Effects of ketogenic diet on obesity indices, lipid profile, and glycemic control parameters in athletes: a GRADE-assessed systematic review and meta-analysis of randomized controlled trials

Abstract

The ketogenic diet has revealed more beneficial effects on metabolic health. However, its net effects on atherogenic lipoproteins, adiposity, and glycemic control remain inconsistent. This systematic review and meta-analysis aimed to quantify the pooled effects of the ketogenic diet on lipid profile, obesity measures, and plasma glucose levels. The PubMed, Scopus, Web of Science, and Google Scholar databases were used for conducting a comprehensive systematic search up to January 2026. The random effect model was conducted to run statistical analysis. Fourteen studies were included in the current meta-analysis. Pooled estimates indicated that the ketogenic diet was associated with a significant improvement in HDL‑c levels (WMD: 9.18 mg/dL, 95% CI: 6.47, 11.90; P < 0.001). While, it revealed unfavorable effects on TC (WMD: 42.88 mg/dL, 95% CI: 29.40, 56.35; P < 0.001) and LDL-c (WMD: 44.41 mg/dL, 95% CI: 28.82, 59.99; P < 0.001) level too. In contrast, the ketogenic diet did not yield statistically significant pooled effects on TG (WMD: -1.96 mg/dL, 95% CI: -17.20, 13.27; P = 0.801), fat mass percentage (WMD: -0.54%, 95% CI: -1.31, 0.24; P = 0.174), fat-free mass percentage (WMD: -0.57%, 95% CI: -1.72, 0.59; P = 0.336), weight (WMD: -0.04 kg, 95% CI: -2.25, 2.17; P = 0.971), or plasma glucose (WMD: -2.30 mg/dL, 95% CI: -6.11, 1.51; P = 0.236). However, these null findings should be interpreted with caution, as the confidence intervals were wide and the number of contributing studies was small, limiting the power to detect modest but clinically meaningful differences. Also, it is worth noting that GRADE approach presented high quality of evidence for the TC and HDL-c values. The ketogenic diet consistently raises HDL‑c, even without significant pooled changes in weight or adiposity, suggesting weight‑independent hormonal pathways, a hypothesis requiring confirmation in larger trials. However, for outcomes where no significant pooled effect was observed (TG, body composition, and glucose), the current evidence is insufficient to rule out clinically meaningful effects. Larger, longer-term randomized clinical trials (RCTs) are urgently needed to clarify the net metabolic impact of ketogenic diets in exercising populations.