How many calories do you really need to eat each day? That’s the question as people continue on the road to instilling healthier habits and holding the line on weight gain.
It all comes down to numbers–calories in, calories out–and finding the right balance to maintain weight. Tip it too much toward intake and the pounds will pile on, but tilt it the other way, even slightly, and it’s just a matter of time before unneeded pounds drop off.
The trick, of course, is figuring out how many calories are enough, which requires estimating resting metabolic rate (RMR), the number of calories required just to stay alive.
About 20 percent of RMR is accounted for by the brain and nervous system. The liver gobbles up about 32 percent, while the heart and lungs each take about 10 percent of total calories. The rest goes to the kidneys (7 percent) and other tissues in the body (21 percent).
RMR varies from person to person. It declines with age but generally runs a little higher in men because of greater muscle mass, which burns more calories than does fat. That means a 160-pound man gets to eat a few more calories daily than a 160-pound woman.
RMR can be measured down to the calorie with sophisticated and costly medical equipment. Cheaper, hand-held devices streamline measurement and are used as marketing tools by health clubs. But for the vast majority of folks, RMR is easily estimated with a few simple calculations or by using an online RMR calculator (www.dallasdietitian.com/calcalc.htm).
To do the math yourself: Take body weight in pounds and multiply by 10. Then add about 20 percent to 40 percent more calories for a sedentary lifestyle; 40-60 percent for a more-active daily life and 60-80 percent for a highly active lifestyle. (Thus, a 120-pound moderately active person needs to eat approximately 1,680 calories–1,200 plus about 480 calories for activity–to maintain his or her weight, while a sedentary 150-pound person would need to consume about 1,800 calories daily–1,500 calories plus 300–to keep the bathroom scale steady.)
Even easier: Use the U.S. Dietary Guidelines, which recommend 1,600 calories a day for children, women and older adults; 2,200 a day for older children, teen girls, active women and most men and 2,800 a day for adolescent boys and active men.
Not surprisingly, weight loss is a different story and requires trimming calories below those required to maintain weight. One pound is equal to about 3,500 calories. Spread that over a week, and it works out to a deficit of about 500 calories a day–an amount that many weight-loss experts recommend achieving by cutting back on food (about 250 calories) and exercising a little more (to burn about 250 calories daily). If you do this, you’ll lose about a pound a week. Cut just 250 calories a day (125 in food, 125 in exercise), and lose about half a pound a week.
Or take a lesson from Thomas Wadden, director of the Weight and Eating Disorders Clinic at the University of Pennsylvania. For weight loss, he recommends eating 1,200 to 1,500 calories a day for women and 1,500 to 1,800 calories a day for men.
Of course, reducing calories almost certainly means counting them. Yet studies show that people are notoriously bad at accurately tracking calories, a failing that gets worse with increasing body-mass index. In other words, lean people “underestimate their daily calories by about 20 percent, while overweight people underestimate their calories by about 40 percent,” Wadden said.
Those who are trying to lose weight might try this challenging assignment: Calculate how many calories you need to maintain your weight. Just do the calculation once, or use several tools to come up with a range. If you want to lose weight, calorie counting will need to be part of your regimen for at least a few weeks. Meantime, continue following our other recommendations: Eat five servings a day of fruit and vegetables, drink enough fluids and record what you eat.
To assign calorie totals to your food intake, there are several good sources. The University of Pennsylvania uses “The Doctor’s Pocket Calorie, Fat & Carbohydrate Counter 2002 Edition,” available in print or online at www.calorieking.com. The Interactive Healthy Eating Index, on the U.S. Department of Agriculture’s Web site at www.usda.gov/cnpp/, will calculate and save data on as many as 20 days of meals.
The “cyberkitchen” at www.shapeup.org will calculate food and activity; calorie counters for hand-held computers are available at www.palmblvd.com and www.healthetech.com.
For exercise, add two more minutes of activity to your goal, taking it to 16 minutes a day. There’s no need to do those 16 minutes all at once. Fit in as many lifestyle exercises–taking the stairs, getting up to flip the TV channel instead of using the remote, walking your kids to school–as possible.
Figure out how many calories you burn by logging on to: http://cph.phenominet.com, or calculate your activity level at www.shapeup.org/fitness/assess/fset2.htm.
Stick with the program and you’ll find you’re coming closer to a healthy diet and lifestyle–and a way to monitor it.
