Maintaining weight loss with a diet that places heavy restriction on carbohydrates may allow dieters to eat more, in terms of total caloric value, a recent study suggests.
 
A study published in the Journal of Nutrition concluded that the dietary energy requirement, measured by calories, is higher for those on a low-carbohydrate diet than it is for those who consume higher portions of carbohydrates.
 
“If reproducible and generalizable, this finding may inform the scientific understanding of how dietary composition affects metabolism and the design of more efficacious long-term obesity treatment,” the authors said. “Pharmaceutical agents to increase energy expenditure, or to prevent the fall in energy expenditure following weight loss for obesity treatments have been sought for decades. Our study suggests that a low carbohydrate diet may produce this metabolic effect, without the risks of chronic drug treatment.”
 
According to the authors of the study, previous trials which reached the same conclusion had their validity questioned due to the fact that the methodology involved the doubly labeled water technique, a technique which has been questioned in the past as an accurate measure of energy expenditure.
 
Previous studies reported little effect of carbohydrate-to-fat ratios on total energy expenditure, however, these studies had a median duration of about one week, the authors of this study said. “The adaptation to a low-carbohydrate diet takes two to three weeks, limiting inferences about chronic macronutrient effects that can be drawn from these very short trials,” the authors wrote.
 
Rather than relying upon the doubly labeled water technique, researchers relied upon secondary outcomes, such as adiposity, in order to solidify their findings. A pool of 164 adults attained a mean run-in weight loss of 10.5%, and were randomly assigned diets that placed certain percentages on carbohydrate and fat intake, while protein remained controlled, in terms of caloric energy. Participants were required to adhere to a low-carb (20%/60%/20%), moderate-carb (40%/40%/20%), or high-carb (60%/20%/20%) test diet for a period spanning 20 weeks.
 
Calorie content was adjusted to maintain individual bodyweight within 2 kg of the post weight-loss value. Throughout the 20 weeks in which participants maintained their weights, following the 10.5% reduction, the estimated energy requirements of each participant from week 10 to week 20 was tested using ANCOVA (Analysis of Covariance), a measurement model which considers one independent variable at a time without the influence of others.
 
The mean EER (estimated energy requirement) was higher on a low-carbohydrate diet than a high-carbohydrate diet during weight loss maintenance in the participating adults, and remained significant in sensitivity analyses which accounted for change in adiposity, and possible non-adherence to the diet plans. The authors of the study estimate that the energy requirements for those on a low-carb diet compared to a high-carb diet are about 200-300 calories daily, which translates to roughly 50 calories/day for every 10% decrease in carbohydrate as a proportion of total energy.
 
Researchers concluded that the energy requirements exhibited during the study were commensurate with previous studies which used other methods of measuring total energy expenditure, including the doubly labeled water technique. “These data are consistent with the carbohydrate-insulin model and lend qualified support for the validity of the DLW method with diets varying in macronutrient consumption,” the authors concluded.
 
The authors of the study said that future research on the topic should include variables in energy expenditure, such as spontaneous physical activity (which was marginally higher in the low-carbohydrate diet), sleeping energy expenditure, nutrient cycling, and better access to metabolic fuels in the late postprandial state.