torgerson et al | Orlistat 120 mg | 52 Weeks
Torgerson et al | Orlistat 120 mg | 208 Weeks
Sumithran et al | Orlistat 60 mg | 24 Weeks
Douglas et al | Orlistat (Unknown Dosage) | 16 Weeks
Davidson et al | Orlistat 120 mg | 104 Weeks
Finer et al | Orlistat 120 mg | 104 Weeks
Krempf et al | Orlistat 120 mg | 72 Weeks
Rossner et al | Orlistat 120 mg | 104 Weeks
8
include: decreased total and low-density lipoprotein (LDL) cholesterol, and enhanced regulation
of glucose levels.21
The efficacy of Orlistat is improved when there is a multi-component weight loss
regimen, as this helps with weight loss maintenance. These components include: exercise,
appetite suppressants, decreasing food intake, decreasing caloric intake, and modifying eating
behaviors. There is a natural weight gain once Orlistat is no longer administered, which is why
these various components are important in limiting this weight regain.17 Clinical trials also
reached the conclusion that by combining Orlistat and a decreased caloric diet, 10% body weight
can be lost in a year, showing the importance of multi-component diets.12
Dombrowski et al. (2014) reviewed long-term weight loss maintenance interventions in
obese adults with Orlistat. These studies selected obese adults who had an average BMI of at
least 30 kg/m2 and lost a minimum 5% body weight within two years before the Orlistat
treatment. Orlistat was used for weight loss maintenance for these subjects who had previously
lost weight on their own. Five studies observed the effects of taking Orlistat at 30, 60, or 120 mg,
three times daily. The results concluded that Orlistat, in combination with lifestyle changes,
caused an average 1.80 kg weight loss after 12 months. The optimal dosage for improved weight
loss maintenance was 120 mg, three times a day, which caused an average 2.34 kg weight loss.
In contrast, taking 30 or 60 mg, three times a day, caused an average 0.70 kg weight loss. This
meta-analysis concluded that Orlistat, in combination with lifestyle and behavior changes, is
effective for weight loss maintenance. Evidence pointed to Orlistat being effective over a span of
three years when taking the optimal dose of 120 mg, three times daily. Behavioral changes,
including diet and exercise, are somewhat effective for weight loss maintenance in obese adults
for up to two years, meaning weight regain is decreased. When supplementing these changes
9
with Orlistat, there is some evidence showing that weight regain is decreased for up to three
years.6
Feigenbaum et al. (2005) evaluated the effects of Orlistat and weight loss follow-up in
three primary care offices. Primary care physicians can recommend nutritional changes,
exercises, and prescribe medication. Strictly using a diet and exercise plan is not effective in
terms of weight loss maintenance, since 95% of people regain the weight plus some within five
to seven years. Drug therapy used with a diet improves weight loss maintenance long-term.
Subjects were grouped into three treatments: A) personal diet, 120 mg Orlistat, and bimonthly
meetings with family physician and clinical dietitian; B) general diet, 120 mg Orlistat, and
monthly meetings with family physician for weigh-ins and prescription check-ups; C) low-
calorie personal diet, no medication, and monthly meetings with clinical dietitian. The daily
caloric intake was the same for the three groups: 1200 calories (women) and 1500 calories
(men). For Group A, the personal diet included foods the subject selected, while incorporating
low-fat options. The meetings included exercise recommendations and goals for diet with
positive reinforcement. The goal was to have 5% weight loss within six months and
improvement in their lipid panel. Results showed Group A had an average 5.12 kg weight
reduction, Group B had an average 7.8 kg weight reduction, and Group C had an average 3.12 kg
weight reduction. Group A had the most successful treatment had the most success in terms of
patients reaching their weight loss goal. 51% of subjects in Group A lost between five and ten
percent of their initial body weight. In all three groups, there was a decrease in triglycerides, and
Groups A and B had a significant decrease in low-density lipids (LDL), which are considered
“bad” cholesterol. In terms of high-density lipids (HDL), which are considered “good”
cholesterol, there was no change in any of the groups. The study concluded weight loss is
10
successful in a primary care office with Orlistat. The fact that Group C had the lowest weight
reduction and did not include Orlistat in the plan shows its efficacy when used in a multi-
component diet plan.7
Sumithran et al. (2014) performed an analysis of Orlistat for weight loss maintenance and
noted various health parameters, including total weight loss, blood pressure, and cholesterol.
Orlistat causes an average 3 kg weight loss, waist circumference decrease of 2.1 cm, and BMI
decrease of 1.1 kg/m2. An average of 21% more subjects lost 5% of their initial weight and 12%
more subjects lost 10% of their initial weight, compared to a placebo. In terms of maintenance,
more subjects maintained their initial 5-10% weight loss after two years of taking Orlistat 120
mg compared to a placebo. Patients given a placebo for the first year post-treatment and then
Orlistat in the second year also maintained their initial weight loss. Comparatively, patients
receiving a placebo in the second year regained an average of 30-40% of their initial weight loss.
Orlistat can also be administered after a goal weight is achieved through other methods, such as a
diet. One study described in this review included patients who lost more than 8% of their initial
weight, then were given 30, 60, or 120 mg Orlistat or a placebo for one year. After one year,
those given 120 mg had less weight regain than the placebo, with a 32% weight regain taking
Orlistat and a 56% weight regain taking the placebo. 23.5% of Orlistat patients did not regain
weight or lost additional weight compared to 16.3% in the placebo group. Orlistat decreased
systolic blood pressure (SBP) by 1.9 mmHg and diastolic blood pressure (DBP) by 1.5 mmHg in
one study. SBP was decreased by 2.46 mmHg and DBP was decreased by 1.92 mmHg in another
study. Orlistat reduced total and LDL cholesterol levels more than with diet alone. For total
cholesterol, there was an average reduction of 0.27-0.38 mmol/L and for LDL, there was an
average reduction of 0.21-0.27 mmol/L. Another included study found that receiving Orlistat 120
11
mg for six months reduced total cholesterol by 8.4% and LDL cholesterol by 10%. Orlistat
reduces LDL levels because it decreases cholesterol absorption. An additional study of
overweight adults with high cholesterol found that receiving Orlistat for six months, in
conjunction with a low-fat, low-calorie diet, decreased the levels of total cholesterol, LDL, and
triglycerides. It has been determined thus far that HDL levels are not effected by Orlistat. The
non-prescription form of Orlistat, Alli 60 mg, has about 80% efficacy, compared to the
prescription dose of 120 mg.19
Zohrabian et al. (2010) reviewed Orlistat in terms of clinical and economic
considerations. In general, weight loss from antiobesity medications is small, with values
typically from 2-10 kg. This weight loss is usually regained once the medication is stopped,
showing poor weight loss maintenance. Orlistat has the least side effects compared to other
antiobesity medications, but causes the least amount of weight loss, with an average of 3 kg.
After taking Orlistat for one year, regain of weight loss can occur even while taking the
medication. This study concludes that Orlistat is not significant for long-term health changes.
