© food – a fact of life 2009 energy foundation. © food – a fact of life 2009 learning...

© Food – a fact of life 2009

Energy

Foundation


Learning objectives

• To define energy and explain why it is needed.

• To identify sources of energy in the diet.

• To understand how energy needs throughout life.

• To understand the energy needs of different levels of physical activity.

• To define energy balance and understand the consequences of imbalance.


What is energy?

Energy is the power used to do work or to produce heat or light.

Energy cannot be created or destroyed, but can be changed from one form to another.

For example, when a match is burned, the energy locked in the chemicals

is converted to heat and light.


What is energy needed for?

Our body needs energy from food to:

• stay alive;

• be active;

• grow;

• keep warm.


Energy in food and drinks

Energy is provided by the food and drinks we consume.

Food and drinks contain macronutrients – carbohydrate, protein and fat (and alcohol) which are broken down in the body to provide energy.

It is measured in joules (J) or kilojoules (kJ).



Energy is provided by the macronutrients - carbohydrate, protein, and fat, in food and drinks.

• 1 gram of carbohydrate provides 16kJ.

• 1 gram of protein provides 17kJ.

• 1 gram of fat provides 37kJ.



Alcohol also provides energy. However, it is not considered a nutrient because we do not need it to survive.

1 gram of alcohol provides 29kJ.



29

37

1617

0

5

10

15

20

25

30

35

40

Carbohydrate Protein Alcohol Fat

kJ

per gra

m

Per gram, fat provides more than twice the energy of carbohydrate.


Energy in the diet - bagel 100g

• Total Energy 1135.5kJ

• Carbohydrate 924.8kJ

• Fat 40.7kJ

• Protein 170.0kJ


Energy in the diet - oil 100g



• Fat 3696.0kJ

• Protein 0.0kJ


Energy in the diet – ham 100g



• Fat 122.1kJ

• Protein 312.8kJ


Which nutrient contributes the mostenergy in each food?

Per 100g

Total Energy

Carbohydrate

Fat Protein

Bagel 1135.5kJ 924.8kJ 40.7kJ 170.0kJ

Oil 3696.0kJ 0.0kJ 3696.0kJ 0.0kJ

Ham 450.9kJ 16.0kJ 122.1kJ 312.8kJ


Dietary reference values (DRVs)

Experts have estimated the average requirements for energy for different types of people. These figures are known as Estimated Average Requirements (EAR) for energy.

Experts also recommend that:

• about 50% of our energy intake should come from carbohydrate;

• no more than 35% of our energy intake should come from fat;

• about 15% of our energy intake should come from protein.


How much energy do we need?

Different people need different amounts of energy depending on their:

• level of activity;

• age;

• sex;

• body size.


Energy needs change throughout life

• Infants, young children and teenagers have high energy needs for their size because they are active and growing.

• There are certain times during adulthood when energy needs are increased, e.g. pregnancy and breastfeeding.

• As people get older they do not need as much energy. One of the reasons for this is because they are usually less active


Activity levels – energy used by a 60kgadult per 30 minutes of each activity

Tennis

(doubles)

627.6kJ

Walking

(briskly)

627.6kJ

Swimming

(slow crawl)

1004.6kJ

Running

(8.5min/mile)

1690.3kJ


Activity level

A sedentary lifestyle has low energy needs.

Watching television, using the computer and sitting for long periods of time, does not use up much energy.

It is important to choose activities each day that use up more energy.


Activity level

An active lifestyle has high energy needs. The diet must include adequate amounts of carbohydrate to provide sufficient energy for the body.

An active lifestyle does not necessarily mean playing competitive sport. Walking to the shops, or taking the stairs instead of the lift, also contributes to daily activity.

Athletes have very high energy needs, so their diets must be carefully planned to make sure enough energy is consumed.


Being active every day

It is recommended that children and young adults should be active for at least 60 minutes everyday, where heart rate and breathing rate are increased.

This can be as simple as brisk walking.

Not all children are meeting this target.


Being active

Adults, also need to be more physically active.

Experts recommend adults should be active for at least 30 minutes, five days a week.

Activities that increase muscle strength and flexibility, as well as bone strength should also be included once a week, e.g. running.


Energy balance

Energy balance is achieved when the energy provided by consuming food and drinks (energy in) equals the amount of energy used up by the body.

Overtime it is important to maintain energy balance to maintain a healthy weight (energy in = energy out).

The body uses up energy provided by food and drinks and from its own energy stores. Body fat is the main energy store.


Energy balance

Energy in – food and drinks

Energy out – activity

Energy in → Energy out → Stable weight


Positive energy balance

When the diet provides more energy than is needed, a person is said to be in positive energy balance.

People who are in positive energy balance over an extended period of time (i.e. they take in more energy than they use) are likely to become overweight or obese.


Positive energy balance



Energy in > Energy out = Weight gain


Negative energy balance

When the diet provides less energy than is needed, a person is said to be in negative energybalance.

This is caused by consuming less energy than required,

and/or being very active.

The person uses stored energy and loses weight over time.


Negative energy balance



Energy in < Energy out = Weight loss


Is there an ideal energy intake?

The average energy intake in the UK for young adults aged 11-14 years of age per day is:

7720 kJ for girls and 9270 kJ for boys.

However, energy needs vary from person to persondepending on their activity level.

Young adults need to find the energy intake thatkeeps them in the desirable weight range for their age.

Being either underweight or overweight causes risks to health.


Underweight

When too little energy is consumed over a period of time, the body uses fat stores which leads to weight loss.

When too much weight is lost, the body will become underweight.

People who are very underweightoften have health problems including hair loss and developing dry patchy skin.


Overweight and obesity

When too much energy is consumed or not enough energy is used by the body, energy is stored in the body as fat over a period of time.

Having too much fat in the body leads to weight problems, such as overweight and obesity.

Overweight or obesity are risk factors for manydiseases, e.g. coronary heart disease,some cancers and diabetes.


Review of the learning objectives

• To define energy and explain why it is needed.

• To identify sources of energy in the diet.

• To understand how energy needs throughout life.

• To understand the energy needs of different levels of physical activity.

• To define energy balance and understand the consequences of imbalance.


For more information visit

www.nutrition.org.uk

www.foodafactoflife.org.uk

© food – a fact of life 2009 energy foundation. © food – a fact of life 2009 learning...

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