There's an idea currently circulating that sugar is the main reason why healthy traditional cultures end up obese and sick. It’s easy to find non-industrial cultures that are lean and don’t eat much sugar, and it’s easy to find industrial cultures that are obese and eat a lot of it. But many factors are changing simultaneously there. We could use the same examples to demonstrate that blue jeans and hair gel cause obesity. If sugar is truly the important factor, then cultures with a high sugar intake, but an otherwise ancestral diet and lifestyle, should also be overweight and sick. Let’s see if that's true.