Even though it reduces diabetes risk and improves lipid panels and blood pressure values, these
are considered short-term benefits and most people do not continue taking Orlistat for long
periods of time.25
Sumithran et al. (2014) also reported some negative side effects while taking Orlistat,
even though it is considered a safe medication to take for extended periods of time. A negative
attribute of Orlistat is the possibility of an increase in appetite and desire for foods that increase
energy, which could cause weight regain. Other side effects occur in the gastrointestinal system
and include: fecal urgency, pain in the abdomen, incontinence, and fatty and oily feces due to
inhibition of lipase function. These side effects become worsened when there is an increase in fat
12
intake in the diet, which is necessary for Orlistat to be effective. These side effects have been
found to lessen as treatment continues. After one year, 91% of patients reported at least one GI
issue, but after four years, this decreased to 36%. Orlistat can also decrease the absorption of fat-
soluble vitamins. Thus, Orlistat users should supplement their treatment with fat-soluble
vitamins. Some of the particular vitamins affected include vitamin A, D, E, and beta-carotene,
but taking a multivitamin usually helps with these reductions in vitamin levels.19
IV. B. Meal Replacement Products
Meal replacement products are an alternative method for losing weight and maintaining
this weight loss, and various studies, which will be further described below, support these claims.
These quick and easy products often include pre-made shakes, drinks, powders, bars, and
entrees, and products such as SlimFast and Herbalife are popular examples. Meal replacements
substitute regular meals with low calorie products.2 Most products are calorie-reduced and meant
to replace one or two meals or snacks per day with a low fat and low energy diet.8 A study from
Basciani et al. (2015) discusses how decreased efficacy in terms of weight loss maintenance can
be attributed to lack of compliance. People want quick weight loss without much work when in
reality, programs must be followed for an extended period of time. People become disheartened
when they have significant weight loss initially, but then plateau. This is where meal replacement
products come in handy, which are composed of the necessary nutrients to decrease fat tissue
size. Weight loss maintenance is also a critical component of any diet. A study by Vázquez et al.
(2009) describes how the benefits of weight loss last only as long as the weight loss is
maintained. Many people regain the weight because of hormones, adaptive physiological
changes, and not monitoring the weight loss maintenance. Weight loss maintenance can occur if
there is a low-fat and low-energy diet, exercise, self-regulation, and professional assistance.23
13
Each kilogram lost decreases the risk of diabetes by 16%, and also decreases cardiovascular risk
factors.23 It has also been found that replacing one or two meals a day, which is called partial
meal replacement, increases subject compliance when compared to food plans.11 The following
studies will detail the benefits of using meal replacement products for weight loss and
maintenance. These benefits are evaluated in terms of total weight loss, decrease in BMI and
waist circumference, and various biomarkers, among other factors that will be further explained
below.
Studies that researched the efficacy of partial meal replacement diets looked at replacing
at least one daily meal with a meal replacement product, but still including regular healthy meals.
Partial meal replacement is a food-based strategy to decrease caloric intake. Moderately
decreasing caloric intake with a partial meal replacement diet is beneficial in decreasing body fat
and maintaining this weight loss. This treatment works slowly and progressively, which helps
with weight loss maintenance and a partial meal replacement diet is more flexible and convenient
than doing a total meal replacement diet.10 Partial meal replacements are said to be effective
because they provide reduced-calorie foods that take away the temptation to choose food that
may not be as healthy or nutritious. For the consumers, these products allow them to learn
portion control while having a normal lifestyle, and weight loss is more gradual. These products
are also easy to use and not as expensive.8 In terms of health content, meal replacement products
usually have at least 0.8 grams of protein/kg of ideal body weight each day in order to maintain
lean mass.2 Some of the meal replacement products used in these studies on overweight and
obese subjects were: Herbalife ShapeWorks, Optifast, SlimFast, Special K products, Modifast,
and Glucerna. Lee et al. (2009) accounted for the exercise regimens of the two groups for the
high protein and conventional diets and found that there was no significant difference between
14
the two. Additionally, Heymsfield et al. (2003) gave all subjects the same exercise instructions to
supplement their diet plan.
These studies concluded that partial meal replacements were effective in overall mean
weight loss. There were also decreases in BMI, waist circumference, and fat mass. A decrease in
waist circumference is significant because this has been associated with decreased cardiovascular
risks.2 Table 1 outlines the averages of weight loss results for selected partial meal replacement
studies. In terms of biomarkers, levels of blood glucose, total cholesterol, serum triglycerides,
low-density lipoprotein (LDL), and insulin were decreased and high-density lipoprotein (HDL)
levels tended to increase. Li et al. (2005) also found a decrease in triacylglycerol levels.
However, the metabolic profile showed decreased glucose levels after six months compared to
the control group, but not after 12 months. The insulin levels were not different. Two studies by
Li et al. (2005) and Vander Wal et al. (2007) found small decreases in HDL levels, which was
different from other studies. Basciani et al. (2015) found that systolic and diastolic blood
pressure decreased. However, this study found a 5.2% increase in lean body mass, which could
be attributable to the protein requirement of 0.8 grams/kilogram of goal weight in the diet plan.2
Heymsfield et al. (2003) concluded that glucose, triglyceride, and systolic blood pressure levels
were considered significantly improved with weight loss after three months, as well as
improvement in risk factors for disease. After 12 months, total cholesterol, LDL, glucose,
triglyceride, and systolic blood pressure levels were all considered significantly improved.8
Vander Wal et al. (2007) found partial meal replacements were effective in decreasing hip and
thigh circumferences, but found that for cardiovascular risks, there were no significant
differences for glucose, lipids, and other biochemical levels and the results were not considered
significant enough for cardiovascular benefits.22 Table 2 outlines the averages of biomarker
15
results for selected partial meal replacement studies. Figure 2 summarizes weight loss results for
particular partial meal replacement studies.
Vázquez et al. (2009) studied weight loss maintenance in particular, which is just as
important as initially losing weight. This study showed that a majority of the subjects maintained
their weight loss or lost additional weight in the maintenance phase. There was also a larger
decrease in absolute weight loss with the meal replacement group, however decreases in body fat
mass and fat free mass were similar for both groups. Additionally, this study found there were no
significant differences between the two groups in terms of waist circumference, fasting glucose,
lipid profiles, and blood pressure, but HDL levels increased.23
16
Table 1 Averages of weight loss results for selected partial meal replacement studies
Study Body weight
(kg)
Waist Circumference
(cm)
BMI (kg/cm2)
Truncal Fat Mass
(kg)
Whole Body Fat Mass
(kg)
Lean Body
Mass (kg) Lee et al.
