Two new studies show underlying biological differences between obese people and thinner folks — obesity may be linked to a gene that affects appetite, and, more surprisingly, to a person's sense of smell.
According to one study, reported in the Daily Mail, a gene called FTO could have a major influence on obesity. People with two "rogue" copies of the gene had a 70% greater chance of obesity than average — and a 50% greater risk of diabetes. And those with just one copy of the gene variant were 30% more likely to be obese and 25% more likely to get diabetes. FTO appears to influence appetite, but scientists aren't sure how. Says researcher Chris Church,
For the first time we have provided convincing proof that the FTO gene causes obesity. The next step is to understand how it does this, for instance whether it increases appetite by influencing our brain or alters messages from our fat stores and other tissues.
The other study, reported by the BBC, found differences in the way overweight and thin people smell food. Overweight subjects tended to be better at picking up food smells than thinner people, especially if they'd just eaten. Study author Dr. Lorenzo Stafford says, "It could be speculated that for those with a propensity to gain weight, their higher sense of smell for food related odours might actually play a more active role in food intake." It makes a certain amount of sense — smell is intimately related to taste, and people who are better able to smell food might have greater appetites.
Of course, appetite is only part of why people gain and retain weight, and one thing that's interesting about weight research in general is how little we still understand. We know of a few genes and hormones that might influence how much people eat — maybe in part by influencing their senses. But we don't fully understand how these genes work, and we're nowhere close to controlling their action (the Daily Mail notes both the inefficacy of dieting and the failure of a spate of recent weight-loss drugs). So far, only a few things are certain: that the reasons we gain weight are complicated, and losing it is far from simple.