Energy expenditure and its measurement
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. • It is the energy that the person would use simply lying in bed all day
The body uses up energy to digest, absorb and metabolise food. People on a high-fat diet will use less energy on digestion than someone on a healthier high-carbohydrate diet. Thermic affect of food
Energy expended above resting to move about etc. It is the most variable component of energy expenditure A heavier person uses up more energy to perform the activity Physical activity
This table Shows some typical values of the energy cost of variable activities:
To lose weight, try skipping Pick up a rope and get skipping: a new study has found that it’s one of the most effective types of exercise for suppressing hunger, says the Daily Mail. For a study in Japan, researchers recruited 15 male volunteers, and gave them a series of exercises which involved skipping or cycling on a static bicycle. At other times, they did nothing. Throughout the exercises they were tested for levels of hormones known to be involved in controlling appetite, and asked how hungry they felt (all had fasted beforehand). The results showed that the men were less hungry after skipping than cycling, and both activities left them less hungry than doing no exercise at all. Skipping was also found to have lowered the levels of hormones that stimulate hunger – but the difference between the skippers and the cyclists was minimal, suggesting that another process is involved. Possibly, said the researchers, the up and down activity involved in load-bearing exercise like skipping (as opposed to non-load-bearing exercise such as swimming) disturbs the gut in such a way as to affect appetite.
Fact - only a third of adults manage 30 minutes of physical activity at least once a week, and that the number of people admitted to hospital with a primary diagnosis of obesity tripled between 2006-7 and 2011-12, to 11,740. The majority of these admissions were for surgery.
Factors affecting total energy expenditure • Body size and composition • Age • Size • Nutritional status • Pregnancy and lactation • Activity • climate
Measurement of BMR • Measure 12-18 hrs after eating • At complete physical and mental rest • In a comfortable environment • Free from anxiety
Direct Calorimetry • All the energy produced by BMR result in heat production • Measurement of heat produced gives a measure of the energy released • Heat production is measured using a direct calorimeter
Indirect Calorimetry • Since 95% of energy production in the body depends on the process of oxygen, it follows that the measurement of the oxygen consumed by the body over a period of time gives an indirect measure of energy expenditure. This is known as indirect calorimetry.
Portable respirometers allow energy expenditure during occupationall and sporting activities
Heart rate recording • In any individual there is a relationship between heart rate and oxygen consumption during any activity above resting. • The greater the oxygen consumption, the higher the heart rate