How Many Calories Do I Need?

When it comes to losing weight or maintaining a healthy weight, sooner or later, most people realize that calories count. For women, that hard truth usually hits us hard during our college years. The sad reality is that we usually need fewer calories than we would like to believe. The average person requires somewhere between 1,600 to 2,200 calories each day to maintain a healthy weight. Of course, depending on your activity level, degree of physical fitness, age, and gender, your needs may differ.

In order to know your caloric needs, calculate your basal metabolic rate (BMR), more commonly known as your “metabolism.” This will show you the number of calories your body requires to function properly at rest—before you factor in activity and exercise.

To roughly estimate your personal BMR, multiply your current weight in pounds by 10. If you weigh 150 pounds, for instance, your BMR is roughly 150 X 10, or 1500 calories. (A more complicated formula, known as the Harris-Benedict equation, takes into account gender, height and age. I've given you the equation at the bottom of this post). None of these formulas are perfect. Many factors affect your BMR. The leaner you are, the higher your BMR, and the more fat your body carries, the lower your BMR will be. Children, especially when going through rapid growth spurts, have a higher metabolism, as do pregnant women.

Once you calculate your BMR, it’s easy to figure out how many calories your body needs, based on how much energy you burn. To keep it simple, we can estimate based upon your average activity level.

If you are a typical couch potato, multiply your BMR by 20 percent (for example 1500 X 20% = 300). Someone who engages in light activity, such as walking around at work for several hours over the course of the day, will multiply her BMR by 30 percent. If your fitness level is moderate (say you exercise several times a week or have a physically active job) multiply your BMR by 40 percent. Finally, someone who is extremely active at work, or who gets moving at least four hours every day and rarely sits still, should multiply by 50 percent. Once you determine this number, add it to your BMR.

For example, the 150 pound sedentary person would add 1500 plus 300 (1500 x 0.20 = 300) to reach a total of 1800 calories.

If you want to lose weight, calculate the BMR for the weight you desire. For example, let's say you would rather weight 130 lbs. Your BMR would be 1300. If you stay pretty sedentary, your daily calorie allotment would be only 1560 calories (1300 + 1300 x 0.2). Now you can see that if you want to continue to eat the same way you did as a sedentary 150 lb person, you're going to have to either increase your daily activity level, or add on some serious exercise.

Once you know how many calories your body will burn, it's time to calculate the number of calories you actually eat every day. There are a number of good references available for this purpose. (Try www.nal.usda.gov/fnic/foodcomp/search).The important thing is to be honest. Study after study shows that most people are not aware of their portion sizes and frequently underestimate the amount that they eat, often by as much as 500 calories per day.


The Harris-Benedict Equation for BMR
For women:
BMR = 655 + (4.35 x W) + (4.7 x H) – (4.7 x A)
For men:
BMR = 66 + (6.23 x W) + (12.7 x H) – (6.8 x A)
W = weight in pounds
H = height in inches
A = age in years