The negative calorie diet focuses on eating foods that take more calories to digest than are actually in the food. EG: an apple has 60 calories, but takes 85 to digest, so you have a net loss of 25 calories. Therefore, the more negative calorie foods you eat, the more weight you will lose. I've tried this; I didn't actually try the diet plan but I ate many of the foods. I looked skinnier, but I never weighed myself. It worked well for me!