There has long been debate about the relative merits of a low-carbohydrate diet, as popularised by Atkins, compared to the more traditional low-fat approach to weight loss. A low-carbohydrate diet has also been anecdotally associated with adverse effects on health.
A newly published clinical study, led by researchers at the Center for Obesity Research and Education at Temple University, Philadelphia, has now shown remarkably little difference between the two regimes. The study followed over 300 subjects randomly assigned to either diet over a two year period and, importantly, combined the diets with comprehensive behavioural treatment.
In the low-carb group, carbohydrate intake was limited to 20 g/d for 3 months in the form of low–glycemic index vegetables with unrestricted consumption of fat and protein. After 3 months, participants were allowed to increase their carbohydrate intake (5 g/d per wk) until a stable and desired weight was achieved. The low-fat diet consisted of limited energy intake (1200 to 1800 kcal/d) with less than 30% of the calories derived from fat. For the behavioural treatment, 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.
Although attrition was high at 2 years, there were no differences in weight, body composition, or bone mineral density between the groups at any time point. Weight loss was approximately 11 kg (11%) at 1 year and 7 kg (7%) at 2 years. The low-carbohydrate diet group had greater increases in high-density lipoprotein cholesterol (“good” cholesterol) levels at all time points, increasing by approximately 23% at 2 years, suggesting that a low-carb diet may have some cardiovascular benefit.
Gary Foster, Director of Temple’s Center for Obesity Research and Education and lead author of the study said:
When comparing these two popular weight loss plans, none of the existing research had included a comprehensive, long-term, behavioural support component. 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.
The study is published in Annals of Internal Medicine.