How Much Should You Be Eating? Your Calorie RequirementsBy Ali Hale
If you're trying to lose or gain weight, you need to know how many calories you should be eating. Calories are units of energy in food, and to keep your weight stable, you need to take in the same amount of energy as you expend. If you want to lose weight, you need to use more energy than you take in; if you want to gain weight, you need to take in more energy than you use.
How many calories do I need?
There's a simple formula, called the Harris Benedict equation, which you can use to work out how many calories you personally require:
655 + (4.3 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years) OR 655 + (9.6 x weight in kg) + (1.8 x height in cm) - (4.7 x age in yrs)
66 + (6.3 x weight in pounds) + (12.9 x height in inches) - (6.8 x age in years) OR 66 + (13.7 x weight in kg) + (5.0 x height in cm) - (6.8 x age in yrs)
This will give you a figure called your "Basal Metabolic Rate" or BMR. This is how many calories your body burns up just to keep you alive, regardless of any exercise or activity you carry out.
Here's an example for an adult woman who weighs 180lbs, is 64" (5 ' 4") tall, and 30 years old:
655 + (4.3 x 180) + (4.7 x 64) - (4.7 x 30) = 655 + (774) + (300.8) - (141) = 1,588
(Remember that this is just the BMR -- the actual calories per day for weight maintainance will be higher.)
In order to calculate how many calories you're using in full, you need to multiply your BMR by a percentage:
- Sedentary (no exercise, at a desk most of day): BMR x 20 percent
- Light Activity (no exercise, on feet during day, eg. shop work): BMR x 30 percent
- Moderately Active (exercise 3 + days a week for at least 30 minutes): BMR x 40 percent
- Highly Active (exercise 5 + days a week for at least 30 minutes): BMR x 50 percent
So, if the woman in the example above has a desk job and gets no exercise:
1,588 * 20% = 1,905.6 calories.
(To multiply by a percentage, divide your figure by 100 then multiply by 120 for 20%, 130 for 30%, and so on.)
The figure that you have now tells you how many calories you need to maintain your weight.
How many calories should I eat if I want to lose or gain weight?
Most people who are interested in their calorie requirements want to either lose weight or to gain weight.
In order to lose weight, you should reduce your calorie figure by 500 to lose weight at a safe rate of 1lb/week (though don't drop below 1,100 calories). You may find it helps if you do more exercise in order to increase your calorie requirement. The woman in the example above would be on a daily calorie limit of 1,405.6 calories if she wanted to lose 1lb/week. If you are very overweight, you may be able to reduce your calorie figure by 750 or 1,000, but again, be careful not to drop below 1,100 calories per day.
In order to gain weight, you should increase your calorie figure by 500 (if you struggle to eat enough, snack on calorie-dense foods like nuts).
It's always a good idea to seek your doctor's advice before embarking on a weight-loss or weight-gain diet, as there may be other factors involved than just how many calories you are eating.
Ali Hale has been interested in diet and nutrition since losing 50lbs and transforming from a shy, chubby teenager to a slim, happy and healthy woman. She has written more about daily calorie intake on her popular "healthy living for busy people" blog, The Office Diet.