Why metabolism slows as you age

Do you feel like you gain five pounds after eating a slice of cake? In your 20s, you could eat an entire cake and never gain an ounce. It’s not your imagination. As we age, metabolism slows and the rate at which we break down food decreases 10% each decade after 20.

Metabolism is the amount of energy (calories) your body uses to maintain itself. Your basal metabolic rate (BMR) determines how many calories you burn at rest, along with activity level and muscle-to-fat ratio.

“By the time we’re 50, there’s a 30% drop,” says Karen Andry, a licensed and registered dietitian and bariatric coordinator at Piedmont Atlanta Hospital. 

Why it’s so easy to gain weight

A slowing metabolism can lead to weight gain each year, even if you don’t eat much more than usual.

For example, eating a 500-calorie bowl of ice cream nightly adds 3,500 calories weekly, equal to about a pound of fat. Multiply that by 52 weeks a year, and one extra treat each night can lead to significant weight gain.

“It’s very simple to gain the weight, but it’s very difficult to take it off,” Andry says. 

Maintaining muscle mass is the key to preventing weight gain. However, it can be challenging because, after age 45, the average person loses about 1% of muscle mass each year.

Maintaining a healthy weight takes effort, so be mindful of what you eat every day and increase your physical activity.

Ideal body weight

How do you know if you are at your ideal weight? Medical staff typically either determine your body mass index score or use a simple formula like this one:

• Female – 5’0” = 100 lbs
• Female – 5’1” = 105 lbs
• Female – 5’2” = 110 lbs
• Female – 5’3” = 115 lbs.
• Female – 5’4” = 120 lbs.
• Female – 5’5” = 125 lbs.

“We use the Metropolitan Life Insurance tables for ideal body weight from years ago,” Andry says. “They’re not really very realistic; however, they’re used across the board, so you can compare apples to apples.”

Because everyone's lifestyle and risk factors are unique, talk with your primary care physician to determine your ideal weight. Click here to find a doctor near you.

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