Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis

Context Carbohydrate-restricted diets may increase low-density lipoprotein cholesterol and thereby cardiovascular risk. Objective A systematic review and meta-analyses were 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 randomized controlled trials (n>100) with duration6months. Data Extraction Eight randomized controlled trials (n=1633; 818 carbohydrate-restricted diet, 815 low-fat diet) were included. Data Analysis Quality assessment and risk of bias, a random effects model, and sensitivity and subgroup analyses based on the degree of carbohydrate restriction were performed using Cochrane Review Manager. Results were reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocol. Results Carbohydrate-restricted diets showed no significant difference in low-density lipoprotein cholesterol after 6, 12, and 24months. Although an overall pooled analysis statistically favored low-fat diets (0.07mmol/L; 95% confidence interval [CI], 0.02-0.13; P=0.009], this was clinically insignificant. High-density lipoprotein cholesterol and plasma triglycerides at 6 and 12months favored carbohydrate-restricted diets (0.08mmol/L; 95%CI, 0.06-0.11; P<1x10(-5) and -0.13mmol/L; 95%CI, -0.19 to -0.08; P<1x10(-5), respectively). These favorable changes were more marked in the subgroup with very-low carbohydrate content (<50g/d; 0.12mmol/L; 95%CI, 0.10-0.14; P<1x10(-5) and -0.19mmol/L; 95%CI, -0.26 to -0.12; P=0.02, respectively). Conclusions Large randomized controlled trials of at least 6months duration with carbohydrate restriction appear superior in improving lipid markers when compared with low-fat diets. Dietary guidelines should consider carbohydrate restriction as an alternative dietary strategy for the prevention/management of dyslipidemia for populations with cardiometabolic risk.