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Weight loss is not that simple: Cutting 500 calories a day doesn't equal a pound lost per week
Medpage Today
Common rules of thumb exaggerate how much weight people will lose from a given dietary calorie reduction, leading to unrealistic expectations and disappointment, researchers said.
Whereas patients are often told that cutting 500 calories a day will let them lose a pound a week, a more realistic formula is that such a caloric reduction would lead to a 50-pound loss over three or more years, according to Kevin D. Hall, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, MD, and colleagues.
Even then, they explained in the Aug. 27 issue of The Lancet — a special edition devoted to obesity — such weight loss is possible only if the calorie reduction is actually maintained over that time.
The standard rules — endorsed by the National Institutes of Health and the American Dietetic Association, among others — fail to consider that human metabolism responds dynamically to changes in diet and body composition, Hall and colleagues asserted.
If a 300-pound dieter could really lose a pound a week by cutting his regular diet by 500 calories, he would vanish entirely in six years.
“This ubiquitous weight-loss rule (also known as the 3,500 [calorie]-per-pound rule) was derived by estimation of the energy content of weight lost, but it ignores dynamic physiological adaptations to altered body weight that lead to changes of both the resting metabolic rate as well as the energy cost of physical activity,” the researchers wrote.
