Effects of energy-matched low- versus high-carbohydrate diets on glycaemic control, lipid profile, and body composition in healthy adults: a systematic review and meta-analysis of randomised controlled trials.

Low-carbohydrate diets produced greater reductions in fasting blood glucose compared with high-carbohydrate diets under energy-matched conditions.

• Pooled effect size: Hedges' g = -0.364; 95% CI -0.709 to -0.019; P < 0.001
• 18 RCTs involving 905 participants were included in the meta-analysis
• LC diets were defined as ≤44% of total daily caloric intake from carbohydrate; HC diets as ≥45% TDCI
• Random-effects model was used to calculate pooled effect sizes
• Studies were identified through systematic searches of PubMed and secondary sources up to April 2025

Low-carbohydrate diets produced greater reductions in fasting insulin compared with high-carbohydrate diets.

• Pooled effect size: Hedges' g = -0.190; 95% CI -0.361 to -0.014; P = 0.034
• Only non-medicated, disease-free adults were included in eligible studies
• Studies were required to compare energy-matched dietary interventions
• Effect was considered statistically significant at P = 0.034

Triglycerides decreased significantly more under low-carbohydrate compared with high-carbohydrate diets.

• Pooled effect size: Hedges' g = -0.379; 95% CI -0.540 to -0.219; P < 0.001
• This was one of the stronger effect sizes observed across all lipid outcomes
• Effect was consistent and statistically significant

HDL-cholesterol increased significantly more under low-carbohydrate compared with high-carbohydrate diets.

• Pooled effect size: Hedges' g = 0.389; 95% CI 0.229 to 0.550; P < 0.001
• This represented the largest statistically significant effect among lipid outcomes
• The positive Hedges' g value indicates a favorable increase in HDL-C under LC conditions

High-carbohydrate diets led to greater reductions in LDL-cholesterol compared with low-carbohydrate diets.

• Pooled effect size: Hedges' g = -0.225; 95% CI -0.406 to -0.043; P = 0.009
• This was the only lipid outcome where HC diets showed a significant advantage over LC diets
• No significant between-diet effects were found for total cholesterol

Low-carbohydrate diets reduced body mass to a greater extent than high-carbohydrate diets under energy-matched conditions.

• Pooled effect size: Hedges' g = -0.183; 95% CI -0.349 to -0.017; P = 0.031
• Effect was statistically significant despite energy-matching between dietary conditions
• This finding suggests macronutrient composition influences body mass independent of total caloric intake

Low-carbohydrate diets reduced fat mass to a greater extent than high-carbohydrate diets, with no significant effect on fat-free mass.

• Fat mass pooled effect size: Hedges' g = -0.304; 95% CI -0.548 to -0.059; P = 0.015
• No significant effect was observed for fat-free mass between LC and HC diets
• The differential effect on fat mass without affecting fat-free mass suggests LC diets may preferentially reduce adipose tissue

Most metabolic and anthropometric effects of low- versus high-carbohydrate diets did not depend on exercise status.

• The meta-analysis included 18 RCTs with 905 total participants
• Exercise status was evaluated as a potential moderator of dietary effects
• The authors concluded that evidence can guide carbohydrate intake recommendations 'in diets where total caloric intake remains unchanged'
• This finding was noted in both the abstract and conclusions of the paper