High Protein Diet 3 months
-5.0 -6.3 -1.9 -1.6 -2.5 -1.1
Lee et al. Conventional Diet
3 months
-4.9 -7.1 -1.8 -1.5 -2.3 -1.7
Basciani et al. 4-Stage Program
6 months
-14.7 -12.2 -5.2 x x x
Li et al. Soy-Based MR
12 months
-4.35 x -1.44 x x x
Heymsfield et al. Liquid MR 3 months
-6.19 to
-6.50
x x x x x
Heymsfield et al. Liquid MR 12 months
-6.97 to
-7.31
x x x x x
Vander Wal et al. Cereal/nutrient bar
1 month
-3.27 -6.05 -1.18 x x x
Vander Wal et al. Cereal/waffle/nutrient bar
1 month
-2.80 -5.23 -1.08 x x x
Vander Wal et al. Cereal/no nutrient bar
1 month
-3.45 -5.93 -1.30 x x x
17
Table 2 Averages of biomarker results for selected partial meal replacement studies
Study Glucose (mg/dl)
Total Cholesterol
(mg/dl)
Triglycerides (mg/dl)
HDL (mg/dl)
LDL (mg/dl)
SBP (mmHg)
DBP (mmHg)
Lee et al. High Protein Diet
3 months
-3.8
-18.6
-70.1
+5.9
x
x
x
Lee et al. Conventional
Diet 3 months
-4.2
-11.1
-56.4
+7.6
x
x
x
Basciani et al. 4-Stage Program
6 months
-14.5
-15.2
-44.2
-0.1
x
-6.0
-6.2
Li et al. Soy-Based MR
12 months
-12.07
-10.76
x
-0.97
-6.10
x
x
Vander Wal et al. Cereal/bar 1 month
-3.6
-9.91
-3.78
-3.42
-4.86
x
x
Vander Wal et al. Cereal/waffle/bar
1 month
+1.62
-5.05
+0.36
-2.34
-2.88
x
x
Vander Wal et al. Cereal/no bar
1 month
-1.98
-9.37
-4.14
-3.60
-3.78
x
x
Figure 2
6.6%$ 6.6%$ 6.7%$6.4%$
7.4%$
6.3%$
15.4%$
12.1%$
15.4%$
4.6%$
0.0%$
4.4%$
7.3%$
0.0%$ 0.0%$
8.2%$
0.0%$ 0.0%$
3.3%$
0.0%$
3.2%$2.7%$
0.0%$
2.9%$
3.5%$
0.0%$
3.5%$
0.0%$
2.0%$
4.0%$
6.0%$
8.0%$
10.0%$
12.0%$
14.0%$
16.0%$
18.0%$
Body$weight$(kg)$ Waist$(cm)$ BMI$(kg/cm^2)$
Loss$(%
)$
Weight$Loss$Results$for$Selected$Par8al$Meal$Replacement$Studies$$
Lee$et$al$|$High$Protein$Diet$|$12$Weeks$
Lee$et$al$|$ConvenNonal$Diet$|$12$Weeks$
Basicani$et$al$|$4OStage$Program$|$24$Weeks$
Li$et$al$|$SlimFast$Soy$O$Based$MR$|$52$Weeks$
Heymsfield$et$al$|$PMR$Plan$|$12$Weeks$
Heymsfield$et$al$|$PMR$Plan$|$52$Weeks$
Vander$Wal$et$al$|$Special$K$Cereal$/$Nutrient$Bar$
|$4$Weeks$
Vander$Wal$et$al$|$Special$K$Cereal$/$Waffle$/$
Nutrient$Bar$|$4$Weeks$
Vander$Wal$et$al$|$Special$K$Cereal$/$No$Nutrient$
Bar$|$4$Weeks$
18
The specific studies that concluded similar findings had their own variations of partial
meal replacement diets. Lee et al. (2009) researched the efficacy of a low-calorie and partial
meal replacement diet in obese subjects that had metabolic syndrome. The purpose of this study
was to research the effectiveness of high-protein versus conventional diets that both have partial
meal replacements. The meal replacement plan required that the subjects consume the meal
replacement products two times a day and a normal meal once a day. Overall, the high-protein
diet decreased body fat more than the conventional plan. This study suggests that a high-protein
diet with partial meal replacement could be useful for decreasing weight and abdominal in obese
subjects diagnosed with metabolic syndrome.10
Basciani et al. (2015) also researched a low-calorie and partial meal replacement diet by
evaluating a four-stage program that used meal replacement products and a very low calorie diet
(VLCD) at the start, while slowly adding more food into the diet to ultimately end up at a
hypocaloric balanced diet (HBD). The subjects slowly transitioned from four or five meal
replacement protein products in the first stage to a HBD with one meal replacement in the last
stage. The results showed a range of weight loss between 8.0 and 35.7 kg. Each month, there was
an average weight loss of 2.45 kg and overall, there was an average weight loss of 15.4%. This
program is unique because it included stages that slowly moved from a very low calorie diet to a
HBD. It was concluded that this multi-step program is a safe way to treat obesity and guide
people to a healthier lifestyle. Weight loss maintenance was best when transitioning from a
VLCD and slowly adding carbohydrates to a healthy level.2
Li et al. (2005) studied the effects of a soy-based meal replacement in obese subjects
diagnosed with type 2 diabetes. This plan progressed from three meal replacement shakes per
day, to two meal replacements and a regular meal, and lastly one or two meal replacements and
19
one or two regular meals. The mean weight loss was 2.28% higher than the control group. The
study concluded that between the meal replacement and control groups, the levels for total
cholesterol, triacylglycerol, HDL, and LDL were not considered significantly different. A
significantly positive benefit of the meal replacement treatment was that many of the subjects
decreased their intake of metformin and sulfonylurea, which are medications used to manage
type 2 diabetes. Overall, this study concluded there was significant weight loss with a soy-based
meal replacement for type 2 diabetics.11
Heymsfield et al. (2003) published a meta and pooling analysis of weight management
with partial meal replacement, which was the first study until that point to perform an assessment
of the efficacy and safety of meal replacements. The study describes a partial meal replacement
plan as a low calorie diet containing one or two meal replacements with reduced calorie snacks
and meals. The subjects used liquid meal replacements twice a day in the weight loss phase and
one replacement a day in the maintenance phase. After three months, weight loss for the meal
replacement group was found to be an average 7% loss. After 12 months, weight loss was found
to be an average 7-8% loss. An important result was that after three months, 72% of meal
replacement subjects lost at least 5% of their initial body weight, and after 12 months, 74% lost
this amount of weight. The study concluded that a partial meal replacement plan causes more
weight loss and maintenance when compared to a control group, in this case a reduced calorie
diet. The average amount of weight loss for these subjects after 12 months is considered enough
to lower risk of disease. An interesting component was that the researchers compared diabetic to
non-diabetic subjects after 12 months and found that diabetics’ weight loss maintenance was
lower than nondiabetic subjects, which can be attributed to their use of insulin.8
Vander Wal et al. (2007) researched cereal partial meal replacements and the effects on
20
weight loss, cardiovascular risks, and compliance. This study describes how low and moderate
carbohydrate diets are most effective in decreasing weight, fat, and waist/hip/thigh
circumferences. There were three types of meal replacement groups: cereal plus nutrient bar for a
snack, cereal and a waffle plus nutrient bar, and cereal with no nutrient bar. These groups were
able to choose a third meal of their own, so they had two replacement meals per day. The results
found that adherence to the three diets was high and all three had significant decreases in weight,
BMI, and hip, waist, and thigh circumferences, and body fat percentage for the cereal/nutrient
bar and cereal/no nutrient bar groups. For the cardiovascular risks, there were no significant
differences between the three groups for glucose, lipids, and other biochemical levels and the
results were not considered significant enough for cardiovascular benefits. There were also no
significant differences between the groups for urges to overeat, thinking about food more than
normal, craving food/hunger, and guilt for submitting to cravings, among other emotional
factors. This study concluded that adherence was better for the cereal/nutrient bar and cereal/no
nutrient bar plans, which could be explained by the fact that they required fewer products to
implement daily. Also, these products are helpful for short-term weight loss, since this was not a
long-term study and accounted for four-week changes.22
Vázquez et al. (2009) researched the efficacy of a meal replacement with a low caloric
intake formula that replaced dinner in regard to weight loss maintenance. This study gives a
guideline of how meal replacement products can be used to maintain weight loss after losing the
weight initially by dieting. The results showed that in the meal replacement group compared to a
control group, 83.9%, or 26 of the 31 subjects, maintained their weight loss or lost additional
weight and decreased their initial weight from the start of the maintenance phase by 3.2 kg.
