(FORTUNE Magazine) – The main conclusion of a recent report in The New England Journal of Medicine wasn't startling. The study, which tracked the health, weight, and habits of some 17,000 Harvard alumni age 35 to 74 over a 16-year period, found that those who exercised regularly but didn't overdo it had a greater life expectancy than their more sedentary fellows. But there was one real shocker. The researchers discovered that the men who had gained the least weight since graduation were dying off faster than those who had piled on the avoirdupois. They found that on average the alumni who had put on less than 15 pounds had a 30% higher death rate than their colleagues who had gained 25 pounds or more. The results rather baffled the researchers. They speculated that the death rate might be higher among the slimmer alumni because that group included many more cigarette smokers, as well as more victims of debilitating diseases. So the researchers did not recommend that anyone go out and pack on some lard in order to ensure longevity.