Do Ketogenic Diets Produce Greater Weight Loss than Higher-Carbohydrate Diets Under Comparable Prescribed Energy Conditions? A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background/

Objectives

Whether ketogenic diets provide greater weight-loss benefits than higher-carbohydrate diets when prescribed energy intake or targeted energy deficit are comparable remains uncertain. This systematic review and meta-analysis evaluated their effects on body weight change in adults with overweight or obesity.

Methods

Following PRISMA 2020, PubMed, Scopus, and Web of Science were searched for randomized controlled trials comparing ketogenic diets with higher-carbohydrate diets under matched energy prescriptions. Ketogenic diets were defined as providing ≤50 g carbohydrate/day or ≤10% of total energy from carbohydrate. A random-effects meta-analysis used restricted maximum likelihood estimation and the Hartung-Knapp adjustment. Risk of bias and certainty of evidence were assessed using RoB 2 and GRADE, respectively.

Results

Eight reports representing seven studies were included in the systematic review; six studies comprising 259 participants contributed to the meta-analysis. Ketogenic diets were associated with slightly greater weight loss than higher-carbohydrate diets (MD = -1.49 kg; 95% CI: -2.41 to -0.58; p = 0.008; I2 = 0%). Estimates remained similar after alternative imputations of change-score standard deviations, exclusion of the trial at high risk of bias, and leave-one-out analyses. In three trials meeting the prescribed protein-matching criterion, the effect remained directionally consistent but was imprecise and compatible with no difference. Certainty of evidence was low because of risk of bias and imprecision.

Conclusions

Under comparable prescribed energy conditions, ketogenic diets may produce a small additional reduction in body weight. However, predominantly short-term evidence, uncertainty regarding achieved energy and protein intakes, the absence of a synthesis of body composition, and low certainty of evidence limit confidence in the magnitude, durability, and clinical significance of this advantage.