In simple terms, the low calorie diet says that if you want to lose weight, the most important step is to consume fewer calories than you actually use.
So what is a calorie?
A calorie is a unit of measurement for energy. A 'calorie' is the the amount of energy required to raise the temperature of one gram of water by one degree celsius. If a food type has higher calories, then it will provide your body with more energy to use when it is eaten.
Low-cal food types include bok choy, tomato, grapefruit, burgers and steaks, and eggs.