There was also a larger decrease in absolute weight loss with the meal replacement group, which
21
was 3.1 kg. It was concluded that using a meal replacement that is low-calorie is better for
weight loss maintenance when contrasted with dieting. The subjects had better weight loss
maintenance and lost over two times the weight without losing more lean body mass. The study
concedes that maintenance is difficult, but the benefits of using meal replacement formulas are
considered safe, easy to follow, and cost less than pharmaceutical drugs, with similar results.
There is also evidence that meal replacement products can be used to initially begin the weight
loss phase, while also maintaining it afterwards. The researchers believe that enhanced weight
loss maintenance and increased weight loss in the maintenance phase can occur if there is a more
gradual drop in weight during the induction stage.23
Ross et al. (2016) published a review article researching very low energy meal
replacements for weight loss in obese subjects who are about to undergo surgery. Even though
this study is focused on a group of people that are having surgery, it gives beneficial information
on meal replacements targeting weight loss since it studied short-term weight loss for an average
of four weeks. This very low energy diet contained decreased fat and carbohydrates and high
protein to maintain lean body mass while decreasing fat. In terms of percentage of total weight
loss, ten studies found subjects lost more than 5% of their starting weight, which as stated before,
causes various health benefits and decreases risk factors. Seven studies found subjects lost more
than 10% of their starting weight. Six studies also measured fatty liver size and its reductions
throughout the process and found liver reductions greater than 10%. Liver reduction is helped
when there is a change in diet and decreases in weight and BMI. There were also decreases in
total fat mass and thickness of adipose and visceral tissue. In follow-up measurements, it was
found that risk factors such as levels of insulin, glucose, and lipids were all improved. This study
shows that meal replacement plans are relatively easy to adhere to and can be used in clinical
22
settings for interventions.15
An important component of any diet is how satisfied and “full” the consumer feels after
eating, which helps prevent overeating. Tieken et al. (2007) researched whether solid or liquid
meal replacements are more effective in regulating hunger and feeling full by affecting appetite-
regulating hormones. These appetite-regulating hormones include leptin, insulin, ghrelin, and
cholecystokinin (CCK), which regulate eating and body weight. When the subjects consumed the
solid and liquid products, it was found that after one hour, hunger in the solid group increased
less than the liquid group. After four hours, hunger in the solid group was 45% lower than
fasting level, but hunger in the liquid group was 14% higher than fasting level. The desire to eat,
over the span of four hours, was lower for the solid group compared to the liquid group. Blood
glucose levels increased significantly after 15 minutes with the liquid meal replacement, but took
60 minutes to increase significantly for the solid meal replacement. Insulin levels were lower
after 15 and 120 minutes for the solid group. Ghrelin levels were also lower in the solid group
and were lower than baseline levels up to four hours after eating. Leptin and CCK levels were
similar between the solid and liquid groups and hardly changed over the four-hour post-meal
period, however. Overall, it was concluded that solid meal replacements, such as a nutrient bar,
cause decreased hunger and desire to eat after consumption and are not equivalent to liquid meal
replacements for weight loss. These results are important because this can help people increase
and maintain their weight loss since it is easier to comply with a diet that makes you feel more
full and satisfied.20
IV. C. Medifast
The Medifast program is a paid weight loss and maintenance regime that works with
clients to reach their goals. Medifast is a type of meal replacement plan that has meals pre-made
23
for clients that are proper portion sizes so they do not have to worry about cooking their meals
properly.18 There are two approaches for clients, which includes either following the program on
their own or going to Medifast Weight Control Centers. If a person chooses to follow the plan on
their own, they can find the right plan for them on the Medifast website. The options are either
the Flex Plan for gradual weight loss or the Go! Plan for rapid weight loss. The Flex Plan has
four Medifast meals, two Lean & Green meals (lean protein and vegetables), and one healthy
snack, making it the 4 & 2 & 1 Plan. The Go! Plan has five Medifast meals and one Lean &
Green meal, making it the 5 & 1 Plan. Once the client decides the plan that works for them, they
can order the meals online, which are then shipped to their home. There are options where clients
can order 30 days of meals or individual products. The other approach for clients at the Medifast
Weight Control Centers is more personalized and includes a body composition analysis and face-
to-face counseling.13 Medifast Weight Control Centers supervise clients to ensure they are
meeting their weight loss goals by having scheduled visits, ensuring they are following their
meal replacement plans, and encouraging them to keep a food/exercise diary. Medifast combines
Medifast meals and traditional food for a balanced diet plan. The Medifast program gathers
information about the client’s health before determining a suitable plan, including a health
review with their past medical history and blood work. Each client meets weekly with their
counselor, and the weekly sessions are comprised of: weigh-ins, blood pressure evaluation,
ketone testing, looking at their food diary, behavioral and lifestyle changes, and choosing meals
for the following week. Clients also have the option of measuring their body fat mass, lean
muscle mass, and percent body fat every four weeks, at an additional cost. The weight loss phase
length depends on each client, so no two plans are alike.3 The meal plans are customized to each
client’s individual needs and are based on the lifestyle of the client, their preferences, and past
24
medical history. The client and counselor determine the weight loss goal, and then an
individualized weight loss phase and weight management program is created.4
The Medifast three-step approach is: active weight loss, transition, and maintenance. The
active weight loss phase uses one of the Medifast plans, such as the 5 & 1 Plan described above.
The transition phase has the clients slowly decrease the number of Medifast meals and add
traditional food that gives them their energy needs to maintain their weight loss. The length of
the transition phase depends on how much weight was lost: 50 pounds is an eight week phase,
51-100 pounds is a 12 week phase, and greater than 100 pounds is a 16 week phase. The
maintenance phase lasts 52 weeks and includes a set meal plan with Medifast meals and
traditional foods. This meal plan is also individualized and is determined by the energy needs
necessary for long-term weight loss maintenance.3
The studies below included overweight and obese subjects and concluded that the
Medifast program is effective for not only weight loss, but also maintenance. An additional
benefit of this program is the improvement of various biomarkers that decrease the risk for
various diseases, particularly cardiovascular disease. Table 3 summarizes the averages of weight
loss results and Table 4 summarizes the averages of the biomarker results. Figure 3 summarizes
weight loss results for particular Medifast studies.
25
Table 3 Averages of weight loss results for Medifast studies Study Body
Weight (kg)
Waist Circumference
(cm)
BMI (kg/cm2)
Fat Mass (kg)
Fat-free Mass (kg)
Lean Muscle Mass (kg)
Shikany et al. 5 & 1 Plan Weight loss (26 weeks)
-7.5
-5.7
-2.6
-6.4
-1.2
x
Shikany et al. 5 & 1 Plan
Maintenance (52 weeks)
-4.7
-5.0
-1.6
-4.1
-0.6
x
Davis et al. 5 & 1 Plan Weight loss (16 weeks)
-13.5
-13.0
-4.7
x
x
-1.8
Davis et al. 5 & 1 Plan
Maintenance (40 weeks)
-8.9
-9.7
-2.9
x
x
-1.8
Coleman et al. 4 & 2 & 1 Plan
12 weeks
-10.9
-9.8
-3.7
x
x
x
Coleman et al. 4 & 2 & 1 Plan
24 weeks
-16.0
-13.6
-5.5
-14.5
x
-3.1 Coleman et al.
