Theory vs. Practice: What Works for Weight Loss


If youve been following what experts have been saying about weight loss lately, you might be tempted to just throw up your hands and go shopping for a bigger clothes size. An expert consensus statement released by the American Society for Nutrition and the North American branch of the International Life Sciences Institute challenges much of what you probably think you know about dieting.

Reduce your intake by 3,500 calories while keeping your activity level the same and youll lose a pound, right? Not exactly, say the experts, writing in the American Journal of Clinical Nutrition. While the equation that 3,500 calories equal one pound is technically correct, the popular belief lacks any time frame: The impression is given that even a temporary intervention will therefore result in a permanent body weight change. Moreover, the relationship between calories eaten and calories burned is complex, so that changes to one can lead to profound changes in the other side of the equation.

OK, so your metabolism slows and thats why weight loss often plateaus, right? More likely, the experts say, weight loss levels off because of failure to comply with the diet.

At least it must be true, as we keep hearing these days, that small lifestyle changes can prevent or reduce obesity. Nope, not the case: Because the 3,500-calorie per pound rule has often been used to model the effects of such interventions, unrealistic predictions are frequently made about the likely weight-loss benefits of exercise and dietary interventions that make only minor adjustments to lifestyle.

Before you give up completely, however, listen to Tufts expert Susan B. Roberts, PhD, who was one of the presenters at the symposium at which the consensus statement was developed. These are theoretical mathematical considerations, not a review of what works for weight loss, says Roberts, director of Tufts HNRCA Energy Metabolism Laboratory and author of The I Diet ( I would personally not give up on weight control, because we see it working all the time-and, after all, the paper in questions was a very theoretical analysis.

More useful for people looking to lose weight, Roberts says, is a study published about the same time in the American Journal of Preventive Nutrition-whose findings seem at odds with that expert consensus. These scientists looked at data on 4,021 obese adults from the National Health and Nutrition Examination Survey, 63% of whom had tried to lose weight in the previous 12 months. That percentage is in line with other studies that have found between 50% and 70% of the US population is working to shed pounds at any given time.

A surprising 41% succeeded in losing 5% of their body weight, while an additional 20% took off 10% of their body weight. That 10% weight loss is in line with National Institutes of Health recommendations for obese individuals to improve overall health.

Jacinda M. Nicklas, MD, MPH, MA, and colleagues at Beth Israel Deaconess Medical Center in Boston looked at what worked and what didnt for those looking to lose weight. Obese adults were more likely to achieve meaningful weight loss if they ate less fat, exercised more, used prescription weight-loss medications or participated in commercial weight-loss programs, they concluded.

On the other hand, Dr. Nicklas and colleagues found, Liquid diets, non-prescription diet pills and popular diets had no association with successful weight loss. And those who reported losing [at least] 10% body weight were less likely to report eating diet foods/products.

Tufts Roberts cautions that the study relied on self-reported data, and that the claim that 20% lost at least 10% of body weight should be taken with a grain of salt. Nonetheless, she says, It emphasizes that dietary change and exercise were better predictors of weight loss than fad diets or diet pills, which is a nice message!

TO LEARN MORE: American Journal of Clinical Nutrition, April 2012, American Journal of Preventive Medicine, May 2012; abstract at


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