SCIENCE: A Genetic Component to Obesity? “The mice were eating their usual chow and exercising normally, but they were getting fat anyway. The reason: researchers had deleted a gene that acts in the brain and controls how quickly calories are burned. Even though they were consuming exactly the same number of calories as lean mice, they were gaining weight. So far, only one person — a severely obese child — has been found to have a disabling mutation in the same gene. But the discovery of the same effect in mice and in the child — a finding published Wednesday in the journal Science — may help explain why some people put on weight easily while others eat all they want and seem never to gain an ounce. It may also offer clues to a puzzle in the field of obesity: Why do studies find that people gain different amounts of weight while overeating by the same amount?”

UPDATE: Reader Mitzi Perdue emails: “As someone in animal agriculture, I’ve always been puzzled that human geneticists don’t seem to know what virtually all cattle or poultry geneticists know: that you can breed for efficient feed conversion. Translated into English, that means animals can be bred to gain weight on fewer calories. In the animal agriculture world, this concept has been around for 35 years that I know of, and probably much longer than that.”