Friday Favorites: The 3,500 Calorie per Pound Rule Is Wrong

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The first surgical attempt at body sculpting was in 1921, with a dancer wanting to improve the shape of her ankles. The surgeon apparently scraped away too much tissue and tied the stitches too tight, resulting in necrosis, amputation, and the first recorded malpractice suit in the history of plastic surgery. Today’s liposuction is much safer…only killing about 1 in 5,000 patients, mostly from unknown causes; throwing a clot off into your lung, or perforations of your internal organs.

Liposuction currently reigns as the most popular cosmetic surgery in the world, and its effects are, indeed, only cosmetic. A study published in the New England Journal of Medicine assessed obese women before and after having about 20 pounds of fat sucked out of their bodies, resulting in nearly a 20 percent drop in their total body fat. Normally, lose even just 5 to10 percent of your body weight in fat, and you get significant improvements in blood pressure, blood sugars, inflammation, cholesterol, and triglycerides but, liposuction sucks. None of those benefits materialized even after the massive liposuction. This suggests subcutaneous fat—the fat under our skin—is not the problem. The metabolic insults of obesity arise from the visceral fat: the fat surrounding or even infiltrating our internal organs, like the fat marbling our muscles and liver. The way you lose that fat, the dangerous fat, is to take in fewer calories than you burn.

Anyone who’s seen The Biggest Loser shows knows with enough calorie restriction and exercise hundreds of pounds can be lost. Similarly, there are cases in the medical literature of what some refer to as “super obesity,” in which individuals lost up to 374 pounds largely on their own, without professional help, and kept it off for years. The guy lost about 20 pounds a month cycling two hours a day and reducing intake to 800 calories a day, which is down around what some prisoners were getting at concentration camps in World War II.

Perhaps America’s most celebrated TV weight loss was when Oprah pulled out a wagon full of fat, representing the 67 pounds she lost on a very low-calorie diet. How many calories did she have to cut to achieve that within four months? Consult leading nutrition textbooks, or refer to trusted authorities like the Mayo Clinic, and you’ll learn the simple weight loss rule: one pound of fat is equal to 3,500 calories. Quoting from the Journal of the American Medical Association, “A total of 3500 calories equals 1 pound of body weight. This means if you decrease your intake by 500 calories daily, you will lose 1 pound per week. (500 calories per day × 7 days = 3500 calories.)” The simple weight loss rule that’s simply not true.

The 3,500-calorie rule can be traced back to a paper in 1958 that just noted that since fatty tissue on the human body is 87 percent fat, a pound of body fat would have about 395 grams of pure fat. Multiply that by nine calories per gram of fat gives you that “3,500 calories per pound” approximation. The fatal flaw that leads to “dramatically exaggerated” weight-loss predictions is that the 3,500 rule fails to take into account the fact that changes in the calories-in side of the energy-balance equation automatically lead to changes in calories out—for example, the slowing of metabolic rate that accompanies weight loss, known as metabolic adaptation. That’s one of the reasons weight loss plateaus.

For example, imagine a 30-year-old sedentary woman of average height who weighs 150 pounds. According to the 3,500-calorie rule, if she cuts 500 calories out of her daily diet, she’d lose a pound a week, or 52 pounds a year. In three years, then, she would vanish. She’d go from 150 pounds to negative 6. Obviously, that doesn’t happen. What would happen is that in the first year, instead of losing 52 pounds she’d likely only lose 32 pounds, and then, after a total of three years, stabilize at about 100 pounds. This is because it takes fewer calories to exist as a thin person.

Part of it is simple mechanics, in the same way a Hummer requires more fuel than a compact car. Think how much more effort it would take to just get out of a chair, walk across the room, or climb a few stairs carrying a 50-pound backpack. That’s no lighter than carrying 50 pounds in the front. Even when you’re lying at rest sound asleep, there’s simply less of your body to maintain as we lose weight. Every pound of fat tissue lost may mean one less mile of blood vessels your body has to pump blood through every minute. So, the basic upkeep and movement of thinner bodies takes fewer calories. So, as you lose weight by eating less, you end up needing less. That’s what the 3,500-calorie rule doesn’t take into account.

Or imagine it the other way. A two-hundred-pound-man starts eating 500 more calories a day. That’s like a large soda or two doughnuts. According to the 3,500-calorie rule, in 10 years he’d weigh more than 700 pounds! That doesn’t happen, because the heavier he is, the more calories he burns just existing. If you’re a hundred pounds overweight, that’s like the skinny person inside you trying to walk around balancing 13 gallons of oil at all times, or lugging around a sack containing four hundred sticks of butter wherever you go. It takes about two doughnuts worth of extra energy just to live at 250 pounds, and so that’s where he’d plateau out if he kept it up. So, weight gain or weight loss, given a certain calorie excess or deficit, is a curve that flattens out over time, rather than a straight line up or down.

Nevertheless, the 3,500-calorie rule continues to crop up, even in obesity journals. Public health researchers used it to calculate how many pounds children might lose every year if, for example, fast food kids’ meals swapped in apple slices instead of French fries. They figured two meals a week could add up to about four pounds a year. The actual difference, National Restaurant Association-funded researchers were no doubt delighted to point out, would probably add less than half a pound—10 times less than the 3,500-calorie rule would predict. The original article was subsequently retracted.

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