Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial (https://www.bmj.com/content/363/bmj.k4583)
See the link for the full article, but here's the discussion section:
In this controlled feeding trial over 20 weeks, we found that total energy expenditure was significantly greater in participants assigned to a low carbohydrate diet compared with high carbohydrate diet of similar protein content. In addition, pre-weight loss insulin secretion might modify individual response to this diet effect. Taken together with preliminary reports on activation of brain areas involved in food cravings48 and circulating metabolic fuel concentration,49 results of the current Framingham State Food Study (FS)2 substantiate several key predictions of the carbohydrate-insulin model. Regardless of the specific mechanisms involved, the study shows that dietary quality can affect energy expenditure independently of body weight, a phenomenon that could be key to obesity treatment, as recently reviewed.50
The difference in total energy expenditure was 209 to 278 kcal/d or about 50 to 70 kcal/d increase for every 10% decrease in the contribution of carbohydrate to total energy intake (1 kcal=4.18 kJ=0.00418 MJ). This effect is comparable to that obtained by isotopic methods over one month intervention periods in a previous randomized crossover study with 21 adults39 and in a non-randomized crossover study with 17 men,51 after taking into account confounding by ongoing weight loss and other sources of bias.5253 If this effect persisted—and we observed no attenuation from 10 to 20 weeks—it would translate into an estimated 10 kg weight loss after three years for a typical 30 year old man of height 178 cm, baseline weight 100 kg, and average activity level, assuming no change in energy intake (www.niddk.nih.gov/bwp). If reduction of glycemic load also decreased hunger and food intake,36 the long term benefits could be even greater.
The difference in total energy expenditure between low and high carbohydrate diets among those in the highest third of insulin secretion was more than double the difference for those with low insulin secretion, highlighting a subgroup who could do particularly well with restriction of total or high glycemic load carbohydrates. This finding is consistent with results from an animal study,54 a cohort study,55 mendelian randomization analysis,56 and clinical trials.303157 In contrast, the recent DIETFITS (Diet Intervention Examining The Factors Interacting with Treatment Success) trial reported no effect modification by insulin secretion or genetic factors among 609 overweight adults assigned to low fat compared with low carbohydrate diets for 12 months.58 In that study, however, which relied on nutrition education and behavioral counseling, participants were instructed to “minimize or eliminate refined grains and added sugars and maximize intake of vegetables” and other minimally processed foods. Probably for this reason, the reported glycemic load of the low fat diet was very low for a diet that is by nature higher in total carbohydrate, and similar to the value for the lowest glycemic load diets in some previous intervention studies.59Thus, the effects of predisposing risk factors might be attenuated on diets that are generally healthy and specifically low in glycemic load. In support of this possibility, a high genetic risk score for obesity predicted obesity among people consuming high glycemic load sugary beverages but not among non-consumers.60
Similar to our previous crossover study,39 the difference in total energy expenditure between diets was not primarily attributable to resting energy expenditure or physical activity level, which were marginally higher in participants assigned to the low carbohydrate diet (comparisons that could have been underpowered). Other potentially contributory components of energy expenditure include thermic effect of food, activity of brown adipose tissue, autonomic tone, nutrient cycling, fidgeting and related non-exercise activity thermogenesis,61 and changes in the efficiency of movement that we did not capture with cycle ergometry.45466263
A change in metabolism is suggested by hormonal responses to diet. Ghrelin, produced primarily in the stomach, was significantly lower in participants assigned to the low carbohydrate diet, a novel finding. Beyond effects on hunger, ghrelin has been reported to lower energy expenditure and promote fat deposition,6465 providing another mechanistic explanation for our primary outcome. Leptin (an adipocyte hormone that signals body energy stores) was also lower in participants assigned to the low carbohydrate diet, suggesting improvement in leptin sensitivity.66Prospective studies have observed that people with the greatest declines in leptin levels after weight loss have the lowest risk for weight regain.676869
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