Hypocaloric Low-Carbohydrate and Low-Fat Diets with Fixed Protein Lead to Similar Health Outcomes in Obese Mice

Objective: It is controversial whether low-carbohydrate diets are better suited for weight control and metabolic health than high-carbohydrate diets. This study examined whether these diets induce different improvements in body composition and glucose tolerance in obese mice during caloric restriction (CR).

Methods: Male C57BL/6J mice were fed an obesogenic diet ad libitum for 18 weeks and then subjected to 6-week progressive CR of up to 40%, using either a low-fat or low-carbohydrate diet with equal protein content. Mice fed a regular chow diet ad libitum served as controls. Body mass, hindlimb muscle mass, fat mass, energy expenditure, and glucose tolerance were compared between the groups.

Results: Initially low-fat and low-carbohydrate groups had similar body mass, which was 30% greater compared with controls. CR induced similar weight loss in low-fat and low-carbohydrate groups. This weight loss was mainly due to fat loss in both groups. Energy expenditure of freely moving mice did not differ between the groups. Glucose tolerance improved compared with the values before CR and in controls but did not differ between the diets.

Conclusions: Dietary carbohydrate or fat content does not affect improvements in body composition and metabolic health in obese mice exposed to CR with fixed energy and protein intake.