New investigations into obesity may identify people with an inherited risk of weight gain, explain why crash diets often fail and address a danger period in childhood that leads to obesity in adult life. Sifting through the genetic codes of 77,000 people, a British-led international team say they have found culprit variants in DNA near a gene already fingered in the molecular ballet that causes obesity. The gene, called MC4R, orchestrates appetite and energy expenditure.