The number of calories you need to eat each day is determined by how much energy you need to maintain your lean mass and the internal functions of your body's processes (heart beating, lungs inhaling and exhaling, cell metabolism, any life-supporting function).

Your Basal Metabolic Rate (BMR) is the rate at which your body spends energy for maintenance activities each hour. You can learn how to calculate your own BMR using the instructions below.

How to calculate your BMR:

1) Divide your weight by 2.2 ( = your weight in kilograms)

Multiply that number by the BMR factor (1 for a man, .9 for a woman)

Multiply that number by 24 (for hours in a day)

This is your BMR.

2) Add that number to your activity level, which is:

Sedentary = 40-50% of your BMR

Light activity = 55-65% of your BMR

Moderate activity = 65-75% of your BMR

Heavy activity = 75-100% of your BMR

This is your activity level energy requirements.

3) Add the numbers from A and B together.

This is your daily calorie requirement.

You need to eat at least this much to maintain your current body weight.

To lose weight, cut about 500 calories per day (for a 2,000 calorie-per-day diet).

BMR Calculation Examples:

Jack weighs 190 pounds and has a moderate activity level:

Jack's BMR = (190/2.2) X 1 X 24 = 2,072 calories

Jack's Activity level lower limit = 2,072 X .65 = 1,347 calories

Jack's Activity level upper limit = 2,072 X .75 = 1,554 calories

Jack's Calories per day = 3,419 to 3,626 calories

Jill weighs 120 pounds and has a heavy activity level:

Jill's BMR = (120/2.2) X .9 X 24 =1,178 calories

Jill's Activity level lower limit = 1,178 X .75 = 884 calories

Jill's Activity level upper limit = 1,178 X 1 = 1,178 calories

Jill's Calories per day = 2,062 to 2,356 calories

BMR calculations are average estimations. Your actual BMR fluctuates, depending on these factors:

Age - younger people have a higher BMR. Older people have less lean mass.

Height - tall, thin people have a higher BMR.

Growth - children and pregnant women have a higher BMR.

Body Composition - people with more lean tissue have a higher BMR.

Fever - fever increases your BMR.

Stress - stress increases your BMR.

Inside/Outside Temperature - heat and cold both raise your BMR.

Fasting - lowers your BMR.