Some scientists and doctors began speculating that healthy people who were sporting extra pounds didn’t necessarily need to worry about losing weight. As one researcher told a reporter in 2004, ‘If a fat person or obese person has normal blood pressure, if their total cholesterol and glucose levels are normal and they are healthy, there is no reason they should necessarily have to lose weight.’ ‘The fit or fat issue has unbelievable levels of complexity,’ says Tim Church, M.D., Ph.D., the director of Preventive Medicine Research at the Pennington Biomedical Research Center in Baton Rouge, La. Perhaps being active affects how fat cells operate in a heavy person. Age plays a role, too, he says, as do genetics. The very categorization of fatness using B.M.I. is a gross oversimplification, he adds.