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Energy. Extension. Learning objectives. To define energy and explain why it is needed. To identify sources of energy in the diet. To identify the body’s energy needs. To describe energy needs throughout life. To explain different activity levels. To define energy balance.
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Energy Extension
Learning objectives • To define energy and explain why it is needed. • To identify sources of energy in the diet. • To identify the body’s energy needs. • To describe energy needs throughout life. • To explain different activity levels. • 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 = 1000J 1MJ = 1000kJ 1kcal = 1000cal 1kcal = 4.18kJ
Examples of energy 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).
Where does energy come from? 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. For people who drink a lot of alcohol, it may form a large part of their energy intake. This may lead to nutritional deficiencies and several alcohol related diseases, e.g. liver disease and Warnicke-Korsakoff syndrome or beri beri.
Energy in the diet The energy provided by a food depends on how many grams of carbohydrate, protein and fat are present. 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 foods.
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 Total energy 3061.0kJ Carbohydrate 0.0kJ Fat 3052.5kJ Protein 8.5kJ
Energy in the diet – canned tuna 100g Total energy 422.0kJ Carbohydrate 0.0kJ Fat 22.2kJ Protein 399.5kJ
Dietary reference values (DRVs) 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 a person uses energy to maintain basic functions of the 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 because they tend to have a larger muscle mass. The BMR accounts for 75% of an individual’s energy needs.
Activity levels The total amount of energy required by an individual depends on their level of activity. The more active they are, the more energy they need.
Do people need to be more active? Yes! Children and young people need to 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 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. Energy needs for female and male adolescents will differ slightly as changes in their development occur at slightly different ages.
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 infant.
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. The food and drink these people consume need to be lower in energy and higher in vitamins and minerals to meet their requirements. This is called nutrient dense food.
Energy balance If an adult takes in the right amount of energy from food and drink to meet their needs, they will remain the same weight. This is called energy balance, where energy intake equals energy expenditure. This should be achieved over a period of time to maintain a healthy weight. 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 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.
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. Increasing levels of overweight and obesity are associated with an increased risk of developing certain cancers, cardiovascular disease and type 2 diabetes.
Negative energy balance When the diet does not provide the energy needed, negative energy balance is achieved. The person uses their stores of energy and loses 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 by the body over a period of time, the body uses fat stores leading to weight loss. When too much fat is used by the body, the body becomes underweight. This can be associated with health problems, e.g. 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 if 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 input and energy expenditure.
Calculating BMI kg . m2 Step 1 Height in meters (m) x height in meters (m) Step 2 Divide weight in kilograms (kg) by step 1 Step 3 Equals BMI. Next refer to guide below. Recommended BMI range Underweight less than 18.5 Normal 18.5 - less than 25 Overweight 25 - less than 30 Obese 30 - 40 Very obese over 40
Calculating BMI Calculate these 3 examples: 1. Samantha Height: 1.70m Weight: 51kg 2. Dale Height: 1.95m Weight: 82kg 3. Ruth Height: 1.63m Weight: 78kg Recommended BMI range Underweight less than 18.5 Normal 18.5 - less than 25 Overweight 25 - less than 30 Obese 30 - 40 Very obese over 40 kg . m2 BMI =
BMI example 1 Samantha Height: 1.70m Weight: 51kg 51kg . 1.7m x 1.7m BMI = 17.5 Samantha is underweight. Recommended BMI range Underweight less than 18.5 Normal 18.5 - less than 25 Overweight 25 - less than 30 Obese 30 - 40 Very obese over 40
BMI example 2 Dale Height: 1.95m Weight: 82kg 82kg . 1.95m x 1.95m BMI = 21.5 Dale is a healthy weight. Recommended BMI range Underweight less than 18.5 Normal 18.5 - less than 25 Overweight 25- less than 30 Obese 30- 40 Very obese over 40
BMI example 3 Ruth Height: 1.63m Weight: 78kg 78kg . 1.63m x 1.63m BMI = 29 Ruth is overweight. Recommended BMI range Underweight less than 18.5 Normal 18.5 - less than 25 Overweight 25- less than 30 Obese 30- 40 Very 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 identify the body’s energy needs. • To describe energy needs throughout life. • To explain different activity levels. • To define energy balance. • To explain problems associated with energy imbalance.
