What is a low calorie diet?
A low calorie diet is a diet that consumes less calories than your body uses.
That is, if your body burns 2500Kcal and you eat only 2000Kcal, you are following a low calorie diet.
What is a low calorie diet for you may not be for your colleague next door.
It is important to know the calories you use daily, since person A can spend 2000Kcal daily and person B 3000Kcal daily, a 2500Kcal diet will be hypercaloric for person A and hypocaloric for person B.
Hypocaloric diets are used to lose fat / weight.