Rather obviously, the low-cal diet states that if you plan to diet successfully, it is essential to eat fewer calories than you actually use.
Definition of a calorie?
A calorie is a measurement of the energy provided by food. The calorie is the the amount of energy required to raise the temperature of one gram of water by one degree celsius. If a food has higher calories, then it will provide your body with more energy when it is eaten.
Low-cal food types include watercress, tomatoes, melon, beef based meals, and low-fat cheese.