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How do we store fat?

How does our body store fat? Fat, (adipose tissue) is found in several places in the body, generally underneath the skin (subcutaneous fat). There is also some fat surrounding your vital organs for protection. An adult man tends to carry body fat in his chest and abdomen, producing an “apple” shape whereas women will carry fat in their breasts, hips, waist and buttocks, creating a “pear” shape. The difference in fat location comes from the sex hormones oestrogen and testosterone.

Generally there are three fat layering periods when the body is much more inclined to convert excess energy from the diet into fat cells. These periods are: during the third trimester of pregnancy as the foetus is developing; between nine and eighteen months of age; and at onset and duration of puberty. If there are significant excess calories present during these “layering periods”, then more fat cells will be produced (hyperplasic adiposity) and this means more fat cells for life!

It was always thought that following these fat layering periods, the number of fat cells was set for life, and that as we overeat, these fat cells simply get bigger (Hypertrophic adiposity). However, we now know that continued overeating will lead to new fat cells emerging even in late adulthood, and it is this new fat cell growth that is more difficult to counter.

Hope is now emerging for people that have always been overweight (people with excess fat cells). Just as we believed that once these new fat cells developed they were with you for life, it is now thought that if fat cells can be reduced to a certain size for a period longer than 9 months, they are programmed to die off. The significance of this finding is that hyperplasic adiposity is reversible, which was previously thought impossible. This is also why diets don’t work – they are too short-term and only shrink your fats cells, which simply leads to adiposity rebound – and you know what that means!

Set point theory suggests that following 9 months at a particular weight our bodies will re-set the “set point”, linked to the current number and size of fat cells. In other words, if you can lose weight and maintain it for at least 9 months, you have a good chance of long-term maintenance of the new lower weight. (Conversely if you are overweight for more than 9 months, this will become your new set point, and losing weight will be more difficult.) This is seen as the “ratcheting” effect of continual weight gain through life – or chronic hyperplasic adiposity.