Effects of carbohydrate restricted diets on low density lipoprotein-cholesterol levels in overweight and obese adults: a systematic review and meta-analysis of large randomised controlled trials of at least 6 months

Abstract

Context: Carbohydrate restricted diets may increase low density lipoprotein-cholesterol and thereby cardiovascular risk. Objective: A systematic review and meta-analyses was conducted to compare the effects of very low, low and moderate carbohydrate higher fat diets versus high-carbohydrate low-fat diets on low density lipoprotein-cholesterol and other lipid markers in overweight/obese adults. Data Sources: Medline, PubMed, Cochrane Central, and CINAHL Plus were searched to identify large randomised controlled trials (n > 100) with duration ≥ 6 months. Data Extraction: Eight randomised controlled trials (n = 1633, 818 carbohydrate restricted, 815 low fat diet) were included. Data Analysis: Quality assessment and risk of bias, a random effects model, sensitivity and subgroup analysis based on the degree of carbohydrate restriction were performed using Cochrane Review Manager. Results were reported according to ‘Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocol’. Results: Carbohydrate restricted diets showed a none significant difference in low density lipoprotein cholesterol after 6, 12, and 24 months. While an overall pooled analysis statistically favoured low-fat diets [0.07 mmol/L; 95% CI 0.02, 0.13; p = 0.009] this was clinically insignificant. High density lipoprotein-cholesterol and plasma triglycerides at 6 and 12 months, favoured carbohydrate restricted diets [0.08 mmol/L, 95% CI 0.06, 0.11; p < 1x10-5 37 and -0.13 mmol/L, 95% CI -0.19, -0.08; p < 1x10-5] respectively. These favourable changes were more marked in the subgroup with very-low carbohydrate content (< 50 g/day) [0.12 mmol/L, 95% CI 0.10, 0.14; p < 1x10-5 40 and -0.19 mmol/L, 95% CI -0.26, -0.12, p = 0.02] respectively. Conclusions: Large randomised controlled trials of at least 6 months duration with carbohydrate restriction appear superior in improving lipid markers when compared to low-fat diets. Dietary guidelines should consider carbohydrate restriction as an alternative dietary strategy for the prevention/management of dyslipidaemia for populations with cardiometabolic risk