Why we burn fewer calories as we age – 10/13/2023 – Balance

Your body’s need for fuel changes as you age. Therefore, your eating habits must also change.

You can think of burning calories as “Step 1 of being alive,” says Herman Pontzer, professor of evolutionary anthropology at Duke University. Food provides your body with the fuel it needs to stay healthy, he explains.

Your age — among several other factors — can have a big effect on the amount of calories you need to maintain your weight and basic body functions, Pontzer and other experts said.

Here’s what you need to know.

HOW YOUR AGE AFFECTS YOUR CALORIC EXPENDITURE

Your body size is the most important factor when it comes to your calorie needs, says Pontzer. “The bigger you are, the more calories you need.”

But your stage of life is also crucial, he adds.

Babies and children, for example, need fewer calories than adults simply because they are smaller. But when you calculate how many calories they burn relative to their body size, it’s actually more than adults because they’re growing and developing, says Pontzer.

Being more physically active also increases the number of calories you burn, says Anna Maria Siega-Riz, professor of nutrition and dean of the School of Public Health and Health Sciences at the University of Massachusetts Amherst. She was the lead author of a 2023 report from the National Academies of Sciences, Engineering, and Medicine that estimated the calorie needs of people in the United States and Canada.

According to this report, a 40-year-old, 200 lb (about 90 kg) inactive man would need about 2,700 kcal per day to maintain his weight and basic bodily functions. But if he were an athlete training a few hours a day, he would need about 3,500 kcal a day.

The same report estimated that starting at age 19, calorie requirements “decrease” a little each year — about 11 kcal annually for men and seven for women, says Susan Roberts, associate deputy director for fundamental research at the School of Dartmouth Medicine Geisel.

A 170 lb (about 70 kg) woman who walks 60 to 80 minutes a day, for example, would need 2,450 calories a day by age 20. At age 60, however, this would drop to 2,150 and at age 80 to 2,000.

This age-related decrease in calorie burn is usually most noticeable at age 60 or older, says Roberts, possibly manifesting itself in weight gain or a less robust appetite. As you age, you tend to lose muscle and gain fat, which burns fewer calories, she says. And your brain — the body’s most metabolically active tissue — naturally shrinks in size and requires less energy, she adds.

It’s also common for people to become less physically active as they age, further reducing the number of calories they burn daily, says Siega-Riz.

You can estimate your own calorie needs using an online calculator. Just keep in mind that these calculators can only give you a general picture of what you should consume. Your actual needs will vary depending on your daily activities, genetics and other factors, says Siega-Riz.

If you’re wondering if you’re consuming the right amount, the best way to check is to weigh yourself every once in a while, recommends Siega-Riz. If your weight is relatively stable, then you are eating an appropriate amount of calories.

But for some people, too much focus on the scale can create or worsen anxieties about food and weight, says Siega-Riz, so weigh yourself only as often as you feel comfortable.

WHAT THIS MEANS FOR YOUR FOOD

The good news is that you probably won’t need to count calories as you get older, because your appetite should naturally decrease to meet your needs, says Pontzer.

But as you age, it’s important to make sure you’re getting the right balance of nutrients, says Roberts.

For example, research suggests that starting at age 50, your body needs more certain nutrients, such as calcium, vitamin B6, vitamin D, and protein, even though you’re consuming fewer daily calories overall.

Because of this, says Siega-Riz, you’ll need to dedicate more of your daily calorie budget to foods that provide you with the most nutrients, such as fruits, vegetables, whole grains, and lean sources of protein.

Roberts agreed. When you’re in your 20s and 30s, she said you “may still have calories left over for chocolate, a beer or a piece of cake.” But if you’re 80 and only consuming about 1,500 kcal a day, there’s less room for treats, she says.

The expert thinks it’s prudent for seniors to take a multivitamin supplement to help fill any nutritional gaps. But even so, a good diet is still necessary to ensure you’re getting other important nutrients, like protein, fiber, and healthy plant compounds, she says.