THE HUNGER GAME

Obesity is on the rise, but as we blame our unhealthy food-ridden environment and look to wonder drugs to get rid of unwanted fat, what role do our genetics play?

- GILES YEO

Iam a geneticist, which, last time I checked, is a perfectly upstanding profession. I mean my mother-in-law still speaks to me, so that must be a good thing, right?

And yet, when I reveal that I study the genetics of body weight and that your genetics can be the driving cause of obesity, I become a bad person. I'm perceived as giving overweight or obese people terms I don't use in a pejorative fashion - an excuse.

This has always been an interesting take for me. If I were studying something else, like the genetics of cancer, dementia, arthritis or any other disease, would I suddenly be giving the people who are suffering from those conditions an excuse? I'd hope not. Instead, I hope that people would understand that I'm trying to understand biology and mechanisms, and, shocking I know, I might even be trying to help some of them.

IT'S IN THE GENES

When we talk about body weight, it's all too often considered to be a matter of lifestyle', a habit, a lack of willpower, a choice. The reality is that while rapid changes in our food environment and lifestyle have undoubtedly driven up the obesity figures worldwide, there are many people who are skinny and others who aren't. There's clearly a large variation in body weight, even in the 'obesogenic' environment we live in today (one that promotes weight gain). A large part of this, although by no means all, is down to genetics.

Much of the evidence for a genetic basis to body weight has come from the study of twins. There are identical twins (who are, for all intents and purposes, genetic clones of each other) and there are non-identical twins (who share as much genetic material as you would with your own siblings or parents - 50 per cent). If you study a large enough number of twin pairs, let's say thousands, then you can examine any given human trait or behaviour and compare the variation if 100 per cent of genes are shared versus 50 per cent.