Defeating obesity is rarely easy. For many people, even successful weight loss is followed by a prolonged struggle to prevent the weight from coming back . Obesity relapse is common, and research indicates it's more than a matter of willpower. Fat cells retain a 'memory' of obesity long after weight loss, studies have found, potentially undermining efforts to avoid regaining weight. And it's not just fat cells. As researchers report in a new decade-long study, certain immune cells can also