Negative calorie

The designation Negative calorie is more of a misnomer than an actual term. Calories are simply units of energy (a dietician's Calorie, or kilocalorie, is the amount of energy it takes to heat 1 litre of water 1 degree Celsius). When it happens that more energy is required to break down a food item than is released from the chemical digestion of that foodstuff, a net loss of energy (calories) is experienced by the body. Some have chosen to deem these types of foods, such as celery, as containing "negative calories" leading to much confusion.