5 & 1 Plan 4 weeks
-5.8
-4.1
x
-4.6
x
-1.9
Coleman et al. 5 & 1 Plan 12 weeks
-11.9
-10.2
x
-9.2
x
-2.0
Coleman et al. 5 & 1 Plan 24 weeks
-17.3
-15.2
x
-14.3
x
-2.8
26
Table 4 Averages of biomarker results for Medifast studies Study SBP
(mmHg) DBP
(mmHg) Total
Cholesterol (mg/dl)
Triglycerides (mg/dl)
HDL (mg/dl)
LDL (mg/dl)`
HR/Pulse (bpm)
Glucose (mg/dl)
Shikany et al. 5 & 1 Plan Weight loss (26 weeks)
-3.2
-1.6
-8.4
-3.7
+1.2
-9.2
x
-1.1
Shikany et al. 5 & 1 Plan
Maintenance (52 weeks)
-0.5
+0.6
-0.3
-7.5
+2.1
-1.3
x
-2.2
Davis et al. 5 & 1 Plan Weight loss (16 weeks)
-10.9
-6.5
-9.9
-17.4
-0.4
-5.9
-9.2
x
Davis et al. 5 & 1 Plan
Maintenance (40 weeks)
-6.0
-5.5
-9.2
-1.5
+1.2
-10.2
-6.6
x
Coleman et al. 4 & 2 & 1 Plan
12 weeks
-11.3
-6.6
x
x
x
x
-3.0
x
Coleman et al. 4 & 2 & 1 Plan
24 weeks
x
x
x
x
x
x
-3.7
x
Coleman et al. 5 & 1 Plan
4 weeks
-8.0
-5.3
x
x
x
x
-2.8
x
Coleman et al. 5 & 1 Plan 12 weeks
-8.6
-6.4
x
x
x
x
-4.1
x
Coleman et al. 5 & 1 Plan 24 weeks
-15.6
-9.2
x
x
x
x
-3.7
x
27
Figure 3
The specific studies researched the Medifast program, but with their own approaches.
Shikany et al. (2013) researched the Medifast 5 & 1 Plan, which includes portion-controlled, low
fat, and nutritional meals. This study compared the Medifast diet to a reduced-energy diet with
meals selected by the subject based on healthy food lists. The Medifast 5 & 1 Plan is available
for purchase and the program setup is five meals and a meal the client chooses with lean protein
and three vegetable servings every day. The Medifast group during the weight loss phase was
provided five low-fat meals and the choice of one “Lean & Green” meal, which was lean protein
and vegetables. The subjects had the choice between 70 meals for their five meals a day and
consumed 800-1000 kilocalories daily. The “Lean & Green” meal consisted of five to seven
ounces of lean meat or other protein, 0-2 servings of healthy fat, and three 0.5-1.0 cup servings
of vegetables that were low in carbohydrates. Subjects also become part of an online community,
where they could talk with trainers and dietitians and chat with other people in the program.
Recipes were also provided. For both groups during the weight loss maintenance phase, the
subjects’ energy needs were calculated to maintain their weight while also factoring in their daily
6.7%%
5.3%%
6.4%%
4.2%%4.6%%
4.0%%
12.1%%
11.1%%
12.2%%
8.0%%8.3%%
7.5%%
10.0%%
0.0%%
9.9%%
14.7%%
0.0%%
14.7%%
6.0%%5.5%%
0.0%%
12.1%%
8.5%%
0.0%%
17.0%%
12.4%%
0.0%%
0.0%%
2.0%%
4.0%%
6.0%%
8.0%%
10.0%%
12.0%%
14.0%%
16.0%%
18.0%%
Body%Weight%(kg)% Waist%Circumference%(cm)% BMI%(kg/m^2)%
Loss$(%
)$
Weight$Loss$Results$for$Selected$Medifast$Studies$$
Shikany%et%al.%|%5%&%1%Plan%|%Weight%Loss%|%26%weeks%
Shikany%et%al.%|%5%&%1%Plan%|%Maintenance%|%52%weeks%
Davis%et%al.%|%5%&%1%Plan%|%Weight%Loss%|%16%weeks%
Davis%et%al.%|%5%&%1%Plan%|%Maintenance%|%40%weeks%
Coleman%et%al.%|%4%&%2%&%1%Plan%|%12%weeks%
Coleman%et%al.%|%4%&%2%&%1%Plan%|%24%weeks%
Coleman%et%al.%|%5%&%1%Plan%|%4%weeks%
Coleman%et%al.%|%5%&%1%Plan%|%12%weeks%
Coleman%et%al.%|%5%&%1%Plan%|%24%weeks%
28
total energy expenditure. For the Medifast subjects, they were able to have 0-3 meals for their
individual calculated energy needs, and the other group made their own meals. Overall, the
Medifast group decreased their weight, BMI, waist circumference, and fat mass from the starting
weight. This study concluded that Medifast yielded better results for weight, BMI, waist
circumference, and fat mass after 26 weeks compared to the reduced-energy diet, which was the
weight loss phase. The Medifast plan also maintained their weight, BMI, and fat mass after 52
weeks, which was the maintenance phase. Compared to the other diet, decreases in cholesterol
and LDL were greater in the Medifast group after 26 weeks. At the 52-week mark, there were
greater decreases in weight, BMI and fat mass in the Medifast group. The authors discussed how
portion control helps with weight loss because people do not have to make the portion sizes on
their own, with the possibility of making them too large. A plan that is set and organized makes
it easier to follow, and in this study, more people finished the Medifast diet compared to the
other diet. The strength of this study is that the Medifast plan incorporates real food, which the
authors think is a more realistic way to lose weight and incorporate into a regular diet plan.18
Davis et al. (2010) compared two hypocaloric diets: Medifast 5 & 1 Plan and an
isocaloric food diet, and both were comprised of 1000 kilocalories daily. The maintenance phase
included a slow increase of calories so the subjects’ energy levels could be maintained with three
to five Medifast meals. The results showed that in the weight loss phase, 92.9% of Medifast
subjects lost at least 5% of their initial body weight, whereas 55% of the isocaloric diet subjects
did so. Additionally, 75% of Medifast subjects lost at least 10% of their initial body weight,
whereas 25% of the isocaloric diet subjects did so. For the maintenance phase, 61.5% of
Medifast subjects maintained at least 5% weight loss and 30% of the isocaloric diet subjects did
so. Additionally, 38.5% of Medifast subjects maintained at least 10% of their weight loss and
29
20% of isocaloric diet subjects did so. There were significant improvements only in the Medifast
group for DBP and waist circumference after 40 weeks. Decreases in central obesity and waist
circumference also decrease the risks for coronary heart disease and mortality, among other risk
factors. The study concluded that the Medifast diet had twice the weight loss compared to other
diet during the 16-week weight loss period. Even though the Medifast group had more weight
regain during the maintenance period, the Medifast group was better at maintaining clinically
significant weight loss (which is 5% of initial weight within a year). The Medifast group lost
more body fat and visceral fat and maintained their lean muscle mass. Maintaining lean muscle
mass is important for overall weight loss maintenance. The low fat, low carbohydrate, and high
protein diet of Medifast can account for this lean muscle mass maintenance.5 Lean mass helps
with the strength and physicality of subjects, and with their basal metabolic rate, which plays a
role in weight loss maintenance. It is suggested that 1.1-1.6 g/kg of body weight is consumed as
protein to maintain lean mass while losing body weight. The Medifast plan allows subjects to
consume adequate amounts of protein.4
Coleman et al. (2015) was a retrospective chart review study that evaluated the
effectiveness of Medifast in an actual setting, instead of a controlled study. The meal plan in this
study is the Medifast 4 & 2 & 1 Plan, which is greater in caloric intake compared to the typically
used Medifast 5 & 1 Plan. This higher-calorie plan can be used for clients who exercise
frequently or wish to consume dairy, grains, and fruit every day, which is usually not allowed in
other types of weight loss programs. The Medifast 4 & 2 & 1 Plan is 1,100-1,300 kilocalories per
day. The plan includes: four Medifast meals, two lean protein and vegetable meals, and one
snack, which can consist of grains, dairy, or fruit. The Medifast meals are comprised of 11-15
grams of protein, 8-15 grams of carbohydrates, and 0-3.5 grams of fat. The program has an
30
optional transition phase where the amount of calories and traditional food is slowly increased to
mimic daily choices the clients will have to make. The maintenance phase is comprised of three
Medifast meals and three traditional meals the client makes, and the specific plan is formatted
based on their total energy expenditure. Weight loss was considered significant after 24 weeks,
and the highest amount of weight loss occurred within the first two weeks of starting the
Medifast program. After 12 weeks, 85% of clients had decreased their initial weight by a
minimum 5%, and 50% of clients had decreased their initial body weight by at least 10%. After
24 weeks, 96% of clients had decreased their initial weight by at least 5% and 75% of clients had
decreased their initial weight by a minimum 10%. After four months, 50.2% of the clients who
completed the program lost a minimum 5% of their initial body weight. The first four weeks
showed decreases for SBP, DBP, and HR, which decrease the risk for cardiovascular disease.
