Obesity is a detrimental disease that affects up to 60 % of domestic cats in North America. It is generally accepted that diet plays a fundamental role in the development of obesity in cats. However, few research studies investigate the role of macronutrients, protein, carbohydrates, and fats, in obesity. The aim of the present study is to evaluate how a low carbohydrate diet may benefit both lean and obese cats compared to both a low protein and a low fat diet, which each have a higher carbohydrate content.