Weight Loss With a Low-Carbohydrate, Mediterranean, or Low-Fat Diet

Abstract

Previous trials have shown that a low-carbohydrate diet high in fat and protein may result in weight loss and exert positive metabolic effects. The Mediterranean diet, with moderate fat and high in monounsaturated fat, provides cardiovascular benefits, but weight loss has not been documented. This 2-year trial assigned 322 moderately obese subjects, predominantly males, whose body mass index (BMI) was at least 27 (or who had either type 2 diabetes or coronary heart disease) to 1 of 3 diets: low fat or Mediterranean, both with restricted calories, or low-carbohydrate without caloric restriction. Participants had a mean age of 52 years and a mean BMI of 31; 86% were males. Rates of adherence to the assigned diet approximated 95% after 1 year and 85% at 2 years. Subjects assigned to the Mediterranean diet consumed the most dietary fiber and had the highest ratio of monounsaturated to saturated fat. Those taking the low-carbohydrate diet ate the least carbohydrate and had the largest amounts of fat, protein, and cholesterol. They were likelier than others to have urinary ketones detected. Weight loss averaged 2.9, 4.4, and 4.7 kg for the low-fat, Mediterranean, and low-carbohydrate groups, respectively. For the 272 subjects who completed the trial, the respective weight losses were 3.3, 4.6, and 5.5 kg. The relative reduction in the ratio of total cholesterol to high-density lipoprotein cholesterol was 20% in the low-carbohydrate group and 12% in the low-fat group. Levels of high-sensitivity C-reactive protein declined significantly in the Mediterranean and low-carbohydrate groups. Among 36 participants with diabetes, changes in fasting plasma glucose and insulin levels were more favorable for patients taking the Mediterranean diet than those on the low-fat diet. Changes in bilirubin, alkaline phosphatase, and alanine aminotransferase were comparable in all 3 diet groups. This 2-year trial suggests that the low-carbohydrate and Mediterranean diets promote weight loss comparable to that achieved with a low-fat diet and are just as safe. It seems feasible to individualize dietary interventions according to metabolic considerations and personal preferences.