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Study under review: Do Lower-Carbohydrate Diets Increase Total Energy Expenditure? An Updated and Reanalyzed Meta-Analysis of 29 Controlled-Feeding Studies
Weight loss is one of the most effective tools for lowering the risk of chronic diseases like diabetes and cardiovascular disease. Weight loss requires a calorie deficit over an extended period of time, which can occur via reduced calorie intake, increased energy expenditure, or both. It’s been hypothesized that the macronutrient distribution of a diet affects total energy expenditure, in that low-carbohydrate diets are successful partly due to their ability to increase the thermic effect of food and basal metabolic rate.
There have been several studies that have examined the effects of low-carbohydrate diets on total energy expenditure (TEE), as compared to high-carbohydrate diets. For example, one randomized controlled trial found that a low-carbohydrate diet containing 20% calories coming from carbs increased total energy expenditure by about 100–200 kcal per day. However, another randomized controlled trial found that a very high-carbohydrate diet led to an approximate 350 kcal per day increase in total energy expenditure, compared to a very low-carbohydrate diet. Furthermore, a previous 2017 meta-analysis of 28 studies found that a lower-carbohydrate diet reduced total energy expenditure by about 25 kcals per day. However, the trials in that meta-analysis had a median duration of about four days. Some have argued that there is a metabolic adaptation period to low-carbohydrate diets that takes several weeks, and the proposed increase in TEE only occurs after that adaptation period is complete.
To test this hypothesis, the authors of the present study conducted a meta-analysis to compare the effects of diets differing in carbohydrate content on TEE over shorter and longer periods of time.
Total energy expenditure is one of the primary components that determines weight loss. There has been speculation that differing macronutrient profiles may have meaningful effects on total energy expenditure, making some diets more effective for weight loss. Randomized trials have led to conflicting results on whether lower-carbohydrate or higher-carbohydrate diets are more effective for fat loss. Potential interactions with diet duration have not been considered in previous meta-analyses. The authors of the present study used a meta-analysis to compare the effects of diets differing in carbohydrate content on TEE over shorter and longer periods of time.
Other Articles in Issue #75 (January 2021)
Safety Spotlight: Women and creatine
The effects of creatine are quite well studied, but its sex-specific safety profile hasn't been. Besides some non-serious side effects, creatine seems safe for women, but more work needs to understand creatine's effects during pregnancy.
The effects of increased protein intake on overall energy intake in older adults
Boosting protein intake may help stave off the loss of muscle strength and function that can come with age. But does increasing protein affect energy intake in older adults as well? We cover a recent meta-analysis that explored this question.
Sugar Wars, Episode 6: The Return of the Fructose
How does fructose affect cardiometabolic risk markers calorie-for-calorie compared to glucose or sucrose? This recent meta-analysis aimed to find out.
Deep Dive: Supplementing for senior strength and size in the context of sarcopenia
This systematic review and meta-analysis explored what supplements can stave off the loss of muscle function that comes with aging. However, the way it categorized the studies it used, along with the overall low quality of those studies, makes its conclusions seem a bit... weak.
Interview: Cyriac Abby Philips, MBBS, MD, DM (Hepatology)
In this interview, we pick Dr. Philips' brain about the basics of Ayurveda, its safety, and the story behind a recently retracted paper he was involved with detailing a case of acute liver failure and death in a patient who was taking supplements.
Deep Dive: Comparing the efficacy of diet, exercise, and lifestyle modifications for controlling childhood obesity
This meta-analysis looked at what lifestyle interventions work best for children with overweight and obesity, and how much of a role parental involvement played.
Deep Dive: Evaluating the relationship between training status and optimal protein intake
According to this recent meta-analysis, whether or not more protein is better for lean body mass may come down to resistance training status.