© Food – a fact of life 2009 Energy Extension

© 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 change throughout life. To understand the energy needs of different activities. To define energy balance. To explain problems associated with energy 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. 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

© Food – a fact of life 2009 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).

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 Energy in the diet - white bread 100g Total energy931.0kJ Carbohydrate737.6kJ Fat59.1kJ Protein134.3kJ

© Food – a fact of life 2009 Energy in the diet - butter 100g Total energy3061.0kJ Carbohydrate0.0kJ Fat3052.5kJ Protein8.5kJ

© Food – a fact of life 2009 Energy in the diet – canned tuna 100g Total energy421.7kJ Carbohydrate0.0kJ Fat22.2kJ Protein399.5kJ

© Food – a fact of life 2009 Which nutrient contributes the most energy? Per 100gEnergyCarbohydrateFatProtein White bread 931.0kJ737.6kJ59.1kJ134.3kJ Butter kJ0.0kJ3052.5kJ8.5kJ Canned tuna 421.7kJ0.0kJ22.2kJ399.5kJ Picture

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 Energy intakes The average energy intake in the UK for young people aged years is: 8830 kJ for girls kJ for boys. However, requirements vary from person to person depending on a variety of factors, including physical activity level.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 Basal metabolic rate The basal metabolic rate (BMR) is the rate at which a person uses energy to maintain the 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 Being active everyday It is recommended that children and young 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 Energy needs of adolescents Adolescents have high energy requirements due to the body changes they experience from years of age. They are also often very active.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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 energy than they use) are likely to become overweight or obese.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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.

© Food – a fact of life 2009 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. m 2 Recommended BMI range Underweightless than 18.5 Normal less than 25 Overweight25 - less than 30 Obese Very obeseover 40

© Food – a fact of life 2009 Calculating BMI Calculate these 3 examples: kg. m 2 1. Samantha Height: 1.70m Weight: 51kg 2. Dale Height: 1.95m Weight: 82kg 3. Ruth Height: 1.63m Weight: 78kg BMI = Recommended BMI range Underweightless than 18.5 Normal less than 25 Overweight25 - less than 30 Obese Very obeseover 40

© Food – a fact of life 2009 BMI example 1 51kg. 1.7m x 1.7m BMI = 17.6 Samantha Height: 1.70m Weight: 51kg Samantha is underweight. Recommended BMI range Underweightless than 18.5 Normal less than 25 Overweight25 - less than 30 Obese Very obeseover 40

© Food – a fact of life 2009 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 range Underweightless than 18.5 Normal less than 25 Overweight25- less than 30 Obese Very obeseover 40

© Food – a fact of life 2009 BMI example 3 78kg. 1.63m x 1.63m BMI = 29.4 Ruth Height: 1.63m Weight: 78kg Ruth is overweight. Recommended BMI range Underweightless than 18.5 Normal less than 25 Overweight25- less than 30 Obese Very obeseover 40

© 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 change throughout life. To understand the energy needs of different activities. To define energy balance. To explain problems associated with energy imbalance.

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