Writer: Martha Filipic

Source: Sharron Coplin & Lydia Medeiros

How many calories should I eat per day?

Your daily calorie needs are likely different than those of your best friend, your sister and your spouse: It all depends on your age, your activity level, your metabolism and your weight. But a sure clue that you're eating too many calories is that you're gaining weight. Eating 2,000 calories a day when you need only 1,850 will put 15 extra pounds on you each year.

One basic rule to know is that 3,500 calories equals one pound of body fat. If you eat 3,500 calories less than what you need over the course of a week, for example, then you should lose about a pound.

The National Research Council has come up with a formula to estimate daily caloric needs, but it's a bit too complicated to reproduce here. To get close, you can use a rough estimate based on your body weight and activity level:

• Inactive. This is where the typical office worker falls. If you get little or no exercise, you'll burn anywhere from 11 to 16 calories per pound of body weight a day.
• Moderately active. You make a point to take a brisk walk or go cycling for 30 minutes several times a week. Moderately active people burn about 13 to 18 calories per pound of body weight a day.
• Very active. This includes 60 minutes of exercise at least five days a week. Very active people burn about 15 to 20 calories per pound of body weight a day.

Keep in mind that these are only rough estimates. Some people burn only 11 calories per pound per day. Some very active people -- professional football players, for example -- may burn 26 calories per pound per day. Another thing to consider: Bigger bodies burn more calories than smaller bodies. That's an important point for people who lose weight.

Let's say you weigh 180 pounds and are (to be honest) an inactive person, you'll need anywhere from 1,980 to 2,880 calories a day to maintain your body weight. That's a big range. But you decide to cut back to about 1,500 calories a day, and, over the course of time, you lose 30 pounds. At 150 pounds, the calorie range for an inactive person is 1,650 to 2,400 a day to maintain your weight. If you go off your diet and back to your old eating habits, your weight will increase unless you increase your activity at the same time. That's why nutritionists emphasize that a permanent lifestyle change is what's really necessary to lose weight and keep it off.

Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH 43210-1044, or filipic.3@osu.edu.

Editor: This column was reviewed by Sharron Coplin, registered dietitian and nutrition associate for Ohio State University Extension and Lydia Medeiros, associate professor of human nutrition with the College of Human Ecology.