Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 23651522 · doi:10.1017/S0007114513000548
What was done
A systematic search was conducted through August 2012 across MEDLINE, CENTRAL, ScienceDirect, Scopus, LILACS, SciELO, ClinicalTrials.gov, and grey literature without language restrictions. The review included randomised controlled trials in adults comparing a very-low-carbohydrate ketogenic diet (VLCKD; <=50 g carbohydrates/day) with a conventional low-fat diet (LFD; <30% energy from fat) with at least 12 months of follow-up. The primary outcome was body weight, and secondary outcomes included triglycerides, HDL-C, LDL-C, systolic and diastolic blood pressure, glucose, insulin, HbA1c, and C-reactive protein levels.
What was found
Thirteen studies met inclusion criteria. VLCKD resulted in statistically significant differences across five outcomes compared with LFD: - Body weight: weighted mean difference -0.91 kg (95% CI -1.65 to -0.17, 1415 patients) - Triglycerides: weighted mean difference -0.18 mmol/l (95% CI -0.27 to -0.08, 1258 patients) - Diastolic blood pressure: weighted mean difference -1.43 mmHg (95% CI -2.49 to -0.37, 1298 patients) - HDL-C: weighted mean difference 0.09 mmol/l (95% CI 0.06 to 0.12, 1257 patients) - LDL-C: weighted mean difference 0.12 mmol/l (95% CI 0.04 to 0.20, 1255 patients) No statistically significant differences were reported in the overall analysis for systolic blood pressure, glucose, insulin, HbA1c, or C-reactive protein.
Why it matters
This review shows that very-low-carbohydrate ketogenic diets can achieve slightly greater weight loss and improvements in specific cardiovascular risk markers than conventional low-fat diets at 12 months or longer, though they concurrently increase LDL-C.
Limits
The between-group weight difference after 12 or more months was small (less than 1 kg), which may limit clinical significance. The abstract does not report dietary adherence rates, participant dropout rates, adverse events, or hard cardiovascular clinical endpoints.
Cited by
- context Therapeutic ketogenic diets typically restrict carbohydrate intake to 30 to 40 grams per day for conditions like traumatic brain injury, concussion, and Alzheimer's disease.