here is the Harris- Benedict equation in more detail
It is important to familiarise yourself with your actual metabolic rate, that is the rate at which your body utilises and burns calories. The only way to lose weight is to burn MORE calories than the amount you consume. Once you understand your bodys metabolic rate, you will be one step closer to achieving your weight goal- be it loss, maintenance or gain.
There are a number of ways which you can calculate your Basal Metabolic rate (BMR) and Active Metabolic rate (AMR). To calculate your BMR you can use the popular Harris-Benedict equation:
Lets Calculate your BMR:
Women
655 + (9.6 x wt in kg) + (1.8 x ht in cm) - (4.7 x age in yrs)
Example: you are 165 lbs (75kg), 5'4" tall (64in) and 32 years old
your BMR is : 655 + (9.6 x 75) + (1.8 x 163) - (4.7 x 32) OR
655 + (720) + (293) - (150) = 1518 calories
note = kg = lbs divided by 2.2, cm = inches multiplied by 2.54
Your BMR indicates the minimum number of calories that your body needs each day in order to function while at rest, such as heartbeat, breathing and blood flow. That is how many calories your body needs to simply operate for 24 hours without exerting any extra energy.
Your AMR is defined a your BMR plus the added calories you need each day to support basic movement and activity. Because your AMR varies based upon your level of activity, it will be higher the more active you are. To calculate your AMR, multiply your BMR according to your activity level.
Extra light = 1.3 ( cooking cleaning ironing driving standing etc)
Light = 1.3 ( golf, walking 3 mph, child care, housework)
Moderate = 1.6 ( cycling, tennis, dancing, walking 3.5-4.0mph)
Heavy = 1.9 (football, climbing, aerobic classes)
Referring to the BMR example lets calculate your AMR
Women
Your BMR is 1516 calories and your activity level is moderate
1516 x 1.6 = 2426 calories.
Now that you know what your basal and active metabolic rates are, you should know how to apply them to your daily life. In order to maintain your desired weight, your daily calorific intake should equal your AMR (+/- 100 calories). By consistently eating more calories than your AMR you will store these extra calories as fat- whether or not they originated from protein, carbs, fat or alcohol, you will end up gaining weight.
If you want to lose weight, then in order to do so both safely and effectively over a prolonged period of time, you should eat enough calories each day at least equivalent to your BMR. However if you take in significantly fewer calories than your daily calorific requirement for an extended period of time then your body will lower its metabolism and begin to conserve energy for survival and essentially cannibalise its muscles.
phew--- hope this helps guys.