Simon goes to the doctor and finds out the bad news – like most us, he's fat - in fact he's borderline obese – and to make matters worse, he has type 2 diabetes. But he's not alone - world obesity rates have soared and so have heart disease and kidney problems - diabetes in the United States alone has increased an astonishing 900% in just 50 years. So how did we all get so fat so fast, and what is diabetes? Simon goes to the United States and talks to the experts including Professor Robert Lustig who tells him the problem is sugar and the food it lives in – low fat processed food that now dominates our diet. Simon goes to the supermarket, on taking a closer look at packaged food he is shocked to find almost everything contains surprising amounts of sugar. History expert Gary Taubes explains how fat has been demonised and sugar and refined carbohydrates got a free pass, which led to the 1990 food pyramid dominated by grains. We visit the lab of Professor Jenny Brand Miller who demonstrates how refined grains convert rapidly to glucose that spikes blood sugar levels. Back in the USA we see what happens to rats when they are fed a highly processed diet- they get fat, sick and diabetic just like humans do. To find out exactly how much fat Simon he enters the futuristic BodPod only to get the shocking result that he is 40% fat. An MRI scan reveals that most of this fat is packed inside his abdominal cavity, his pancreas carries excess fat, and his liver is a frightening one third fat. He's given 3 months to turn things around.