Long-term effects of weight loss with a very low carbohydrate and low fat diet on vascular function in overweight and obese patients

Wycherley TP, Brinkworth GD, Keogh JB, Noakes M, Buckley JD, Clifton PM. (Commonwealth Scientific and Industrial Research Organization, Food and Nutritional Sciences; School of Molecular and Biomedical Science, University of Adelaide; and Nutritional Physiology Research Centre and Australian Technology Network Centre for Metabolic Fitness, Sansom Institute for Health Research, University of South Australia). Long-term effects of weight loss with a very low carbohydrate and low fat diet on vascular function in overweight and obese patients. J Intern Med 2010; 267: 452-461. Objective. To compare the effects of an energy reduced very low carbohydrate, high saturated fat diet (LC) and an isocaloric high carbohydrate, low fat diet (LF) on endothelial function after 12 months. Design and Subjects. Forty-nine overweight or obese patients (age 50.0 ± 1.1 years, BMI 33.7 ± 0.6 kg m^-2) were randomized to either an energy restricted (∼6-7 MJ), planned isocaloric LC or LF for 52 weeks. Body weight, endothelium-derived factors, flow-mediated dilatation (FMD), adiponectin, augmentation index (AIx) and pulse wave velocity (PWV) were assessed. All data are mean ± SEM. Results. Weight loss was similar in both groups (LC -14.9 ± 2.1 kg, LF -11.5 ± 1.5 kg; P = 0.20). There was a significant time × diet effect for FMD (P = 0.045); FMD decreased in LC (5.7 ± 0.7% to 3.7 ± 0.5%) but remained unchanged in LF (5.9 ± 0.5% to 5.5 ± 0.7%). PWV improved in both groups (LC -1.4 ± 0.6 m s^-1, LF -1.5 ± 0.6 m s^-1; P = 0.001 for time) with no diet effect (P = 0.80). AIx and VCAM-1 did not change in either group. Adiponectin, eSelectin, tPA and PAI-1 improved similarly in both groups (P < 0.01 for time). Conclusion. Both LC and LF hypoenergetic diets achieved similar reductions in body weight and were associated with improvements in PWV and a number of endothelium-derived factors. However, the LC diet impaired FMD suggesting chronic consumption of a LC diet may have detrimental effects on endothelial function.