This study was unique because it analyzed the differences in weight loss between males and
females. Males decreased their weight by 1.4 kg more than females over the span of 12 weeks.
Males decreased their body fat mass by 36.8% and females by 26.4%, and males lost more fat
mass than females. There were 14% of clients who went into the transition phase and lost an
additional 0.5 kg. Additionally, there were 20% of clients who went into the maintenance phase,
averaging 34 weeks long, and the average weight regain was 1.6 kg. At the end of the
maintenance phase, the average weight loss was 16.8 kg, which was 15-16% loss from the initial
starting weight. The clients who went through the Medifast maintenance phase decreased their
weight by 16.2 kg, whereas those who did not decreased their weight by 9.2 kg. Regardless of
the length of their individual plan, 70% of the clients decreased their weight by at least 5%. The
clients averaged one year on this Medifast program, and the average weight loss maintained was
17 kg, which concludes that Medifast is effective in terms of weight loss maintenance.4
31
Coleman et al. (2012) also researched the Medifast 5 & 1 Plan. The average amount of
time for the weight loss phase was 19.6 weeks, the average time for transition was 7.9 weeks,
and the average time for maintenance was 16.3 weeks. The results showed that during the
transition phase, the average regain was 0.45 kg, but weight loss was still maintained from initial
weight, which was 15.4 kg. During the maintenance phase, the average regain was 1.9 kg, but
weight loss was still maintained from initial weight, which was 14.3 kg. The study found that
there was clinically significant weight loss of at least 5% with every client. At 24 weeks, the
average weight loss was 17.2 kg and clients maintained 97.5% of the weight they lost after the
maintenance phase. Medifast emphasizes body fat loss, and after 24 weeks, there was 8.5% loss
of body fat and 14.3 kg lost in fat tissue. The study concluded that Medifast is effective because
it keeps clients accountable with weekly individual sessions. It was found that clients who were
diligent with their weekly meetings lost more weight after six months compared to those who
were not as diligent.3
IV. D. Bariatric Surgery
Bariatric surgery has become an increasingly popular method for weight loss and its
efficacy is supported by results of clinically significant weight loss. There are about 344,000
bariatric surgeries each year around the world and there has been a significant increase in
laparoscopic bariatric surgeries over the years.17 The history of this surgery began in the 1950s
when it was known that people with a gastrectomy or short bowel syndrome had weight loss
because parts of their intestines were removed.9 Nowadays, this surgery alters the gastrointestinal
organs so body weight is lost through metabolic and physiological ways. Bariatric surgery is
effective through one of two methods: 1) decreasing consumption of food due to decreased
stomach size or 2) decreasing the absorption surface of the digestive tract, causing
32
malabsorption. These surgeries decrease the feeling of hunger, alter food choices, enhance the
feeling of satiation when eating to prevent overeating, and altering energy use. There are various
types of bariatric surgery, which include gastric bypass, vertical sleeve gastrectomy, and
adjustable gastric banding.14
Bariatric surgery tends to be an option for people who have been unable to lose a
significant amount of weight by other means, such as diet, exercise, and pharmacotherapy. The
criteria for bariatric surgery are a BMI greater than 40 kg/m2 or a BMI of 35-40 kg/m2 and other
comorbid diseases, as well as ineffectual medical therapy. Recently, there has been approval for
people with BMI of 30-35 kg/m2 and type 2 diabetes. Additionally, if people are undergoing
bariatric surgery, they are counseled on obesity and that they must decrease their energy intake
after surgery. Their surgical risk is determined, such as if they have cardiovascular and
pulmonary diseases. If a patient had cardiovascular disease, it may be considered too high of a
risk to perform surgery. Assessment of the psychological state of patients can identify whether
they have depression, binge eating disorder, and other diseases that could impact the success of
the surgery.24
Some of the more common types of bariatric surgery will be described below. One type
of bariatric surgery is Roux-en-Y gastric bypass (RYGB). In this procedure, the stomach is
separated into two parts: the upper stomach pouch and lower, gastric remnant. The stomach
pouch is connected to the mid-jejunum via an anastomosis and the bowel continuity is restored.
The lower gastric remnant is closed off from food exposure. Another type of surgery is
adjustable gastric banding (AGB), where an adjustable plastic, silicone ring is placed around the
proximal part of the stomach, making a pouch. A third common procedure is the biliopancreatic
diversion, which includes a partial gastrectomy with a gastric pouch. The small bowel is also
33
divided and a gastroenterostomy is made. One of the more popular procedures is the vertical
sleeve gastrectomy (VSG), which removes part of the lateral stomach and includes a
biliopancreatic diversion.14 Bariatric surgery has shifted to a more laparoscopic approach for
many of the procedures, which makes the surgery as minimally invasive as possible.24 The
mortality rate post-surgery has been reduced to 0.3%, making it a reasonably safe surgery,
despite the dramatic changes to the gastrointestinal system.14
Studies show that RYGB, AGB, and VSG bariatric surgical techniques can cause 20-35%
of total body weight loss, as well as weight loss maintenance. There are numerous health benefits
that are associated with this weight loss, including improvement in cardiovascular, respiratory,
renal, metabolic, and musculoskeletal diseases, and a decrease in mortality rates.14 Figure 4
summarizes weight loss results for particular bariatric surgery studies.
