Mark Dolan journeys to Tonga, Mexico and Texas in search of some of the worlds fattest families. Obesity is not just an issue for individuals it affects whole families too. But is it the fault of bad parenting, or just bad individual choices? Tonga is the most obese nation in the world. And with a national diet of pork, lamb fat and mutton that's unlikely to change. Mark meets the Koloamatangi family, possibly the fattest on the island - with two generations all over 20 stone, who have prepared a Tongan feast in his honour featuring suckling pig. Mark learns there is a cultural belief that physical bulk is a sign of beauty and wealth. But is this tradition the reason Tonga has become the fattest nation on the planet? In Mexico, Mark learns the difference between being simply obese and super-morbidly obese when he meets Raymundo Cardenas Cruze, who is so ashamed of his weight he rarely leaves the house. In Texas he meets teenager Danielle who weights 29 stone. She has a four-year-old child who is also overweight and a morbidly obese brother, and her father died of an obesity related disease. She has always had an issue with her weight and was bullied at school, and then at 14 she became pregnant with her son. Jeremy. She feels that her weight has been encouraged by her grandmother always feeding her and is now concerned that her mother is repeating the cycle with her son, always giving him double portions. With so many people in America facing life as super-morbidly obese, the demand for drastic surgery is growing. Mark visits Light Dimensions, a clinic specialising in gastric band surgery, which is about to take on 46-stone Michael Herrera, one of its biggest clients ever.