Have a favorite way to lose weight, one that has worked for you? As long as it involves cutting calories over the long term, then it will probably be effective. That’s the basic lesson from the latest research.
Last week Frank Sacks, a Harvard professor of nutrition, and his colleagues published a major study in the New England Journal of Medicine, Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein and Carbohydrates (full text). A total of 811 participants from Boston and Baton Rouge were divvied up into four diets with different emphases on protein and fat. The participants were then followed over two years. The conclusions, as summarized by Journal Watch, were:
Changes in weight and waist circumference at 6, 12, 18, and 24 months were indistinguishable among groups: At 2 years, only about 15% of each group had lost at least 10% of body weight. Attendance at group counseling sessions strongly predicted successful weight loss.
So there’s the catch! The weight loss was modest. As the Journal Watch title puts it, “Four low-calorie diets yield the same mediocre results. Dieters ate different amounts of protein, fat, and carbohydrate — but, after 2 years, most were still obese.” Still, many people would accept an average loss of 9 pounds and 2 inches less of waistline.
The main implication of this study is that calories matter, not diets. As Frank Sacks emphasized in a great interview on Science Friday, most research on diets has focused on the short-term. But weight loss is a long-term problem – and there calorie restriction is what really adds up. How to achieve that is a major issue, which I considered at length in a previous post on successful weight loss.
In the Science Friday interview Sacks himself ends up advocating a “very common sense approach – to have portion control, to cut out the highest calorie stuff you are eating, and getting some exercise. It’s all an integrated whole.” To that end, Sacks says that individuals should experiment with different diets to see what works for him or her.
On the research side, Sacks bluntly states that “we should move on from trying to figure out which diet is best.” Rather, we should examine why individuals vary so much in their response to weight loss programs. “The difference in individual response just overwhelms any possible dietary difference.”