34
Figure 4
Miras et al. (2013) published a review on various types of bariatric surgery and their
effectiveness in not only weight loss, but also weight loss maintenance. This review discussed
how low-calorie diets are effective in the weight loss phase, but weight loss maintenance is
difficult because of behavioral patterns such as increased hunger and desire for food high in fats
and sugar. On the other hand, bariatric surgery has been found to change these behavioral
patterns so weight loss maintenance is achievable. Bariatric surgery allows people to decrease
hunger and increases satiation while eating so they feel full faster and do not overeat. In terms of
the food preferences of people who have undergone bariatric surgery, it has been found that
RYGB surgery causes patients to choose low-fat and low-sugar foods. An explanation for this
phenomenon includes avoidance and learning via physiological processes. Food preferences after
this type of surgery are affected by Dumping Syndrome, which causes abdominal pain and
nausea when a person consumes high-carbohydrate and high-fat foods. In terms of energy
16.10%&
42.60%&
50.30%&
55.20%&
77.50%&
55%&53.30%&
59.30%&63.20%& 63%&
70%&
84%&
79%&
13%&
25%&
16%&
44.30%&
61.10%&
12%&
45%&
15.90%&
0.00%&
10.00%&
20.00%&
30.00%&
40.00%&
50.00%&
60.00%&
70.00%&
80.00%&
90.00%&
Loss$(%)$
(1)$=$Ionut$et$al$(2)$=$Shah$et$al$$$(3)$=$Wolfe$et$al$
Weight$Loss$Results$for$Selected$Baria>c$Surgery$Studies$
(1)&10&year&avg.&&
(1)&LABG&&1&year&
(1)&LABG&&&2&years&&
(1)&LABG&&3&years+&
(1)&SG&&3&years&&
(1)&SG&&5&years&&
(1)&SG&&6&years&&
(1)&RYGB&&<2&years&
(1)&RYGB&>2&years&&
(1)&RYGB&&3&years&&
(1)&BPD&&Average&&
(1)&BPD&&3&years&&
(1)&Gastric&banding&&1&year&&
(1)&Gastric&banding&&10&years&&
(1)&Gastric&bypass&&10&years&&
(1)&VBG&&10&years&&
(2)&LSG&&1&year&&
(2)&LRYGB&&1&year&&Weight$Loss$(kg)$
35
expenditure after bariatric surgery, it has been found that resting energy expenditure is stable or
decreased.14
Ionut et al. (2013) discussed how bariatric surgery has the highest efficacy for treating
obesity. After ten years, the amount of weight loss was 16.1%, which is significant. A few of the
procedures discussed include laparoscopic adjustable gastric banding (LABG), which is the most
common procedure. A silicone band is put around the stomach, which decreases the gastric size
and creates a pouch that is 15 ml in size. The size of the silicone band can be adjusted as
necessary, so the band can be tightened to increase weight loss. LAGB increases weight loss by
restricting the amount of food the person will ingest because of the reduction in gastric size.
Results show that the average weight loss is 42.6% after one year, 50.3% after two years, and
55.2% greater than three years. Additionally, there was an average weight loss of 27 kg less than
two years after surgery, and 38 kg greater than two years after surgery for LAGB. A sleeve
gastrectomy (SG) involves a left partial gastrectomy that makes the stomach a tubular shape,
with the size and shape resembling a banana. This physical change causes increased gastric
emptying, which means there is faster deposition of nutrients into the small intestine. The
average weight loss is 77.5% after three years and 53.3% after six years.9
The most common gastric bypass (GB) procedure is Roux-en-Y-gastric bypass (RYGB),
which is performed laparoscopically. This procedure decreases the gastric volume with a gastric
pouch that is 15-30 ml in size. The flow of nutrients is switched from the stomach to the
proximal jejunum, via an anastomosis. This causes a decrease in stomach size, faster gastric
emptying, as well as neural and hormonal differences. The average weight loss is 59.3% (45.3
kg) less than two years after surgery and 63.2% (41.4 kg) greater than two years after surgery.
The biliopancreatic diversion (BPD) procedure involves a gastrectomy and enteroenterostomy.
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This creates a bypass of the duodenum and entry for pancreatic and biliary secretions, which
causes slower food mixing with biliopancreatic secretions. Weight loss for this procedure is
70.0%, which is typically maintained long-term. Less than two years after surgery, there is
weight loss of 38.0 kg and greater than two years after surgery, weight loss averages 49.8 kg.
However, this procedure is used only 2% of the time around the world because there is evidence
of deficiencies in nutrients for patients. Comparatively, LAGB is the most common procedure,
indicating its safety and efficacy.9
Malabsorption is considered one way that such significant weight loss is achieved. Some
of these procedures, such as BPD and RYGB, bypass a large part of the small intestine so there is
no contact with the nutrients from ingested food. Another reason proposed for this dramatic
weight loss is a decrease in caloric intake after surgery, which is decreased to a very low amount,
typically 200-300 kcal daily. However, this is only immediately after surgery and is the cause for
weight loss initially. More long-term effects include a decrease in the length of time needed to
lose weight after bariatric surgery, compared to a low calorie diet. For example, people with
gastric bypass surgery lost 10 kg in 30 days, compared to 55 days for people on a low calorie
diet.9
Ionut et al. (2013) discusses the success of initial weight loss after bariatric surgery, but
the long-term weight loss maintenance efficacy was questioned. After ten years, the average
weight loss was 16%, specifically 25% in gastric bypass, 16% in VBG, and 13% in gastric
banding groups. It was found that 20% of people regained the weight after one to three years.
With gastric banding, there was 79% weight loss after one year, but BMI gradually increased by
0.42 kg/ m2 each year. With RYGB surgery, 56% of people regained their weight lost, and after
five years, weight regain was 84.8%. However, after three years, the weight loss was 63% for the
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RYGB group and 84% for the BPD group, specifically the duodenal switch surgery. Weight loss
success measures weight loss as greater than 50%, which was accomplished by 83% of people in
the RYGB group and 98% in the BPD duodenal switch group. For the SG procedure, there was a
55% weight loss after five years, while 19% of people regained at least 10 kg. There is no
specific reason for weight regain post-surgery, but some of the mechanisms proposed include
Peptide YY (PYY), leptin, and ghrelin. In rat models that had RYGB performed, weight loss was
not sustained in the rats that had low PYY to leptin concentration ratios. It was found in another
study that the amount of ghrelin was higher in patients who could not maintain their weight loss.9
Shah et al. (2016) compared weight loss in morbidly obese subjects after laparoscopic
vertical sleeve gastrectomy (LSG), which has become the more common procedure, compared to
laparoscopic Roux-en-Y gastric bypass (LRYGB). One of the reasons for this shift in popularity
of LSG is the American Society for Metabolic and Bariatric Surgery stated that sleeve
gastrectomy is now classified as a primary bariatric surgery. Additionally, there are fewer
complications after LSG than LRYGB. This study compared postoperative factors between the
groups after ninety days and found that the hospital stay length, admission to ICU, and
complications were similar for both procedures. However, the LRYGB group had more frequent
visits to the emergency department in this ninety-day period. After one year, the estimated body
weight loss for the LSG group was 44.3%, compared to 61.1% in the LRYGB group. Overall,
LRYGB was found to have greater weight loss one year after surgery, and other factors,
including a lower BMI and a lack of type 2 diabetes, also increased weight loss in this one-year
period. Type 2 diabetes can impact weight loss, and the possible mechanism for this is that the
medications people take for diabetes increase insulin in the blood, which causes lipogenesis.
These two procedures had similar rates of mortality and morbidity, however patients undergoing
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LSG had a lower risk of being hospitalized or going to the emergency department after surgery.
