Healthy Eating Club Courses 
The total amount of energy your body uses daily
(total energy expenditure) depends on:
1. Your Basal Metabolic Rate at rest (BMR) (50-70%)
Accounts for 50-70% of the energy your body uses
i.e. around 1200-1400 calories per day are required in females, and 1400-1800 calories in males to keep basic body processes going (e.g. breathing).Factors which can alter your BMR:
genes - you may inherit a slow or fast BMR from your parents, grandparents etc.
age - older adults have a slower BMR than younger adults due to loss of muscle mass.
gender - women have a slower BMR than men due to less muscle mass.
muscle mass - the more muscle mass you have the higher your BMR because muscle uses a lot more energy than fat tissue.
exercise - increases BMR directly and via its effect on muscle mass.
crash diets/starvation - can reduce your BMR by up to 45%.
hot or cold environmental temperatures - can increase BMR because the body has to work harder to maintain body temperature within the normal range.
illness/surgery - can increase BMR.
accounts for 20% of energy your body uses
This is the second largest component of the total amount of energy your body uses daily and is the energy spent in operating voluntary muscles; for some athletes it may be the main user of energy.
accounts for 10-20% of energy your body uses; thermic effect highest for protein (30%),
then carbohydrate (6%) and lowest for fat (4%).
It costs energy to digest food and accounts for 10% of total energy expenditure; this energy has to be deducted from the overall energy content of the food itself.To read a short on-line article on metabolic rate go to:
http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/foodfacts?OpenView&Count=500
Audio Transcripts
This is the energy expended while resting quietly. It is the metabolic cost of maintaining the body at rest and accounts for 50-70% of total energy expenditure in most individuals. Total lean mass, especially muscle mass, is largely responsible for the BMR. So anything which reduces lean mass will reduce BMR. It is therefore important to preserve muscle mass when trying to lose weight. Exercise uses energy directly and maintains lean body mass, particularly muscle mass, thus maintaining BMR that determines a significant proportion of total energy expenditure.
Crash diets can also reduce the metabolic rate, mainly because of their effect on muscle mass. The greater the muscle mass, the higher the metabolic rate and hence calories burnt. Severe energy restriction for weight loss <1200kcal/day (especially if it is not accompanied by increased physical activity), can result in rapid weight loss. But what is often not understood is that most of the lost weight is fluid and muscle tissue. Soon the body takes steps to regain the lost water and weight begins to rise causing frustration and disappointment. The rapid loss in weight is seen by the body as a 'famine' situation. In a concerted effort to survive, the body dramatically reduces its metabolic rate within 24-48 hours from the commencement of dieting. The reduction in basal metabolic rate may be as high as 45 %. It becomes difficult to maintain the initial exaggerated rate of weight loss, especially if exercise is not increased. Food intake needs to be further decreased for a continuing weight loss. Eventually the crash dieter gives up in frustration as the energy restriction becomes ridiculously low. Repeated bouts of severe energy restriction (without accompanying daily exercise) can have a long term effect on weight loss and the metabolic rate. The body adapts to these constant periods of 'cyclic fasting' by depressing the metabolic rate to conserve energy. The result is that diets become progressively less effective and because they can lower your metabolic rate, they have the potential to increase your risk of gaining weight even at moderate energy intakes. Thus the expression "Diets can make you fat".
One of the controls we have over total energy expenditure is to increase exercise. Physical activity has heat-producing (thermogenic) effects, which raises the metabolic rate to a much greater extent than the thermic effects of food intake or exposure to cold. Apart from the energy used in the exercise itself, habitual physical activity affects basal metabolic rate by virtue of its effect on body composition. A study showed that habitually active individuals have higher BMRs than non-active individuals, by as much as 5-10%. Since BMR accounts for approximately two thirds of total daily energy expenditure, this is a significant difference.
The thermic effect of food is the energy we use to process/metabolise the food we consume. It is a component of energy expenditure that can be directly manipulated by altering the ratio of macronutrients of the diet. As the carbohydrate and protein content increases and the fat content decreases the thermic effect of food rises; this energy wastage may assist in the maintenance of normal weight. The greatest energy wastage occurs for protein where 30% of its calorie value is used for its metabolism, in contrast the value is 6% for carbohydrate and only 4% for fat. In other words only 4% of the calorie value of the fat consumed will be used for digestion and metabolism resulting in a low thermic effect - this partly explains why dietary fat is the most 'fattening' of the macronutrients. There is now evidence that certain factors in food, like capsaicins in chillis, may increase the background thermogenic response to food; this can ultimately increase total daily energy expenditure. This phenomenon may possibly account for different proneness to obesity in different food cultures.
