FAT LOSS, BIOLOGICAL INFLUENCES: AGE

New research on the effects of ageing on body fat suggest that there are a number of components of ageing which mean that gaining fat stores with age is a ‘natural’ process and that losing fat becomes more difficult. Changes with age that promote fat gain are:

• a decrease in lean body mass: and therefore a reduction in metabolic rate. This may be compensated for by such activities as resistance training, although the extent to which this can occur is not dear at this stage. Metabolic rate is thought to decrease naturally by about 2 per cent per decade after the age of 20.

• changes in fat oxidation. The rate at which the body bums fat as an energy source in contrast to blood sugars, decreases with age, possibly as a result of the increase in body fat mass. This means fat is stored more readily and used less easily as a fuel source in the elderly.

changes in the influences of stimuli which ‘break down’ fat (lipolytic stimuli). Hormones such as growth hormone and testosterone all decrease with age and catecholamines from the adrenal glands appear less effective with age. Hence, the normal status of older people promotes fat gain

As well as a decrease in physical activity (through sport and games) it now appears that even if older people consciously exercise vigorously to lose fat, they may unconsciously decrease their rate of physical activity at other times during the day: they simply get more tired than young people as a result of exercise, and unless an effort is made to maintain SPA, the net effect may be no real gain in overall physical activity.

• increased associated health conditions: heart disease, arthritis and other muscular-skeletal problems.

• a decrease in intra-muscular fat as an energy source. There are significant stores of fat in muscle tissue. The storage of fat in the muscle tissue decreases with age as the binding protein decreases. This means fat from the muscle is less readily available as an energy source during exercise and a greater reliance is placed on other energy stores.

• increased eating. Although this is often under-reported, there is evidence to suggest that eating and drinking may actually increase with age, rather than decrease or remain stable, as would be necessary to stabilise body fat. Accurate monitoring of food intake in the elderly will be necessary before this can be verified.

On the positive side, it appears that moderate fat gains with ageing do not appear to be as dangerous as those in the young and a BM up to 27kg/m2 is considered within the normal range for older people. However, this point is still hotly debated and in the meantime caution is still advised.

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