Energy Silent Reading Pg 56 - 63

© Food – a fact of life 2009

EnergySilent Reading Pg 56 - 63

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Learning objectives

• To define energy and explain why it is needed.

• To identify sources of energy in the diet.

• To understand how energy needs change throughout life.

• To understand the energy needs of different activities.

• To define energy balance.

• To explain problems associated with energy 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.

It is measured in kilojoules (kJ) or megajoules (MJ).

When using imperial measurements, kilocalories (kcal) are used.

1kJ = 1000J1MJ = 1000kJ1kcal = 1000cal1kcal = 4.18kJ


Energy from food

When we consume food and drink, energy provided by carbohydrate, protein, and fat (and alcohol) is metabolised and used by our bodies.

Carbohydrate, protein, and fat (and alcohol) are broken down into smaller compounds which are then oxidised in the cells of the body (respiration).


Energy providing nutrients

Energy in the diet is provided by the nutrients carbohydrate, protein, and fat.

1 gram of carbohydrate provides16kJ.

1 gram of protein provides17kJ.

1 gram of fat provides 37kJ.


Energy in the diet - alcohol

Alcohol also provides the body with energy.However, it is not considered a nutrient, because it is not essential for survival.

1 gram of alcohol provides 29kJ.

People who regularly consume excessive amounts of alcoholic drinks derive much of their energy intake from alcohol. They may also suffer from nutritional deficiencies and alcohol related diseases, e.g. liver disease and Warnicke-Korsakoff syndrome.


Energy in the diet

The energy provided by a food or drink depends on the amount of carbohydrate, protein, alcohol and fat it contains.

Gram for gram, carbohydrate provides less energy than protein, fat and alcohol.

Look closely at the following examples of foods high in carbohydrate, fat and protein.


Energy in the diet - white bread 100g

Total energy 931.0kJ

Carbohydrate 737.6kJ

Fat 59.1kJ

Protein 134.3kJ


Energy in the diet - butter 100g


Carbohydrate 0.0kJ

Fat 3052.5kJ

Protein 8.5kJ


Energy in the diet – canned tuna 100g


Carbohydrate 0.0kJ

Fat 22.2kJ

Protein 399.5kJ


Which nutrient contributes themost energy?

Per 100g Energy Carbohydrate

Fat Protein

White bread

931.0kJ 737.6kJ 59.1kJ 134.3kJ

Butter 3061.0kJ

0.0kJ 3052.5kJ 8.5kJ

Canned tuna

421.7kJ 0.0kJ 22.2kJ 399.5kJ

Picture


Energy intakes

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 recommended 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.


Energy intakes

The average energy intake in the UK for young people

aged 15 - 18 years is:• 8830 kJ for girls.• 11510 kJ for boys.

However, requirements vary from person to person depending on a variety of factors, including physical activity level.


Energy expenditure

Different people need different amounts of energy, depending on a variety of factors, including their:

• basal metabolic rate (BMR);• level of physical activity;• age;• sex;• body size.


Basal metabolic rate

The basal metabolic rate (BMR) is the rate at which aperson uses energy to maintain the basic functions ofthe body e.g. breathing. BMR is measured when a person is at complete rest, and varies between person to person.

Men usually have a higher BMR than women becausethey tend to have a larger muscle mass.

The BMR accounts for 75% of an individual’s energyneeds.


Activity levels

The total amount of energy required by an individual depends on their level of activity.

The more active an individual is, the more energy they need.


Being active everyday

It is recommended that children andyoung people participate in at least 60 minutes of moderate intensity everyday where breathing rate and heart rate increase.

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

Regular activity will help maintain energy balance.


Energy needs of children

Infants and children have relatively large energy requirements because they are active and growing.

Infants and young children have a higher BMR in relation to their size because energy is needed for growth.


Energy needs of adolescents

Adolescents have high energy requirements due to the body changes they experience from 11-18 years of age.

They are also often very active.


Energy needs of adults (19-50 years)

Adult energy requirements are lower than those of adolescents.

However, during pregnancy and lactation (breastfeeding) there is an increased need for energy for the growing fetus and milk production.


Energy needs of adults 50 years and over

Energy requirements decrease gradually after the age of 50 years in women and 60 years in men.

It is advisable that older people consume food and drinks that are low in energy but high in vitamins and minerals to meet their requirements. These foods are known as nutrient dense foods.


Energy balance

To maintain body weight it is necessary to balance the energy derived from food with that expended in activity.

Energy balance is achieved when energy intake equals energy expenditure.

It is important to maintain a healthy weight or avoid becoming overweight or underweight, both of which are major public health problems in the UK.


Positive energy balance

When the diet provides more energy than is needed, it is stored as fat and the person puts on weight over time.

People who are in positive energy balance over an extended period of time (i.e. they take in more

energythan they use) are likely to become overweight or obese.


Overweight and obese

Excess energy is stored in adipose tissue and can build up if energy intake continues to be too high, or activity levels remain too low.

Being overweight or obese is associated with an increased risk of developing certain cancers, cardiovascular disease and type 2 diabetes.


Negative energy balance

A person is said to be in negative energy balance when there is insufficient energy from the diet to meet energy demands of the body.

Energy is derived from energy stores and the person looses weight.

People who achieve a negative energy balance over an extended period of time, are likely to become underweight.


Underweight

When too little energy is consumed over a period of time, the body derives energy from fat stores leading to weight loss.

When too much fat is lost, the person becomes underweight.

Being underweight is associated with health problems, such as osteoporosis, infertility and heart failure.


Monitoring energy balance

For adults, change in weight is a good guide to energy balance.

The Body Mass Index (BMI) is a good indicator of whether a person is underweight, overweight or a healthy weight.

The BMI range should only be used for people aged 18 years of age and over.

We are all encouraged to maintain a healthy weight by balancing energy intake with energy expenditure.


Calculating BMI

Step 1 Height in meters (m) x height in metres (m)

Step 2 Divide weight in kilograms (kg) by step 1

Step 3 Equals BMI. Next refer to guide below.

kg . m2

Recommended BMI rangeUnderweight less than 18.5Normal 18.5 - less than 25Overweight 25 - less than 30Obese 30 - 40Very obese over 40


Calculating BMI

Calculate these 3 examples:

kg . m2

1. Samantha

Height: 1.70m

Weight: 51kg

2. Dale

Height: 1.95m

Weight: 82kg

3. Ruth

Height: 1.63m

Weight: 78kg

BMI =



BMI example 1

51kg . 1.7m x 1.7m

BMI = 17.6

Samantha

Height: 1.70m

Weight: 51kg

Samantha is underweight.



BMI example 2

82kg . 1.95m x 1.95m

BMI = 21.6

Dale

Height: 1.95m

Weight: 82kg

Dale is a healthy weight.

Recommended BMI rangeUnderweight less than 18.5Normal 18.5 - less than 25Overweight 25- less than 30Obese 30- 40Very obese over 40


BMI example 3

78kg . 1.63m x 1.63m

BMI = 29.4

Ruth

Height: 1.63m

Weight: 78kg

Ruth is overweight.

Recommended BMI rangeUnderweight less than 18.5Normal 18.5 - less than 25Overweight 25- less than 30Obese 30- 40Very obese over 40


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 change throughout life.

• To understand the energy needs of different activities.

• To define energy balance.

• To explain problems associated with energy imbalance.


EnergyExam Style Questions Pg 64

Extension


For more information visit

www.nutrition.org.uk

www.foodafactoflife.org.uk

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Energy Silent Reading Pg 56 - 63