I just finished watching a BBC Horizon documentary called “Why Are Thin People Not Fat?”  It was a lot more interesting than I had expected and changed some of my beliefs about obesity and body weight.

The documentary covers an experiment where they take 10 slim people and have them eat double their normal calories for 4 weeks.  The aim was to track how people put on weight and how much of that weight was body fat.  As expected, some people gained more weight than others. For some, a higher percentage of that extra weight consisted of body fat. Other people hardly put on any noticeable weight.  One guy increased his weight by about 8% but it was mainly muscle!  Seems that he has a gene where excess calories are used to build muscle mass instead of being stored as fat. How lucky is that guy!?  Other things I learned:

• There is a virus, first discovered in chicken, that grows itself in fat tissue and at the same times grows more fat cells.  It has been shown that obese people are three times more likely to be carriers of this virus.
• Once a fat cell reaches a certain size, and your fat cells can’t grow any bigger, your body will make more fat cells. Once you have a fat cell, it is almost impossible to lose it. You can only decrease the size of it.  Conclusion: If you get really fat, your body will reach a  point where it makes more fat cells, and even when you get thinner, you’ll retain that increased number of fat cells.
• There may be a genetic component to what is your natural weight. Your body could be programmed to be at a weight that is overweight and obese, even if you lose the weight, your body will feel uneasy and hungry as it strives to get back to what it considers its natural weight.
• An experiment with children showed that from an early age, some of us naturally stop eating when we’re full. Others do not.  There may be a mechanism beyond our control that dictates how food affects us.

I highly recommend you watch the video yourself on YouTube.  It’s broken down into 7 parts but you can watch it all at once by clicking Play All Videos.

Why Are Thin People Not Fat? [YouTube Playlist]

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