As obesity escalates, the diet business is booming. In this four-part series, Jacques Peretti investigates the connections between obesity and weight loss, and confronts some of the men making a fortune from our desire to become thin.

Jacques examines the scientific reasons why so many diets fail long term and why - in spite of this failure - we go back to them again and again. He also speaks to a former director of Weight Watchers and meets other industry leaders, including Slimfast billionaire Danny Abrahams and Pierre Dukan, of the Dukan diet.