Instead of reaching for the latest fad diet, the best way to lose weight successfully is a personalised approach - diets tailored to your individual biology and psychology. In a groundbreaking national experiment, Dr Chris van Tulleken and Professor Tanya Byron join a team of leading experts to put 75 overweight volunteers on diets designed to tackle the specific reasons why they eat too much. The volunteers are put through a series of tests at a residential clinic to understand how their genes, hormones and psychology influence their eating behaviour. They are then put on the diets the experts believe are best suited to them. Can science succeed where other diets have failed?