Since it is clear that it is the amount of unneeded calories in the body that lead to weight gain, you have to create a calorie deficit. This is done by eating less than your body burns off. Different people have different calorie requirements and your exact calorie need depends on several factors, including your gender, age, weight and activity levels. There are several online calorie calculators that can help you work out your daily requirement. After calculating that, you need to record your calories intake against what your body needs. This is important because if you eat more calories than you burn, you add weight. As such, counting your calories helps you monitor your calories intake against your body’s calorie needs.