Biology presentation

1. Biology presentation The Effect of Exercise on Body Composition and Weight Control Jaclyn McMurray

2. Energy Expenditure and it’s measurements: • Basal Metabolic Rate • Thermic Effect of Food • Physical Activity

3. Basal Metabolic Rate (BMR) • This is the energy expended in the resting, fasting state and is the energy required to carry out normal body functions such as breathing. • This is the energy that would be used by a person lying in bed all day. • It is the largest component of an average individual’s energy expenditure and in sedentary adults accounts for 60-70% of total energy output.

4. The Main Factors Affecting BMR in an Individual are: • Body Size and Composition: BMR increases as body weight increases – the more tissue present, the more energy is expended. • Age: BMR per kg body weight is higher in children owing to the energy cost of growth, but from 18-20 years, BMR per kg decreases at the rate of about 2% decade. This age-related fall is partly due to the changing body composition as we get older – the tendency to put on extra fat with the loss of lean tissue usually as a result of becoming less physically active.

5. Thermic Effect Of Food • The body uses up energy to digest, absorb, metabolise and store ingested nutrients. Depending on the quantity and composition of the food eaten, energy expenditure may increase as much as 30% above basal in two to three hours following a meal. Over a twenty-four hour period, the thermic effect of food accounts for about 10% of the total energy expended.

6. The thermic response to a meal can vary considerably depending on the quantity and type of food eaten. For example, The thermic response can very from 17% increase in energy expenditure for a high protein meal, to a 9% increase for a high carbohydrate meal to only 3% for a high fat meal. • This means that people on a high fat diet will not use up as much energy to digest and absorb food as someone on a healthier high carbohydrate diet. This highlights one of the many dangers of a high fat diet.

7. Physical Activity • This is the energy expended above resting to move about and perform tasks such as sitting, standing, walking, running and lifting etc. • It is the most variable of the components of energy expenditure, accounting for about 30% of total energy output in sedentary individuals, up to more than 50% in those engaged in heavy manual work or vigorous training programmes.

8. This table Shows some typical values of the energy cost of variable activities:

9. Note that a heavier person uses up more energy to perform an activity due to the extra effort required to move a heavier body. • The energy cost of an activity is often expressed as a multiple of BMR, known as a physical activity ratio or PAR. For example, lying at rest.

10. Here are some other activities:

11. Physical activity is the biggest single component of the total energy expenditure which can be changed voluntarily, and is likely to be the main reason for the individual differences in energy requirements. • The energy required for physical activity of any kind depends on several variables such as intensity and the duration of the activity and the muscle masses involved.

12. When considering the influence of physical activity on energy expenditure, it is important to distinguish between short bursts of strenuous activity and moderate activity of relatively long duration. For example, a thirty-minute game of squash at 42kJ/min would use 1260 kJ whereas a three-hour round of golf at 16.7kJ/min would use 3010 kJ

13. The End