Long-term effects of a low carbohydrate, low fat or high unsaturated fat diet compared to a no-intervention control

Background and aim: Very low carbohydrate ad libitum diets have been shown to enhance weight loss without increasing cardiometabolic risk factors but no kilojoule-controlled trials have been conducted relative to no intervention. The aim of this study was to compare the changes in weight and other cardiovascular risk factors in 3 isocaloric energy-restricted diets to no-intervention control after 1 year. Methods and results: One hundred and thirteen subjects (age 47±10 years, BMI 32±6kg/m² with one additional cardiovascular risk factor) were randomly allocated to one of three isocaloric diets (VLC-very low carbohydrate, 60% fat, 4% carbohydrate, n=30; VLF-very low fat, 10% fat, n=30; HUF-high unsaturated fat, 30% fat, n=30) with intensive support for 3 months followed by minimal support for 12 months compared to a control group (no intervention, n=23). The estimated weight change was -3.0±0.2kg for VLC, -2.0±0.1kg for VLF, -3.7±0.01kg for HUF and 0.8±0.5kg for controls (P=0.065). After correcting for baseline values, decreases in body weight and diastolic blood pressure in the diet groups (-2.9±5.2) were significantly different to the increase in the control group (0.8±5.0) (P<0.05). No differences in cardiovascular risk factors were observed between the diet groups. Conclusion: Significant cardiometabolic risk factor reduction was observed equally with VLC, VLF and HUF diets after 15 months, compared to an exacerbation of risk factors in the control group. At a modest level of adherence, 3 months of intensive support on these dietary patterns confer an improvement in cardiometabolic profile compared to no dietary intervention after 15 months.