[Barry Sears] blames excess body fat on a hormonal response triggered by eating. When you consume carbohydrates, your level of insulin increases. It is insulins job to store excess carbohydrate calories in the form of fat for use later such as when theres a famine. (Old habits die hard; your cells still think youre out gathering nuts and berries, not living around the corner from a 7-Eleven.) Eat too many carbohydrates, Sears says, and your insulin levels soar, ordering the body not only to store fat but to keep any previously stored fat from being released. In other words, excess carbs not only make you fat, they make sure you stay fat, Sears says.