This study was designed to compare the effects of an energy-reduced, isocaloric very-low-carbohydrate, high-fat (VLCHF) diet and a high-carbohydrate, low-fat (HCLF) diet on weight loss and cardiovascular disease (CVD) risk outcomes.
Despite the popularity of the VLCHF diet, no studies have compared the chronic effects of weight loss and metabolic change to a conventional HCLF diet under isocaloric conditions.
A total of 88 abdominally obese adults were randomly assigned to either an energy-restricted (∼6 to 7 MJ, 30% deficit), planned isocaloric VLCHF or HCLF diet for 24 weeks in an outpatient clinical trial. Body weight, blood pressure, fasting glucose, lipids, insulin, apolipoprotein B (apoB), and C-reactive protein (CRP) were measured at weeks 0 and 24.
Weight loss was similar in both groups (VLCHF −11.9 ± 6.3 kg, HCLF −10.1 ± 5.7 kg; p = 0.17). Blood pressure, CRP, fasting glucose, and insulin reduced similarly with weight loss in both diets. The VLCHF diet produced greater decreases in triacylglycerols (VLCHF −0.64 ± 0.62 mmol/l, HCLF −0.35 ± 0.49 mmol/l; p = 0.01) and increases in high-density lipoprotein cholesterol (HDL-C) (VLCHF 0.25 ± 0.28 mmol/l, HCLF 0.08 ± 0.17 mmol/l; p = 0.002). Low-density lipoprotein cholesterol (LDL-C) decreased in the HCLF diet but remained unchanged in the VLCHF diet (VLCHF 0.06 ± 0.58 mmol/l, HCLF −0.46 ± 0.71 mmol/l; p < 0.001). However, a high degree of individual variability for the LDL response in the VLCHF diet was observed, with 24% of individuals reporting an increase of at least 10%. The apoB levels remained unchanged in both diet groups.
Under isocaloric conditions, VLCHF and HCLF diets result in similar weight loss. Overall, although both diets had similar improvements for a number of metabolic risk markers, an HCLF diet had more favorable effects on the blood lipid profile. This suggests that the potential long-term effects of the VLCHF diet for CVD risk remain a concern and that blood lipid levels should be monitored. (Long-term health effects of high and low carbohydrate, weight loss diets in obese subjects with the metabolic syndrome; http://www.anzctr.org.au; ACTR No. 12606000203550).