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Energy. Foundation. Learning objectives. To define energy and explain why it is needed. To identify sources of energy in the diet. To identify energy needs of the body throughout life. To describe different levels of physical activity.
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Energy Foundation
Learning objectives • To define energy and explain why it is needed. • To identify sources of energy in the diet. • To identify energy needs of the body throughout life. • To describe different levels of physical activity. • To define energy balance and explain when energy in does not equal balance energy out.
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.
Units of measurement. Energy is: • provided by the food and drinks we consume. • provided by the macronutrients - carbohydrate, protein, and fat (and alcohol). • measured in joules (J) or kilojoules (kJ).
Where can we get energy through diet? 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.
Where can we get energy through diet? 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.
Energy (kJ) provided per gram Per gram, fat provides more than twice the energy of carbohydrate.
Energy in the diet - bagel 100g • Total Energy 1161.0kJ • Carbohydrate924.8kJ • Fat 40.7kJ • Protein 170.0kJ
Energy in the diet - oil 100g • Total Energy 3696.0kJ • Carbohydrate 0.0kJ • Fat3696.0kJ • Protein 0.0kJ
Energy in the diet – ham 100g • Total Energy 450.9kJ • Carbohydrate 16.0kJ • Fat 122.1kJ • Protein312.8kJ
Dietary reference values (DRVs) DRVs include estimated average requirements (EAR) for energy. It is 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.
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 mothers. • Older adults do not need as much energy because they are not usually as active.
Activity levels – Energy used by a60kg adult being active for 30 minutes Tennis (doubles) 627.6kJ Walking (briskly) 627.6kJ Swimming (slow crawl) 1004.6kJ Running (8.5min/mile) 1690.3kJ
Activity level Asedentary lifestyle has low energy needs. Watching television, and sitting for extended periods of time, does not use a lot of energy. It is important to make sure not too much energy is consumed to reduce the risk of weight gain.
Activity level Anactive lifestyle has high energy needs. The diet must include adequate amounts of carbohydrates 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.
Do people need to be more active? Yes! It is recommended that children and young adults need to participate in at least 60 minutes of moderate intensity everyday, where heart rate and breathing rate are increased. This can be as simple as brisk walking. Not all children are meeting this target. Adults, also need to be more physically active. 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 where the food and drink consumed (energy in) equals the amount of energy used (energy out). It is important to maintain energy balance to maintain a healthy weight (energy in = energy out). Ideally, the amount of food eaten should provide enough energy to complete daily actives without having too much or too little energy left over. The body can obtain energy by eating a diet high in energy or by using energy stores in the body. Fat is the main store of energy used by the body.
Energy balance Energy in – food and drink Energy out – activity Energy in = Energy out = Stable weight
Positive energy balance When the diet provides more energy than is needed, it is called positive energy balance. People who have a 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 out – activity Energy in – food and drink Energy in > Energy out = Weight gain
Negative energy balance When the diet provides less energy than is needed, it is called 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.
Negative energy balance Energy in – food and drink Energy out – activity 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 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 has negative impacts on 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 underweight often have problems with losing hair and 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 the risk factors for many diseases, 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 identify energy needs of the body throughout life. • To describe different levels of physical activity. • To define energy balance and explain when energy in does not equal balance energy out.
