Straight Talk on genetics and fat

I have nothing more to add to this except to claim heritage for my poor body shape and consequent body image issues.

By Caroline Bollinger
From the January 2009 Issue

Leave it to men to agree to stuff their face in the name of science! For 84 out of 100 days, a handful of male identical twins volunteered to consume an extra 1,000 calories per day for a study published in The New England Journal of Medicine. Theoretically, every guy should have gained the same amount—about 24 pounds—because it takes 3,500 additional calories to put on 1 pound. Instead, each twin gained about the same number of pounds as his twin, but there was a dramatic difference in gain between the twin sets. Some packed on as many as 29 pounds, whereas others saw the scale go up as little as 9.5 pounds. These findings and others have led scientists to estimate that at least 40 percent of our weight may be determined by the genetic cards we're dealt. Here are some potential players in being naturally slim:

Brown fat It sounds and looks gross (it's darker than the white fat we all know and loathe), but brown fat is desirable because it burns more calories. All babies are born with it—it helps generate body heat when we're young and vulnerable to cold—but it may disappear as we develop other ways to stay warm (like learning when to put on a sweater). But at least 8 percent of women keep some brown fat, usually in their neck and chest, says C. Ronald Kahn, M.D., vice chair of the Joslin Diabetes Center in Boston, who's researching brown fat's benefits: "It could be that deposits of brown fat protect some people against weight gain, because they force the body to burn more energy."

Gas-guzzling cells Fuel efficiency is a great quality in a car, but when it comes to your body, wasting energy is the way to go. The less energy you eke out of each calorie you consume, the more calories you burn just to survive. "In humans, caloric efficiency can vary by a couple of percentage points, and that's enough to make a difference in body weight," Ravussin says. An average 150-pound woman who uses only 2 percent less energy per day could store up to 5 extra pounds in a year.

Inner drive You can't turn regular fat into brown, but you can speed your body's rate of calorie burn by building more lean muscle mass with strength training and weight-bearing exercises such as hiking and dancing. Muscle is more metabolically active than white fat, meaning it burns more calories doing nothing. It also feeds off fatty acids released from fat cells, so as muscle builds, fat cells shrink (if you don't eat excess calories). Good trade!