© Food – a fact of life 2009 Energy Foundation

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 What is energy needed for? Our body needs energy from food to: stay alive; be active; grow; keep warm.

© Food – a fact of life 2009 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).

© Food – a fact of life 2009 Energy in food and drinks 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.

© Food – a fact of life 2009 Energy in food and drinks 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.

© Food – a fact of life 2009 Energy in food and drinks Per gram, fat provides more than twice the energy of carbohydrate.

© Food – a fact of life 2009 Energy in the diet - bagel 100g Total Energy1135.5kJ Carbohydrate924.8kJ Fat40.7kJ Protein170.0kJ

© Food – a fact of life 2009 Energy in the diet - oil 100g Total Energy3696.0kJ Carbohydrate0.0kJ Fat3696.0kJ Protein0.0kJ

© Food – a fact of life 2009 Energy in the diet – ham 100g Total Energy450.9kJ Carbohydrate16.0kJ Fat122.1kJ Protein312.8kJ

© Food – a fact of life 2009 Which nutrient contributes the most energy in each food? Per 100g Total Energy CarbohydrateFatProtein Bagel1135.5kJ924.8kJ40.7kJ170.0kJ Oil3696.0kJ0.0kJ3696.0kJ0.0kJ Ham450.9kJ16.0kJ122.1kJ312.8kJ

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 How much energy do we need? Different people need different amounts of energy depending on their: level of activity; age; sex; body size.

© Food – a fact of life 2009 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

© Food – a fact of life 2009 Activity levels – energy used by a 60kg adult per 30 minutes of each activity Tennis (doubles) 627.6kJ Walking (briskly) 627.6kJ Swimming (slow crawl) kJ Running (8.5min/mile) kJ

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 Energy balance Energy in – food and drinksEnergy out – activity Energy in → Energy out → Stable weight

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 Positive energy balance Energy in – food and drinks Energy out – activity Energy in > Energy out = Weight gain

© Food – a fact of life 2009 Negative energy balance When the diet provides less energy than is needed, a person is said to be in negative energy balance. This is caused by consuming less energy than required, and/or being very active. The person uses stored energy and loses weight over time.

© Food – a fact of life 2009 Negative energy balance Energy in – food and drinks Energy out – activity Energy in < Energy out = Weight loss

© Food – a fact of life 2009 Is there an ideal energy intake? The average energy intake in the UK for young adults aged years of age per day is: 7720 kJ for girlsand9270 kJ for boys. However, energy needs vary from person to person depending on their activity level. Young adults need to find the energy intake that keeps them in the desirable weight range for their age. Being either underweight or overweight causes risks to health.

© Food – a fact of life 2009 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 underweight often have health problems including hair loss and developing dry patchy skin.

© Food – a fact of life 2009 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 many diseases, e.g. coronary heart disease, some cancers and diabetes.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 For more information visit