In order to eat fewer calories than you need, you have to determine how many calories you actually need. For this purpose, we begin by assuming that you do no exercise.

Adult males can calculate their approximate energy needs using the following formula:

A. Basal Metabolic Rate (Body weight multiplied by 12)

B. Activity One (third body weight multiplied by the number of hours you don't sleep, typically 16 hours)

C. Digestion: A + B multiplied by 10%

D. Required Calories: A + B + C

The "Basal Metabolic Rate" is the number of calories a man of that weight would burn just to keep the heart beating, the lungs pumping, etc. You would just burn your basal metabolic rate worth of calories if you slept 24 hours per day. "Activity" is approximately the amount of calories a person would expend by spending his or her whole day sitting around. Any deviation from sitting around can be considered exercise and added to the amount expended.

Adult females can calculate their approximate energy needs using the same formula, except that A (the "Basal Metabolic Rate") is determined by multiplying body weight times 11 (e.g., 130 lbs. x 11 = 1430). Once you've determined how much you need to eat, stop eating that much. In order to reduce your calorie intake to an amount less than you require, you'll have to keep track of how much you eat. The best way to do this is to buy a book that includes an extensive list of foods and the number of calories each item contains. A good, thorough listing takes many, many pages; don't buy something that just contains a one-page list of "sample caloric values," because you eat lots of different things. If you don't want to buy a book, you can just eat nothing but packaged foods that indicate the number of calories they contain.

Now that you have the means to keep track of your caloric intake, you need to set a daily allowance and stick to it. It is very difficult to function on a diet that is more than 500 calories under your requirement, and we don't recommend trying to follow such a diet.

Now that you've calculated your daily allowance, you just need to keep track of what you eat and stick to your diet. When you knock down your intake, your body notices and it lets you know by making you feel hungry. Ignore this. Eat lots of celery, eat low-fat, high-fiber meals, and drink lots of water.

SoYouWanna know more? Check out our full-length article SYW lose weight?