Many of us think we’re in control of what we eat and that, coupled with what we do, dictates our shape and size. It’s physics after all - if you eat too much and move too little, you put on weight; do the opposite, and you lose it. Genes, the theory goes, have minimal if any effect on our size.

But what if we’re wrong? What if our genes have a powerful influence over how we put on weight, and why many struggle to lose it?

Over the past two decades, this once controversial idea has gained acceptance and has inspired the work of Giles Yeo. His research on the genetics of obesity at Cambridge University reveals the powerful ways in which our genes, which function within our brains, influence our eating behaviour.

These genes are far better suited to times of food scarcity. Fast forward to the modern diet, packed with sugar and fat, and our genetic makeup quickly becomes a recipe for disaster.

Producer: Beth Eastwood