Burn more calories with a low-carb diet, study suggests

19 Nov 2018 --- A new trial from Boston Children’s Hospital has linked low-carb diets to burning more calories and, subsequently, to successful and long-lasting weight loss. Significantly, the findings show that dietary composition may affect energy expenditure independently of body weight.

Following weight loss, energy expenditure decreases, metabolism slows down and the body burns fewer calories. This often leads to weight gain, though not much is known about how dietary composition influences this adaptive response over the long term. 

A new study led by Dr. Cara Ebbeling and Dr. David Ludwig compared the effects of diets varying in carbohydrate to fat ratio on energy expenditure over a twenty-week period. 

“Our study calls into question that all calories are created equal and suggests that lowering carbohydrate may increase calorie burning compared with lowering fat,” Dr. Ebbeling, Associate Director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital, tells NutritionInsight.

They monitored 234 overweight adults aged 18 to 65 years with a body mass index (BMI) of 25 or higher, who took part in an initial weight loss diet for about ten weeks. 

In total, 164 of test subjects reached the target weight loss of around ten percent of body weight and were then randomly assigned to follow either a high (sixty percent), moderate (forty percent) or low (twenty percent) carbohydrate diet for twenty weeks.

The participants were given fully prepared meals and the researchers tracked their weight and measured their energy expenditure to compare how the different groups burned calories at the same weight.

The results showed that over the 20 weeks, energy expenditure was significantly higher in participants who followed low-carb diets compared to those following high-carb diets. Participants on the low-carb diet burned 209 to 278 calories a day more than those on the high-carb diet. 

Those with the highest insulin secretion, within the low-carb diet group, at the beginning of the study saw a difference in total energy expenditure up to 478 kilocalories a day more than those who followed the high-carb diet. This “would translate into an estimated ten kg weight loss after three years, assuming no change in calorie intake,” state Ebbeling and Ludwig.

Hormones involved in energy balance (ghrelin and leptin) changed in a potentially advantageous manner in participants assigned to the low-carbohydrate diet compared to those assigned to the high-carb diet.

Ebbeling and Ludwig note that there are study limitations and possibly factors that cannot be controlled. Yet despite all this “a low glycemic load, high-fat diet might facilitate weight loss maintenance beyond the conventional focus on restricting energy intake and encouraging physical activity,” they conclude and say more research is warranted.

“Our study provides a piece to a large puzzle. When addressing complex research questions, no single study provides all of the answers. Like all studies, ours has strengths and limitations. More research is needed to replicate the findings and explore mechanisms linking dietary composition to calorie burning,” continues Dr. Ebbeling

Nevertheless, Dr. Ebbeling adds that not all carbohydrates are “off limits” and “whole fruits, beans, and other unprocessed carbohydrates can be part of a healthful diet. On the other hand, consuming added sugar, white flour, and other sources of refined carbohydrate may make it hard to keep weight off. Reducing consumption of these products can have metabolic benefits.”

By Kristiana Lalou