Too Fat for Exercise?
Whether we like it or not, and most of us don’t, we cannot survive without body fat. It is our fuel reserve and a source of energy. It keeps us warm and helps protect our bones and organs from injury. But of course some of us are better cushioned than others.
Men, dietitians say, should have 12-24 per cent of their body tissue made of fat, whilst women should expect 15-30 per cent. There’s nothing much wrong with a little comfortable weight but you certainly can be made to feel like a pygmy hippo when it comes to looking for a pair of jeans or anything else you want wear.
Sometimes, it seems if you’re not built like a pipe cleaner with the girth of a herring, you are considered out of shape, out of date and out of the question. Let's look at a few relevant facts about fat, how it gets there, what it does, and maybe how to shift some of it.
Brown Fat and Yellow Fat
Our bulk contains two distinctly different types of body fat: brown, which is very active metabolically; and yellow, which stacks itself on in all the obvious places. The difference is that brown fat is ‘closest to the bone’, actually bound to the backbone, mainly concentrated in the neck and back to produce body heat.
It is called brown because of the high concentration of tiny chemical powerhouses called mitochondria and cytochromes, which are the scientific names for the parts of our cells that generate energy. They blaze away like tiny furnaces intent on rendering down and disposing of all those extra calories we seem to take in no matter how hard we try not to.
Yellow fat has none of these kilojoule-burning properties and really doesn’t do much except make us look and feel uncomfortable, getting in the way of effective exercise and increasing our chances of obesity, heart disease and other potential problems related to excessive weight.
As we grow older, our brown fat deposits seem to become less active along with the rest of us. Less active means less thermogenically responsive — it doesn’t burn kilojoules the way it used to. Instead of being burned off, those unwanted kilojoules are stored as excess fat. So, if you are a highly active, regular, dedicated exerciser you can even overeat and still stay slimmer than a non-exerciser who seems to gain a kilo by just watching a food commercial.