Is it true that the maxim "eat less and exercise more" will help pretty much anyone lose weight? Is it physically harder for some people than for others? What does it mean for a human to have "a high metabolism"? The term is associated in my mind with people who can eat lots of calories without gaining weight. The implication seems to be that such a person burns more calories for the same activity level than others do. Why would this be the case? Is their resting core temperature higher? Are their muscles less efficient? Is it possible that their intestines simply absorb fewer of the calories in the first place, letting the rest pass through? Would that be the assumption under Occam's Razor?