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 3,500 calories equals one pound of body weight. This means if you decrease your intake by 500 calories daily, you will lose one pound per week.”
But chew on this: This simple weight loss rule doesn’t add up.
The 3,500-calorie rule can be traced back to a paper in 1958 that noted that since fatty tissue on the human body is 87 per cent fat, a pound of body fat would have about 395 grams of pure fat. Multiply that by nine calories per gram of fat, which gives you the “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 the metabolic rate that accompanies weight loss, known as metabolic adaptation. That’s one of the reasons weight loss plateaus.
If you decrease your intake by 500 calories daily, you will lose one pound per week.
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 six. 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 function at a lower weight.
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. 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, basic upkeep and movement takes fewer calories. Essentially, 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. 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. 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.
To learn about the new rules on calculating what’s exactly in a pound, Click Here.
Excerpt republished with permission from Friday Favorites: The 3,500 Calorie per Pound Rule Is Wrong; Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0).
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