Conventional low fat diets produce modest wegiht loss at best and the results are not well maintained. More recently there has been interest in low glycemic index and high protien diets wiht some evidence that these produce better fat loss and improvement in cardiovascular risk factors. This trial aims to evaluate these different approaches and compare the outcomes over 12 weeks. Major outcomes are weigth loss, body composition change, blood lipids change, measures of glucose homeostasis, insulin resistance, leptin and CRP.