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Fat facts

Fat facts the assumption - in force till a few years ago - that obesity, or the condition of being overweight, might be reduced by simple drug treatment, had been a cause for much euphoria. Recent studies, however, indicate that things may not be all that straightforward. It has long been known that people get fat either because they eat too much or because of a hereditary tendency to put on fat. Of course, they may eat too much because of a predisposition to do so, but the point is that there are also other, non-genetic explanations for overeating.

The relative importance of genetic factors in the determination of the level of body fat has long been under scrutiny. The idea that genetic defects might play a significant role in regulating body weight had gained strong support with the discovery of a gene named 'ob' (for obesity) in 1994. The protein product encoded by ob was named leptin (after leptos , the Greek word for thin).

The suggestion that ob might have something to do with the regulation of body weight arose from observations on mice that had defective copies of ob ; such mice lack leptin and tend to be markedly overweight. However, when injected daily with either mouse leptin or human leptin, their food intake is reduced and energy expenditure raised leading to a weight loss of as much as 30 per cent in two weeks.

It was hypothesised that leptin produced by the adipose tissue acted as an endocrine hormone, an internal signal to inform the hypothalamus

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