In only a few decades, there are now more obese people on the planet than there are undernourished. When it comes to getting fat, we’ve come to believe it’s as simple as ‘calories in’ versus ‘calories out’ – if you want to shed the kilos, you need to burn more calories than you consume. But not all calories are the same. Some people absorb calories more efficiently and it matters what types of foods your calories are coming from. Sugar is now being proposed by experts as the new dietary villain that’s making us fat and sick. Dr Maryanne Demasi investigates the bitter truth about the dangers of a sweet diet.