More people are now at risk from obesity than starvation. Our diet of ice cream, hamburgers, chocolate and other high-calorie foods is making us seriously fat. But while some are getting fatter, there are others who seem to be immune. A group of medical students agree to eat double their normal intake of calories for four weeks. Meanwhile Dr Carel le Roux explodes some of the common misconceptions about weight. Is it all about self-control and exercise? Or do we have a natural weight which our bodies strive to maintain despite our fluctuating levels of calorie intake and exercise? Busting myths and exposing facts this doc goes in search of what makes one person fat and another thin.