Constant dieting leads to constant weight gain, something that people are not told when they sign up to slimming clubs. So why are some people condemned to a life as eternal dieters? And why does someone who has managed to lose half their body weight undo all their hard work and pile on the pounds again? Channel 5's Supersized season concludes with Got Thin - Got Fat Again, which explores why diets do not always work and how quickly and easily skinny success can turn into fat failure. We meet people who have lost weight but are now fat again, some more so than they were before the diet. Showing their before and after pictures, they explain the reasons why they wanted to lose weight in the first place and the triggers that caused them to put it back on. The average diet lasts just five and a half weeks, and the average woman will embark on 61 diets in her lifetime and spend around 31 years of her life trying unsuccessfully to lose weight. Within one year of their diet, 80% of people will gain weight, often more than they lost. Gina is 59 and weighs 24 stone. When she served in the Navy, she was fit and slim and her ideal weight. However, once she left the service she began comfort eating and ballooned in size. Having given up on fad diets,will Gina ever regain her once slim figure? Claudia has been dieting for almost half her life. Once she loses the weight, however, it doesn't take long for her to pile on the pounds once again. Now 13 stone, can she hold off the weight and regain her confidence? Hayley, 59, has been a yo-yo dieter for as long as she can remember. After suffering from severe medical complications due to her fluctuating weight, is there anyway out of this dieting cycle for her? The world of celebrity dieting is no different, as famous yo-yo dieter Josie Gibson reveals. Josie is determined not to go back up the scales, but what will it take for her to break her habit?