Q: I’m in my 50s, and I’ve heard that it’s normal to burn fewer calories as I get older. Is this true?

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

Your age — among several other factors — can have a big effect on how many calories you need to maintain your body’s weight and basic functions, Dr. Pontzer and other experts said.

Here’s what to know.

How your age affects the calories you burn

The size of your body is the most important factor that affects your calorie requirements, Dr. Pontzer said. “The bigger you are, the more calories you need.”

But your life stage is also crucial, he added.

Babies and children, for example, require fewer calories than adults simply because they are smaller. But when you calculate how many calories they use relative to their body size, it’s actually more than what adults use because they are growing and developing, Dr. Pontzer said.

Being more physically active also increases the number of calories you burn, said Anna Maria Siega-Riz, a nutrition professor and the 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 that report, an inactive, 200-pound, 40-year-old man would need about 2,700 calories per day to maintain his weight and basic bodily functions. But if he were an athlete training for a couple of hours each day, he would need about 3,500 calories per day.

The same report estimated that starting around age 19, calorie requirements “drift down” a bit each year — to the tune of about 11 calories annually for men and seven for women, said Susan Roberts, a senior associate dean of foundational research at the Dartmouth Geisel School of Medicine.

A 170-pound woman who walks for 60 to 80 minutes each day, for example, would need 2,450 calories per day at age 20 — at age 60, however, that would drop to 2,150, and at 80 it would be 2,000.

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

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

You can estimate your own calorie requirements using an online calculator. Just keep in mind that such calculators can provide only a general picture of what you should consume. Your actual needs will vary according to your daily activities, genetics and other factors, Dr. Siega-Riz said.

If you’re wondering whether you’re consuming the right amount, the best way to check is to weigh yourself every so often, Dr. Siega-Riz said. If your weight is relatively stable, then you’re eating an appropriate number of calories.

But for some people, a hyper-focus on the scale can create or worsen anxieties about food and weight, Dr. Siega-Riz said, so weigh yourself only as often as you’re comfortable.

What burning fewer calories means for your eating habits

The good news is that you probably won’t need to do much calorie counting as you age, because your appetite should naturally ebb to match your needs, Dr. Pontzer said.

But as you get older, it’s important to make sure you’re getting the right balance of nutrients, Dr. Roberts said.

For instance, research suggests that beginning in your 50s, your body needs more of certain nutrients such as calcium, vitamin B6, vitamin D and protein, even though you’re likely eating fewer daily calories overall.

Because of that, Dr. Siega-Riz said, you’ll need to dedicate more of your daily calorie budget to foods that give you a bigger bang for your buck nutrient-wise, like fruits, vegetables, whole grains and lean sources of protein.

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

Dr. Roberts thinks it’s wise for older adults to take a multivitamin supplement to help fill in any nutritional gaps. But even then, a good diet is still necessary to ensure you’re getting other important nutrients like protein, fiber and healthful plant-based compounds, she said.

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