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Common dieting wisdom says that we'll lose one pound for every 3,500 calories we burn. Is that true?
The above quoted formula is taken as dieting orthodoxy: to lose one pound of fat per week, simply create a 3,500 calorie deficit through diet and exercise et voila, lose a pound a week for as long as you can keep it up.
If only it were that simple. Instead, the 3,500 fewer-calories-per-week strategy (what amounts to 500 fewer calories per day) is a good guideline to help create a calorie deficit, but that doesn't mean it will result in one pound lost every seven days.
The formula comes from a simple truth: there are 3,500 calories in a pound of human fat, explains Dr. Donald Hensrud, chair of preventive medicine at the Mayo Clinic and medical editor-in-chief of The Mayo Clinic Diet. But diet and exercise cause the body to lose lean tissue and water along with fat, making it unlikely that initial weight loss truly addresses fat only. What's more, individual metabolic rates vary based on genetics, fitness level and even size: for example, a heavier person also has more muscle mass and requires more calories. The 3,500 calorie deficit will simply have a more dramatic effect on them, explains Hensrud.
"If there is a calorie deficit, people will lose weight, no question. It’s not a bad starting point, but the rate of weight loss is complicated by a slowing down of metabolism to compensate for lack of food," agreed Marion Nestle, professor of nutrition at NYU in an email to Healthy Living. "Body fat is not pure fat -- it is mixed with proteins and water, thereby diluting the theoretical number (454 grams x 9 calories/gram)."
In fact, the initial stages of the diet are a time of rapid water weight loss. That's a good sign. As Hensrud explains, when we reduce our calorie consumption, particularly of carbohydrates, our body feeds off the store of glycogen in our muscle tissue and liver. Glycogen is a mixture of carbohydrate and mostly water. But just because initial weight loss is water weight loss doesn't mean the dieter is doing a bad job -- quite the contrary.
So if you aren't losing a pound of fat with that 3,500 deficit, what should you do to ensure steady weight loss? Hensrud recommends beginning with a small overall energy balance -- meaning, the daily total of calories should be low, even just 1,200 for a woman and 1,400 for a man, either from restrictive eating or increased physical activity and exercise. That's because, across the board, people generally underestimate their calories by 20 percent. So starting with lower-than-necessary calories will help keep dieters at a calorie deficit.
A lot of patients ask if increasing calorie expenditure through exercise is preferable to decreasing calories consumed, Hensrud explains. "What's interesting is that to keep weight off, the research shows that physical activity is more important for that phase," he says. "But to lose weight, calorie restriction is best."
Another important aspect of weight loss: adjusting expectations. Work to decrease calorie intake and to increase daily activity and exercise. But if you're doing all of those to the best of your ability, it may be time to readjust your idea of what weight loss looks like. "Sometimes success is just maintenance," Hensrud says.
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