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A history of fad diets

Which diets are designed for weight loss?

Which diets have a scientific basis?


You are what you eat!

When food is digested its components enter the blood.

Molecules used for growth and repair become part of the body.

Those used as energy sources are lost as CO2 and H2O.

protein

glucosecarbohydrate

fat fatty acids + glycerol

amino acids


What are cells made from?

Different nutrients are incorporated into each part of a cell:

nucleus: protein

membrane: fats and carbohydrate

cytoplasm: protein and water


You are what you eat!

What could this food label represent? A human!


Different nutrients


The amount of each type of nutrient a person needs varies between individuals. What factors might affect how much a person needs?

Dietary guidelines

carbohydrate (50%)

vitamins and minerals (1%) protein

(14%)

fat (35%)


A protein deficiency illness called Kwashiorkor can cause a swollen belly and weak immune system, and is common in developing countries.

Proteins in meat and fish are called first-class proteins because they contain all the essential amino acids that humans need in their diet.

Lack of protein

What is the RDA of protein for a 60 kg student?

Recommended daily allowance (RDA) of protein (g)= 0.75 x body mass (kg)

RDA = 0.75 x 60 kg

= 45 grams


Why do some people need more food?

Metabolism is the series of chemical reactions or ‘life processes’ in the body. Different amounts of energy are used in different life processes.

exercise andwarmth (20%)

digestion (10%)

growth andrepair (70%)

Metabolic rate is the rate at which cells uses energy, and this varies between individuals. Why does metabolic rate increaseduring exercise and cold weather?


Chemical and physical digestion


Enzymes digest food in the mouth, stomach and small intestine.

Enzymes at work

Enzymes break down large food molecules into smaller ones that can be absorbed by the blood. This is called chemical digestion.

Different types of food are broken down by different enzymes.


Enzymes of digestion


Helping enzymes

Enzymes are not the only substances involved in chemical digestion.

Bile is a substance produced by the liver and stored in the gall bladder. It helps the digestion of fats by turning them into small droplets. This is called emulsification. How does this help lipase enzymes?

Hydrochloric acid in the stomach provides the right conditions for protease enzymes to break down protein.

The smaller droplets have a larger surface area, which speeds up the rate at which lipase digests the fat.


Which enzyme?


What is BMI?

Body Mass Index (BMI) measures the relative amounts of fat and muscle in the body.

BMI = body mass (kg) (height)2 (m)

underweight

normal

overweight

obese

<20

20-25

25-30

>30

BMI Conclusion

Obese people have an increased risk of arthritis, diabetes and heart disease. People who are underweight tend to have poor immune systems and often get ill.

What are their health risks?

Zak:

BMI = 191.85 m and 66 kg

Gloria:

BMI = 311.45 m and 66 kg


Are you right for your height?

This means it is helpful to use extra measures to help judge how healthy a person is, such as waist circumference.

This is because muscle is denser than fat.

Calculating a person’s BMI can be useful, but the formula can overestimate the proportion of body fat in people who are muscular.

In 2002, 22% of boys and 28% of girls aged 2-15 in the UK were overweight or obese. Statistics show that obesity levels, among both young people and adults, are rising.


Blood pressure is a measure of the pressure exerted by the blood against artery walls. Blood pressure varies with:

What is blood pressure?

Blood pressure is measured as two numbers, e.g. 120/80. What do these numbers show?

The numbers show pressure readings in mm of mercury.

heartbeat strength blood volume fitness

health age.


The big number (‘120’) is the systolic pressure. This is the blood pressure during a heartbeat.

“Blood pressure one-twenty over eighty.”

Systolic and diastolic

The small number (‘8’) is the diastolic pressure. This is the blood pressurein-between heartbeats.


How does blood pressure affect health?

Low blood pressure can cause dizziness, fainting and poor circulation.

High blood pressure can make blood vessels more likely to burst, and can cause strokes and kidney damage.

80-100

90-110

110-125

130-150

10

15

20

40

Age Systolic Diastolic

60

60

70

80

The older you get, the higher your blood pressure naturally becomes.

Kevin is 38 years old and his blood pressure is 180/90. What advice would you give him?


Lifestyle assessment

Kevin’s GP quizzed him about his lifestyle, tested his blood and referred him to a health centre.

What else could Kevin do to improve his health?

Excess salt is known to increase blood pressure in about 30% of the population.


Health and physical fitness are different.

Kevin’s GP wants his cardiovascular fitness to improve so that he puts less strain on his body. His personal trainer wants other sorts of fitness to improve.

Health and fitness

What types of exercise should Kevin do?

A healthy person is free from disease or abnormality.

A fit person has good cardiorespiratory, aerobic and muscular endurance.


Fast food and takeaways such as curries, burgers and pizzas are high in unhealthy nutrients such as saturated animal fats, sugar and salt.

Fast food usually contains very little fibre, vitamins, minerals or unsaturated vegetable oils, which are important for a healthy diet.

What is wrong with fast food?


Unhealthy diets?


Cholesterol levels depend on diet and genes, but high levels of LDL have been linked to eating lots of saturated fats and few mono/polyunsaturated fats.

What is cholesterol?

Cholesterol is a lipid found in cell membranes and is used in the production of hormones and bile.

high-density lipoprotein (HDL): often called ‘good cholesterol’

low-density lipoprotein (LDL): often called ‘bad cholesterol’.

Cholesterol is transported in the blood by molecules called lipoproteins, of which there are two types:


Good and bad cholesterol

How do ‘good’ and ‘bad’ cholesterol affect a person’s health?


Excess LDL is deposited on the walls of blood vessels, which can lead to clots in the arteries. This can starve the heart of oxygen and cause heart disease.

HDL returns cholesterol to the liver where it is metabolized.

Cholesterol and heart disease

The risk of heart disease may be reduced by:

Why is LDL called ‘bad cholesterol’?

Why is HDL called ‘good cholesterol’?

lowering blood cholesterol eating more HDL than LDL gentle daily exercise.


Kevin’s blood test showed high cholesterol, but not high enough to require drug therapy to reduce it.

Should Kevin buy the margarine?What extra information would help him decide?

This margarine claims to cut blood cholesterol by 10%, but it costs four times as much as normal margarine.

Taking action


The plant extracts in margarine that lower cholesterol are less effective than cholesterol-lowering drugs called statins. Should these drugs be available without a prescription?

What do you think?

No! People with normal cholesterol might take them and they wouldn’t be checked

for side-effects like liver damage.

What are statins?

Yes! People should be allowedto self-medicate.


blood pressure – The pressure in the arteries during and between contractions of the heart.

body mass index – A measure of a person’s weight in relation to their height.

chemical digestion – The process of breaking large food molecules into smaller ones using enzymes.

fitness – Strength, stamina, flexibility, agility, speed and cardiovascular efficiency.

health – Freedom from disease and injury.

heart disease – An abnormal condition of the heart or the arteries that supply the heart.

Glossary (1/2)


lipoproteins – Molecules that carry cholesterol in the blood and which are either high density or low density.

metabolic rate – A measure of how fast chemical reactions occur in cells.

obese – A person who is very overweight and has a BMI of over 30.

physical digestion – The breaking up of pieces of food by chewing it in the mouth and churning it in the stomach.

saturated – A type of animal fat that raises blood cholesterol levels and increases the risk of heart disease.

unsaturated – A type of fat from vegetable and fish oils that helps lower blood cholesterol levels and reduce the risk of heart disease.

Glossary (2/2)


Anagrams


Multiple-choice quiz

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Documents

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