Scientists have identified a genetic master-switch that makes some people more prone to obesity than others, and research out Wednesday suggests it can be turned off, possibly leading to weight loss. If future studies are successful, the method could offer a novel way to cure obesity, a major public health problem that experts say affects some 500 million people around the world and can lead to cardiovascular disease, Type 2 diabetes and cancer. “Obesity has traditionally been seen as the result of an imbalance between the amount of food we eat and how much we exercise, but this view ignores the contribution of genetics to each individual’s metabolism,” said senior author Manolis Kellis, a professor of computer science at the Massachusetts Institute of Technology (MIT).