New obesity research revises the weight loss assumptions

Posted by AFN Staff Writers on 26th August 2011

New research on obesity, published today by the world-renowned medical journal The Lancet, has revealed that, for decades, dietitians and doctors have been basing weight-loss advice on mistaken assumptions.

The results of one study reveal how most weight-loss programs have overemphasized the importance that energy intake has on weight-loss.

A research team led by Kevin D. Hall, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases in Maryland, USA, found that whereas patients are often advised that cutting 500 calories a day will allow them to lose one pound a week, the reduction for a 50-pound loss of weight would require three or more years, rather than 12 months.

Dr Hall said, “Health and nutrition organisations have perpetuated the myth that a reduction of food intake of 2 MJ per day will lead to a steady rate of weight loss of 1.1 pounds per week. Because this weight-loss rule does not account for dynamic physiological adaptations that occur with decreased bodyweight, its widespread use at both the individual and population levels has led to drastically overestimated expectations for weight loss.

“Body weight response to a change of energy intake is slow. Furthermore, adults with greater adiposity have a larger expected weight loss for the same change of energy intake, and to reach their steady-state weight will take longer than it would for those with less initial body fat.

“On the basis of our model, we propose an approximate rule of thumb for an average overweight adult: every change of energy intake of 100 kJ per day will lead to an eventual body weight change of about 1 kg (equivalently, 10 kcal per day per pound of weight change) with half of the weight change being achieved in about one year and 95% of the weight change in about three years.

“Accurate mathematical models of human metabolism are needed to properly assess the quantitative effect of interventions at both the individual and population levels. Widespread past use of erroneous rules for estimation of human weight change have led to unrealistic expectations about the potential effect of both behavioural and policy interventions.”