This study discussed how other studies found similar weight loss results comparing LSG and
LRYGB.16
Wolfe et al. (2016) researched the efficacy of bariatric surgery on not only weight loss,
but also other diseases caused by obesity. Weight loss is correlated with decreased risk of
comorbidities and a better chance of living a longer, healthier life. People with respiratory
failure, congestive heart failure, and difficulty moving around can improve these issues with
dramatic weight loss via bariatric surgery. Some comorbidities caused by obesity include:
cardiovascular, metabolic, pulmonary, musculoskeletal, and numerous other diseases that are
aimed to be improved with surgery. This study discusses the RYGB, sleeve gastrectomy,
biliopancreatic diversion, and adjustable gastric banding procedures. After the RYGB procedure,
there was 12% total body weight loss after six months and 45% after three years. Another report
included in this study showed weight loss during the three years after RYGB to be 30-35% total
body weight loss. With this procedure, there is some weight regain until three to five years after
surgery, but then typically plateaus at 30% total body weight loss, showing weight loss
maintenance for at least 10-20 years. For the LAGB procedure, weight loss averaged 15.9% after
three years. Bariatric surgery has been found to decrease triglyceride and LDL levels while
increasing HDL levels. One notable example is three years after RYGB surgery, dyslipidemia
was decreased in 62% of the patients. For patients with type 2 DM, a study compared RYGB or
BPD surgeries with medical interventions. A person is considered in remission from diabetes if
their HbA1c level is less than or equal to 6.5% and fasting plasma glucose level is less than or
equal to 5.6 mmol/L after two years, with no pharmacotherapy within the last year. Results
showed that 50% of patients were in remission after five years if they underwent surgery. In
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contrast, zero patients who underwent medical intervention were in remission after five years.
The benefits of weight loss from bariatric surgery include: decrease in visceral adipose tissue as
well as improved dyslipidemia, hypertension, diabetes, nonalcoholic fatty liver disease,
endothelial function, and obstructive sleep apnea.24
V. Discussion
Obesity is a pervasive issue in the United States that needs resolution. This chronic issue
is often associated with various comorbid diseases that can often be improved with weight loss.
Oftentimes, weight loss does not have to be significant, and 5-10% of weight loss can
significantly improve a person’s quality of life. After considering the results of the four diet
methods selected, bariatric surgery is the most effective option for weight loss and maintenance,
which was hypothesized from the beginning. However, bariatric surgery is not available to
everyone based on their BMI and is used as a last option after all other weight loss methods have
been exhausted. Additionally, bariatric surgery is a dramatic life change and most people would
rather use other methods without putting themselves at risk for complications. A more suitable
diet plan is the Medifast program, which provides pre-made meals with the necessary nutrients
for steady weight loss. Additionally, there is the option of the Medifast Weight Control Centers,
where clients can have supervision and guidance during the process. This provides weekly one-
on-one sessions with a counselor and keeps clients accountable throughout the entire process
because they are being weighed and their progress is tracked. They are also receiving lifestyle
changes to make their weight loss life-long instead of temporary. This could keep someone
accountable and decrease the temptation of deviating from the plan. Additionally, the meal plan
is chosen that best suit the client’s lifestyle and diet wishes, making it personalized to them.
40
Unfortunately, this program can become quite expensive if the client stays in the program for an
extended period of time, such as 52 weeks, which occurred in some of these studies.
By looking at each of the diet methods individually, it can be seen that they each have
their strengths and weaknesses. Orlistat, which is the pharmacological approach to weight loss,
has been shown to cause modest weight loss, and does not necessitate a dramatic life change in
order to use it. However, there are a few downsides. These include the fact that weight regain is
common once the medication is stopped. Additionally, the medication needs a diet with a higher
fat content to be effective because of its function as a lipase inhibitor. Once the medication was
discontinued, a high fat diet would need to be decreased because the body would no longer have
the lipase inhibitor. This may be difficult for some people to make this transition. Lastly, there
are side effects including fatty and oily stools due to the fat excretion, which people may find
unpleasant, but it should be noted that these side effects tend to decrease with time.
Partial meal replacement plans are the most common type of meal replacement plan
because this allows people to still maintain a more normal lifestyle. They are still able to choose
at least one regular, healthy meal per day, while they are learning lifestyle changes from the
portion controlled meal replacements. This allows people to slowly wean themselves off the
meal replacements or decrease the number of meals they are replacing because they are learning
new food habits that can be transitioned to regular food choices. These studies showed that meal
replacements increased weight loss and decreased BMI, fat mass, waist circumference, blood
pressure, and levels of insulin, glucose, triglycerides, LDL, and total cholesterol. HDL levels
increased in some studies but not all. The protocol that seemed to work best for a partial meal
replacement plan is the one detailed in Basciani et al. (2015), which was a four-stage program
using meal replacement products and a very low calorie diet (VLCD) at the beginning, while
41
slowly adding more food to end up at a hypocaloric balanced diet (HBD). The subjects
transitioned from four or five meal replacement products in the first stage to one meal
replacement in the last stage. This allowed steady monthly weight loss with an average total
weight loss of 14.7 kg, which is a significant amount. This program allows the body to slowly
adapt to the new changes, and the hypocaloric balanced diet is feasible enough to continue into
the maintenance phase and long-term. An added benefit is that meal replacements can also cause
additional weight loss during the maintenance phase. All of these results are best coupled with
exercise throughout the weight loss intervention program and compliance with the meal
replacement plans.
Medifast, as discussed above, is effective for both weight loss and weight loss
maintenance. The limitation of the studies selected for this review are they follow the weight loss
of the subjects during the Medifast program, but not afterwards when they discontinue the
program. However, the Maintenance phase of the program sets the clients up for the future where
they are not completely dependent on Medifast meals and instills healthy habits. Programs such
as Medifast are popular weight loss options because people have the option of not doing the
work on their own through the Medifast Weight Control Centers. One of the most difficult parts
of any diet is choosing the correct foods that provide the healthy amount of nutrients, while also
maintaining the correct portion sizes. Medifast provides pre-made meals that are portion-
controlled and formulated with a healthy amount of vitamins, minerals, low fat, and protein. The
results showed not only weight loss, but also little weight regain in the maintenance phase.
Additionally, various biomarker levels were decreased to a healthier level, which decreases the
risk of disease for clients.
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Bariatric surgery is a reasonable option for people who have tried other weight loss
methods without success. When people are at the point of considering bariatric surgery, it usually
means they are morbidly obese and have tried diets, exercise, pharmacotherapy, and other
medical interventions. With this type of surgery, patients undergo extensive preoperative
assessments to ensure they are not only physically capable of this surgery, but mentally as well.
This surgery causes weight loss by physiologically changing the way the body digests and
absorbs food, as well as causing behavioral changes such as eating less because of a decrease in
appetite and feeling “full” more quickly. Though this surgery is an extensive lifestyle change, the
various types of bariatric surgery have been developed over the past few decades to minimize
surgical complications and can literally save the patient’s life by not only losing weight, but also
improving various comorbid diseases, including type 2 DM and dyslipidemia. It is important to
stress to these patients that they must also change their diet and they must know that they have to
implement lifestyle changes after this surgery. There will be some natural behavioral changes,
including the desire to eat less as noted above, but consciously eating healthy and exercising will
enhance the weight loss effects and ensure this weight loss is long-term.
43
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