There are a number of contributing factors at work here. As we age we tend to reduce our active pursuits and, above the age of 20, our resting metabolic rate reduces by about3 per cent per decade, allowing our bodies to go further and further on the same amount of food. On top of this, as we age, we use less energy to digest and process the food that we eat.rnThere are also hormonal changes that encourage fat build-up. A decrease in levels of growth hormone and testosterone contribute to an increase in fat mass. Additionally there is a reduced response to hormones produced in the thyroid gland, which stimulate metabolism of lipids and carbohydrates, and possibly also to leptin, which helps to control appetite.
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