Abstract
The latest battle in the perpetual diet wars has claimed that low carbohydrate diets offer a metabolic advantage to burn more calories and thereby help patients maintain lost weight.
However, analyzing the data according to the original pre-registered statistical plan resulted in no statistically significant effects of diet composition on energy expenditure.
The large reported diet effects on energy expenditure were calculated using the revised analysis plan that depended on data from subjects with excessive amounts of unaccounted energy. Adjusting the data to be commensurate with energy conservation resulted in a diet effect on energy expenditure that was only one third of the value reported in the BMJ paper.
Diet adherence is key to sustained weight loss, and no diet has yet demonstrated a clinically meaningful superiority for long-term maintenance of lost weight. More research is required to better understand the factors that sustain healthful diet changes over the long-term.
Proponents of low carbohydrate diets have long claimed that such diets cause greater calorie expenditure thereby providing patients with a “high calorie way to stay thin forever”1. Indeed, a substantial persistent increase in total energy expenditure (TEE) with a low carbohydrate diet could be an important advantage given that long-term maintenance of lost weight remains the most vexing clinical challenge in the treatment of obesity2. While most studies have found no clinically meaningful effect of the dietary carbohydrate to fat ratio on TEE3, a recent randomized controlled trial by Ebbeling et al. reported substantial TEE differences between low and high carbohydrate diets during maintenance of lost weight4. But the data may not support this conclusion.
