The heavier ones tended to sit, while the lean ones were more restless and spent two more hours a day on their feet—standing or walking. The difference translated into 350 calories a day, enough for the heavy people to take off about 14 to 18 kilograms a year, if they would get moving. 

       The researchers believe the tendency to sit still or move around is biological, governed by genetically determined levels of brain chemicals. And that tendency influences weight—not the other way around, they say. 

        Plenty of experts have been advising people to find small, relatively painless ways to burn extra calories, like taking the stairs instead of the elevators and parking at the far end of the lot to make themselves walk a bit. As to why the usual weight loss remedies frequently fail, Dr. Levine said, it is because people have a hard time sticking with exercise programs and diets. He argues that the very number of diet books and weight-loss plans is proof that none of them work.