Saturday, 6 September 2008

Why you gain weight with age

Putting on weight - even when eating the same diet and exercising the same amount as before?

Sadly, it seems biologically inevitable that, as we get older, it's easier and easier to put on more weight - and at the same time harder and harder to lose it.

According to a recent set of answers in New Scientist to the well known question of middle age spread, it's due to a mixture of factors.

  • After age 20: resting metabolic rate decreases by 3% per decade, so your body can go on for longer and longer on the same amount of food as before (i.e., the body needs less and less food)
  • After age 45: our brain weight reduces more and more (and as we age the weight of our organs generally and muscles as well as our height reduces, though sadly it seems not enough to compensate for the weight gain from other factors!) - so there's less that needs feeding
  • Generally as we age:
    • changes in the levels of various hormones and the body's responses to them result in increased fat creation and, it seems, it also takes more to satisfy the appetite
    • we tend to do less, i.e. be less active, and
    • we need less energy to digest our food.

(There are also arguments as to why, as we age, our bodies might want to build up more fat - fat or adipose tissue being our storage tank for energy etc - for both biological and possibly evolutionary reasons, in terms of the reduced power of older people in society to access food.)

With food, diets and weight loss I think it's always basically down to just one simple broad "energy in/out" equation - if you you take in more energy than your body needs for what it expends, then you'll gain weight; if less, then you'll lose weight.

Sadly, it's now very clear that our bodies need less food as we age. So, just to maintain the same weight as you get older, you actually have to eat less or exercise more than you used to - or both.

It's kinda logical. But it doesn't seem fair, does it?

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