There are people who seem to eat as much as they like, and don't seem to gain anything. Part of it is in the genes, and part of it is in the way the body seems to function.
Another part of it, according to the journal Science, is the fact that these people seem to get lots of exercise, whether they know it or not.
The secret, according to the Mayo Clinic, is NEAT, which stands for "non-exercise activity thermogenesis." The people who can ingest all those extra calories actually do burn it off. But instead of obvious exercise, they do it by fidgeting, changing position and lots of little motions that wind up using a lot of extra calories over the course of a day. - (HealthDayNews)