Traditionally, nutritionists and researchers have assumed that all you need to do to lose weight is cut calories – about 500 calories per day to lose a pound per week for most dieters, from the assumption that each pound of weight lost represented 3,500 calories in reduced calorie intake or increased exercise.
“People have used this rule of thumb for decades, and it turns out to be completely wrong,” Kevin Hall, a scientist with the National Institutes of Health, said at the American Association for the Advancement of Science annual meeting in Vancouver.
Hall [a contributor to the National Collaborative on Childhood Obesity Research via the Envision project] said the reality is that losing weight slows a person’s metabolism, and the mathematical model typically used doesn’t take this slowing into account. When dieters report a “yo-yo” sequence, of weight loss, reaching a plateau in weight and then slowly regaining previously lost pounds, this is part of the reason.
New models may have some of the answers. The science of weight loss isn’t new; scientists have been struggling to understand it for almost 40 years, said Carson Chow, a senior investigator at the National Institutes of Health in Bethesda, Md., who is also an NCCOR Envision contributor. Chow said that what’s different now is that scientists are compiling many data sets into a single model.
Hall and Chow are part of a team that has created a new model, and an online weight simulation tool that shows what happens when people of varying weights, diets and exercise habits try to change their weight. Their model was first published last fall in the journal The Lancet.