The negative calorie diet has been around for years. It’s based on the notion that some foods require more calories to become digested than the calories they contain and thus they create a calorie deficit that may help you lose weight. The foods that have "negative" calories includes leafy vegetables, citrus fruits and of course celery. Unfortunately this notion is simply false: even if we accept that some foods may require slightly more calories to get digested than the calories they contain (although there is absolutely no evidence that this is true), at the end of the day, this deficit will be minimal, maybe about 10-20 calories. In all probability, any weight loss will occur due to the fact that by eating more foods high in fiber and water content we replace foods high in fat and calories. So, the negative calorie diet simply doesn’t work.