The ACT-OUT Trial: ACTivity OUTcomes Based on High Carbohydrate or High Fat Diet in Metabolic Syndrome

Current obesity prevention emphasizes caloric restriction and avoidance of high fat foods. The result is an approach that replaces dietary fat with carbohydrates. There has, however, since been an obesity epidemic with an increased prevalence of metabolic syndrome (MetS) and type II diabetes. Negative results from trials of low fat diets for weight loss, prevention of heart disease and malignancies are consistent with the inadequacy of low fat/high carbohydrate approach. One of the findings of trials comparing low fat, calorie reduced diets to ad lib carbohydrate restricted diets is that subjects randomized to a low carbohydrate intake lose more weight despite equivalent intake. This equates to a 200 kcal/day greater weight loss on a carbohydrate restricted diet. Some investigators have speculated the metabolic advantage of carbohydrate restriction is due to increased energetic costs of gluconeogenesis. Alternatively, carbohydrate restriction is associated with increases in spontaneous physical activity. This protocol has three aims. First, adherence to a carbohydrate restricted diet in subjects with metabolic syndrome will cause an increase in spontaneous physical activity, independent of weight changes. Second, cardiometabolic risk factors (ApoB, TG, HDL, blood pressure, CRP) will show greater improvement on a carbohydrate restricted diet compared to a low-fat, high carbohydrate diet. Finally the investigators will interview a sub-sample of participants to better understand quality of life issues with respect to the dietary assignment or lifestyle intervention. The investigators will recruit 72 participants with MetS, from the Metabolic Syndrome Program at St. Paul's Hospital, Vancouver. Individuals will be randomized to either a low-carbohydrate diet or a calorie restricted, low fat diet and followed for 6 months. The investigators will measure body composition with bioelectrical impedance at baseline, 3 and 6 months. The investigators will also examine cardiometabolic changes due to the standard lifestyle intervention compared to the carbohydrate restricted treatment. The investigators will examine blood pressure, triglycerides, LDL-chol, HDL-chol, C-reactive protein, apolipoprotein B, glucose, insulin, hemoglobin A1c and leptin at baseline, 3 and 6 months. The investigators will use accelerometers to assess changes in physical activity. The investigators will use three-way repeated-measures ANOVA, with changes in body weight and insulin levels as covariates in the model with time as the repeated factor for statistical analyses.