A negative calorie food is a food that requires more energy to be digested than it provides. There is no scientific evidence that any foods claimed as negative calorie foods are. Foods that are claimed to be negative in calories are mostly low-calorie fruits and vegetables such as grapefruit, lemon, lime, apple, and lettuce. Celery, a commonly cited negative calorie food, actually requires only about 10% of its food energy content to be digested. Celery is very low in nutrients and calories. However, that does NOT mean it takes more calories to digest the celery than the celery contains. The only true Zero-calorie beverages, is water. The body does actually burn calories in the process of digesting, resulting in a negative loss of calories. My advice is not to get too caught up in the idea of negative calorie foods. Exercising and eating balanced meals is a healthy weight loss plan. Nutrition is just one part of the equation when it comes to a healthy lifestyle, exercise is key too. Everyone should exercise for 30 to 40 minutes at least 3 times a week. If you are looking for a free nutrition and workout plan on line I highly recommend, Spark People at www.sparkpeolpe.com. I think it is a great tool for dieting and it is easy to use.