The telegraph

How to tell if you have a faulty appetite gene

Imagine if there was a weight trigger that made you pile on the pounds – on average two and a half stones heavier than usual. Sometimes a lot more. Now imagine that such a trigger exists, but it is not greed or weakness. Instead, it’s a gene, a strip of chemical coding in our DNA, that is revolutionizing how some people perceive food while leaving others untouched. Would that make you look at obesity differently? Or are you even rethinking what is within and beyond individual human control? These are the fundamental questions the research published this week raises. A team from Cambridge University found that mutations in a single gene called MC4R can disrupt the brain’s perception of food and satiety. MC4R stands for Melanocortin-4 Receptor; Melanocortin is an important part of the critical system the body uses to recognize and determine fat reserves. “The job of MC4R is to tell you to stop eating after a meal,” says Sadaf Farooqi, professor of metabolism and medicine at Addenbrooke’s Hospital. “If it doesn’t work, you won’t get this signal.” The effects of a defective MC4R on fat mass and weight are, according to the paper notes, detectable as early as five years of age. When carriers of the same defective gene reach 18, they are 18 kg heavier than those with a functioning MC4R. “MC4R is the volume control,” says Farooqi. “When it doesn’t work, people gain weight even partially; If it doesn’t fully work, people put on a lot. ”Some of its effects, Farooqi says, is how efficiently the body burns calories. But most of its impact is perception. “First and foremost, it’s about how much you want to eat.” Giles Yeo, also the author of the paper, is like a pilot with a broken altimeter. The pilot thinks and reacts as if he is normally sailing at 30,000 feet when in fact he is dangerously close to the ground. So the person with the dysfunctional MC4R thinks they need to eat more and feels hungry when in fact their body no longer needs food. “We all have these moments when you’re hungry and wander downstairs to stare in the fridge,” he says. “It’s that level of hunger.” Except all the time.