![]() The amount of energy a person uses to perform daily tasks varies depending on factors such as his or her weight (the heavier a person is the more energy is required for movement) and their physical activity level. In addition to their BMR, people also use energy for movement of all types. The BMR accounts on average for about three-quarters of an individual's energy needs. Older adults usually have a lower BMR than younger people since their muscle mass tends to decrease with age. Men usually have a higher BMR than women since they tend to have more muscle. Infants and young children tend to have a proportionately high BMR for their size due to their rapid growth and development. An average adult will use around 1.1 kcal each minute just to maintain these functions and BMR differs from one person to the next, both within a population and between population groups. ![]() The basal metabolic rate (BMR) is the rate at which a person uses energy to maintain the basic functions of the body – breathing, keeping warm, and keeping the heart beating – when at complete rest. The actual amount of energy needed varies from person to person and depends on their basal metabolic rate (BMR) and how active they are. What determines how much energy a person needs? The TEF is the energy cost of digesting food and is rarely assessed separately. 1 kilocalorie (kcal) = 1,000 calories, or 1 Calorieġ kcal = 4.184 kJ, so a 1000 kcal diet provides 4.184 MJ or 4184 kJĮnergy expenditure is the sum of the basal metabolic rate (BMR) (the amount of energy expended while at rest at a neutral temperature and in the fasting state), the thermic effect of food (TEF) (otherwise known as dietary-induced thermogenesis) and the energy expended in movement of all types.Ī substantial proportion of total energy expenditure is accounted for by BMR, which is determined principally by body mass and body composition both of which vary with age and sex (see below).These days, energy intake is often measured in joules (J) (or kilojoules (kJ)) but many people are more familiar with Calories (kcal). Īpplication of these factors to the food and drink consumed enables energy intake to be estimated. Carbohydrate (starch and sugars) is the least energy dense nutrient, providing just 3.75kcal (16kJ)/g.Alcohol is the second most energy dense nutrient, providing 7kcal (29KJ)/g.Fat is the most energy dense nutrient, and provides 9kcal (37kJ)/g.The amount of energy that each of these macronutrients provides varies: This is due to factors such as sex, body size, bodyweight, climate and physical activity levels.Įnergy is obtained, from the food and drink we consume, by oxidation of carbohydrate, fat, protein and alcohol, known as macronutrients. However, daily energy requirements vary widely from one individual to the next. These include keeping the heart beating and organs functioning, maintenance of body temperature, muscle contraction and growth. To lose weight, energy expenditure must exceed intake, and to gain weight, energy intake must exceed expenditure.Ī regular supply of dietary energy is essential for life and is required to fuel many different body processes. To maintain bodyweight, it is necessary to balance the energy derived from food with that expended in physical activity.Energy expenditure is the sum of the basal metabolic rate (the amount of energy expended while at complete rest), the thermic effect of food (TEF, the energy required to digest and absorb food) and the energy expended in physical activity.Energy requirements vary from one individual to the next, depending on factors such as age, sex, body composition and physical activity level.It comes from the fat, carbohydrate, protein and alcohol the diet contains. Energy is needed by the body to stay alive, grow, keep warm and move around.
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