By Brierley Wright, M.S., R.D., January/February 2008
If you’ve celebrated your fortieth birthday, you probably suspect that your metabolism isn’t quite what it used to be. The bad news is you’re right: calorie burn does decrease with age. But there’s also good news: you’re probably burning more than you think. New research in the American Journal of Clinical Nutrition reveals just how many calories, on average, men and women in their forties, fifties and sixties burn each day. Drum roll… please! According to the study, men aged 40 to 69 expend about 2,900 calories. Women of the same age burn 2,300 calories daily. (These averages vary based on a person’s height, weight and activity.)
These numbers may sound surprisingly high if you compare them to a Nutrition Facts label, which implies the average person needs about 2,000 calories daily. They may seem downright decadent to one who has followed dieting plans where daily calorie caps are set at 1,200 or 1,500 calories. But they’re good approximations for how much energy people of this age group are expending. Janet Tooze, Ph.D., lead researcher and assistant professor at Wake Forest University School of Medicine, and her colleagues used doubly labeled water, a tool that measures carbon dioxide production (an actual marker of calories burned), to determine the energy expenditure of the 450 middle-age men and women in the study.
The reason people of all ages may assume they’re burning less than they really are may be that they think they’re eating fewer calories than they are actually consuming. When it comes to estimating calories, says Tooze, “generally people underreport [their calorie intake] by about one-third.”
As for that age-related decrease in metabolism, it’s probably most marked in one’s sixties and beyond. “We found—and so have other studies—that there is a decrease in muscle in your sixties, particularly in women,” says Tooze. Since muscle is a calorie-burning powerhouse, muscle loss equals fewer calories burned. In this study, daily caloric burn of women and men in their early fifties was 4 and 8 percent higher, respectively, than that of people in their late sixties. (Men in their sixties still burned about 2,700 calories; women, 2,200.)
Bottom line: While the aging metabolism situation isn’t as bleak as you might assume, you do need to be more vigilant to maintain your weight as you age. “You will lose muscle as you grow older, but with strengthening exercises you can preserve a lot of it,” says EatingWell advisor Miriam Nelson, Ph.D., director of Tufts University’s John Hancock Center for Physical Activity and Nutrition. Assess how accurate you are in estimating the calories you consume by gauging changes in your weight. “If you’re weight-stable, go with what you’re doing,” says Nelson.
If you’re gaining, start making changes. The EatingWell Diet, a 28-day menu plan and self-tracking program, helps you lose weight by balancing calories in with calories out. For tips from the book and worksheets to track your eating and activity, go to eatingwell.com/diet.