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Obesity – is it all in the genes?

Many obese people claim their size comes down to their genes. There does seem to be a slice of truth in this assumption. But, the evidence suggests it can certainly be challenged.

Research into the genes involved in obesity is very much still in its infancy. Nevertheless, the men and women in white coats do repeatedly talk about something called an ‘FTO’ gene, or ‘fat gene’ which they believe affects one in six people. Research published in the Journal of Clinical Investigation found that those carrying this strong variant of the FTO gene are 70 per cent more likely to become obese.

The study, led by scientists at UCL, the Medical Research Council (MRC) and King’s College London Institute of Psychiatry, found they tended to have higher levels of the hunger hormone, ghrelin, in their blood. This meant experienced considerably more hunger than a control group. They also craved more calorific food, even if they weren’t obese.

Brain scans also suggest that a particular set of FTO carriers have a stronger reaction to pictures of high-calorie food than their peers.

Dr Giles Yeo, is a scientist based at Cambridge University, who specialises in genes and obesity and has featured in various BBC Horizon shows on the subject. He number crunches even more specifically about the FTO gene. “If you have two ‘risk copies’ you are on average 3kg heavier (6.6Ibs) and 50% more likely to be obese; one copy (means) 1.5kg heavier  (3.3Ibs) and 25% more likely to be obese.”

In a fat-shaming society, Dr Yeo is often slammed for claiming some people are simply more hard wired to eat more. Appearing on The Andrew Marr Show on Sunday 5 June, he admitted: “Every time I say I’m a geneticist it’s not a problem; when I say I study the genetics of obese people I become the “Fat Guy” – a bad fat guy because I’m giving fat people an excuse.

In a self-penned newspaper article published today (7 June), Dr Yeo stresses: “Let’s be clear – the increase in obesity over the past 30 years has, undeniably, been down to changes in lifestyle and food availability. Put simply, we eat too much and move too little. It is physics. Gene research shows, however, that some people eat more than others because they feel a little more hungry all of the time. Thin people, therefore, are not morally superior beings able to say ‘no’ to temptation; they just feel less hungry.”

Drug companies are now ambitiously working on hormonal treatments which trick the brain into thinking the stomach is full. Of course, what these treatments don’t account for is the fact that just as the alcoholic doesn’t drink  because they’re thirsty, few obese people overeat because they’re physically hungry. Instead, they hunger for escape and comfort.

Furthermore, before anyone admits genetic defeat and reaches for the wine and crackers, it’s important to note many people with ‘fat genes’ remain slim and healthy. So, what’s their secret?

Dr Dean Onrush, a Clinic Professor at the University of San Francisco and his colleagues recently demonstrated that up to 500 genes change their behaviour when a person alters their diet, stress-management skills and activity levels. Even conditions such as heart disease, cancer and diabetes that have been passed through family generations can be prevented. Furthermore, fat genes alone simply cannot account for the huge explosion in obesity over the last 30 years, which has seen obesity rates triple among adults.

Dr Bruce Lipton, an American stem-cell biologist, blasts the notions of people’s genes being set in stone. “The notion that our fat is indelibly inscribed in our genes was directly derived from the now outdated scientific concept known as genetic determinism, which would have us believe that we are victims of genetic forces outside of our control,” he says. “Unfortunately, the assumptions of powerlessness are a one-way street to personal irresponsibility. Too many of us have said: “Hey, I can’t do anything about it anyway, so why should I care? Overweight? It runs in my family. Pass me the bonbons.” 

HORIZON: Why Are We Getting So Fat?, BBC2, 9pm, tonight.