We all think we know the basics of weight loss. It is all about consuming fewer calories than you burn. Eat less, move more. Calories in, calories out. But there’s much more to it than these simple equations, as a trip to the enormous Pennington Biomedical Research Center in Baton Rouge, Louisiana - a hub of such research - shows. In this episode, we break down the science of why it’s so hard to lose weight, and look at what the kinds of stories heralded as a weight-loss success really look like in practice.