The phrase negative calorie food is used to refer to foods that require more energy to digest than they provide nutritionally. Although no food can actually have negative calories, some foods provide extremely few. If these foods require more energy than they provide to digest, the effect of consuming them results in a net energy loss.Low nutrient, high cellulose foods like celery are generally agreed to consume slightly more energy to digest than they provide nutritionally. These foods may be consumed within a weight-loss diet to potentially relieve the feeling of hunger without contributing to total caloric intake. Limiting a diet to only these foods could result in malnutrition.There are claims that some foods require more energy than others to digest, but there is currently no evidence to support this. Many vegetables and fruits promoted as "negative calorie" contain more calories than are consumed in digestion, but they may have a low amount of calories relative to the amount of satiation they provide. References^ http://www.snopes.com/food/ingredient/celery.asp