Long-term effectiveness of low-carb versus low-fat diets

For years, researchers have tried to determine which of two diets is safer and more effective for weight loss in the long run: the low-carbohydrate, Atkins-style diet, or the low-fat diet. Now, a new Temple University-led study has found that either diet works equally well when coupled with a comprehensive, behavioural support program.

The two-year study, published in the 3 August issue of the Annals of Internal Medicine, was the largest of its kind, and followed the weight loss of more than 300 people. Half were assigned to a low-carb diet, similar to the Atkins diet, and the other half were assigned to a low-fat, low-calorie diet. At the end of the study, participants in both groups had virtually identical weight loss.

But what set this study apart from others, aside from its length and size, was its behavioural treatment component, said Gary Foster, director of Temple’s Center for Obesity Research and Education and lead author of the study.

Each participant attended group sessions weekly for the first 20 weeks of the study, every other week for the next 20 weeks, and once every other month for the remainder of the study. In each session, participants discussed topics such as goal setting, self-monitoring, and limiting triggers to overeating.

"When comparing these two popular weight loss plans, none of the existing research had included a comprehensive, long-term, behavioural support component," said Foster. "This research tells us that people wanting to manage their weight need to be less concerned with which diet they choose, and more concerned with incorporating behavioural changes into their plan."

In addition to weight, researchers looked at levels of cholesterol, blood pressure, bone mineral density and percent of body fat. For both groups, each of these areas changed almost identically, except that in the low-carb group, levels of HDL cholesterol – the body’s "good" cholesterol – were higher than in the low-fat group.

"For years, the conventional wisdom was that low-carb diets had a host of ill effects on health, but these results suggest that those concerns are unfounded," said Foster.

(Source: Temple University: Annals of Internal Medicine)