We become fat because we eat too much. Why some eat more than others, however, is powerfully genetically controlled. The Director of Genomics/Transcriptomics at Cambridge explores some of these genes and observes: “Many genes have been identified that increase our risk of becoming obese and most of these function in the brain to influence food intake. Obese people find it hard to lose weight not because they are bad and lazy, but because they are fighting their biology.”