Overweight and obesity are growing problems both in Canada and around the world. Obesity is associated with a number of chronic diseases including type 2 diabetes and CVD, which puts a tremendous burden on the health care systems in place. The present study sought to investigate whether there were differences in the effectiveness of three low-fat, hypo- and isoenergetic diets differing in protein:carbohydrate ratio, low protein (LP, 1 g protein:4 g carbohydrate), normal protein (NP, 1 g protein:2 g carbohydrate) or high protein (HP, 1 g protein:1 g carbohydrate), on weight loss and markers of the metabolic syndrome (MetS) in overweight women. Subjects were randomly assigned to receive one of three intervention diets, all of which included a 60 min exercise programme three times/week for 12 weeks. Of the total subjects, fifty-four overweight and obese local women with MetS risk factors completed the study. All groups had similar improvements in body weight, insulin sensitivity, lipid profile, blood pressure and fitness. Subjects reported that the NP diet was easier to comply with and achieved better improvements in body fat, waist circumference and waist:hip ratio, and preservation of lean mass compared with the other two diets. In conclusion, energy restriction and exercise both facilitate weight loss in overweight and obese subjects and reduce symptoms of the MetS. A diet with a 1:2 protein:carbohydrate ratio promoted better improvements than either the LP or HP diets, and may be superior in reducing long-term chronic disease risk in this population.