A new study provides further evidence that diets with a higher proportion of protein might offer a metabolic advantage compared to a diet consisting of the same number of calories, but with a lower proportion of protein.

Edmonton study figure

Another popular weight management strategy is high-protein diets, which have been shown to promote weight loss and weight maintenance by increasing our sense of fullness, energy expenditure, and ability to maintain or increase fat-free mass.

In their study, the authors compared the impact of a high-protein total diet replacement to that of a control diet, a typical North American diet, on selected components of energy metabolism.

Lead author, Camila Oliveira, a doctoral student at the University of Alberta, noted, “Considering the prevalence of obesity worldwide and its impact on health, it’s not surprising nutritional strategies such as total diet replacements and high-protein diets are becoming increasingly popular as weight management strategies; however, research around these topics has not kept pace with their growth in popularity.”

In order to conduct their experiment, the authors recruited a group of healthy, normal-weight adults between the ages of 18 and 35 via advertisements placed on notice boards at the University of Alberta, Canada.

Subjects were then randomly assigned into one of two groups: one group was fed Almased, a high-protein total diet replacement which consisted of 35% carbohydrate, 40% protein, and 25% fat. The second group, the control group, was fed a diet with the same number of calories, but consisting of 55% carbohydrate, 15% protein, and 30% fat, a typical North American dietary pattern. Participants received the prescribed diets for a 32-hour period while inside a metabolic chamber.

Compared to the standard North American dietary pattern, the findings of this inpatient metabolic balance study revealed that those who took Almased experienced “higher energy expenditure, increased fat oxidation, and negative fat balance.”

In particular, the results of the study provide further evidence that a calorie is not just a calorie. That is, a diet with a higher proportion of protein might lead to an increase in energy expenditure and fat oxidation compared to a diet consisting of the same number of calories, but with a lower proportion of protein as well as a higher proportion of carbohydrate or fat.

Dr. Carla Prado, Professor, University of Alberta and the study’s principal investigator, commented, “Although these results are restricted to a specific population of healthy, normal-weight adults, they can help nutrition scientists and healthcare providers better understand the real physiological effects of a high-protein total diet replacement in humans. In our opinion, it is imperative to first understand the physiological impact of a high-protein total diet replacement [Almased] in a healthy population group so that the effects are better translated in individuals with obesity and its related comorbidities.”

“In summary, the results of this study suggest that high-protein total diet replacements may be a promising nutritional strategy to combat rising rates of obesity. Lead author Camila Oliveira added, “Future studies are needed to better understand the long-term effects of this dietary intervention on the physiology of both healthy and diseased population groups.”

Oliveira CLP, Boulé NG, Sharma AM, Elliott SA, Siervo M, Ghosh S, Berg A, Prado CM. A high-protein total diet replacement increases energy expenditure and leads to negative fat balance in healthy, normal-weight adults. American Journal of Clinical Nutrition. 2021 Feb 2;113(2):476-487. doi: 10.1093/ajcn/nqaa283.

About the Journal

The American Journal of Clinical Nutrition (AJCN) is the most highly rated peer-reviewed, primary research journal in nutrition and dietetics. AJCN publishes the latest research on topics in nutrition, such as obesity, vitamins and minerals, nutrition and disease, and energy metabolism. The AJCN was also selected by the Special Libraries Association (SLA) as one of the top 100 most influential journals in Biology and Medicine over the last 100 years.