You’ve probably been told that as you age, you can’t eat like your younger self.

That’s because your metabolism tends to slow with age, making it easier to add a few extra pounds and harder to lose them.

A few reasons for this include muscle loss, being less active and the natural aging of your metabolic processes.

Luckily, there are many things you can do to combat this age-related drop in metabolism.

This article explains why your metabolism slows down with age and what you can do about it.

What Is Your Metabolism?

Simply put, your metabolism is all of the chemical reactions that help keep your body alive.

It also determines how many calories you burn per day. The faster your metabolism, the more calories you burn.

The speed of your metabolism is influenced by four key factors (1):

  • Resting metabolic rate (RMR): How many calories you burn while you are resting or asleep. It is the least amount needed to keep you alive and functioning.
  • Thermic effect of food (TEF): How many calories you burn through digesting and absorbing food. TEF is usually 10% of your daily calories burned.
  • Exercise: How many calories you burn through exercise.
  • Non-exercise activity thermogenesis (NEAT): How many calories you burn through non-exercise activities, such as standing, fidgeting, washing the dishes and other household chores.

Other things that can affect your metabolism include age, height, muscle mass and hormonal factors.

Unfortunately, research shows that your metabolism slows down with age. A few reasons for this include less activity, muscle loss and the aging of your internal components.

SUMMARY:Your metabolism comprises all of the chemical reactions that help keep your body alive. Resting metabolic rate (RMR), thermic effect of food (TEF), exercise and non-exercise activity thermogenesis (NEAT) all determine your metabolic speed.

People Tend to Be Less Active With Age

Your activity levels can significantly affect the speed of your metabolism.

In fact, activity — both exercise and non-exercise activity — makes up roughly 10–30% of your calories burned daily. For very active people, this number can be as high as 50%.

Non-exercise activity thermogenesis (NEAT) is the calories burned through activity other than exercise. This includes tasks like standing, washing the dishes and other household chores.

Unfortunately, older adults are typically less active and burn fewer calories through activity.

Research shows that over a quarter of Americans aged 50–65 don’t exercise outside of work. For people over 75, this increases to over a third.

Research also shows that older adults burn roughly 29% fewer calories through NEAT.

Staying active can help prevent this drop in metabolism.

One study of 65 healthy young people (21–35 years) and older people (50–72 years) showed that regular endurance exercise prevents metabolism from slowing down with age.

SUMMARY:Research shows that people are less active with age. Being less active can significantly slow down your metabolism, as it is responsible for 10–30% of your daily calories burned.


People Tend to Lose Muscle With Age

The average adult loses 3–8% of muscle during each decade after 30.

In fact, research shows that once you reach 80, you have roughly 30% less muscle than when you were 20.

This loss of muscle with age is known as sarcopenia, and can lead to fractures, weakness and early death.

Sarcopenia also slows down your metabolism, as having more muscle increases your resting metabolism.

A study of 959 people found that people aged 70 had 20 pounds (9 kg) less muscle mass and 11% slower resting metabolism (RMR) than people aged 40.

Because muscle mass is affected by your activity level, being less active is one reason why you lose more muscle with age (13).

Other reasons include consuming fewer calories and protein, as well as a decrease in the production of hormones, such as estrogen, testosterone and growth hormone.

SUMMARY:Muscle mass increases your resting metabolism. However, people lose muscle with age due to being less active, changes in diet and a decrease in hormone production.

Metabolic Processes Slow Down With Age

How many calories you burn at rest (RMR) is determined by chemical reactions inside your body.

Two cellular components that drive these reactions are your sodium-potassium pumps and mitochondria.

The sodium-potassium pumps help generate nerve impulses and muscle and heart contractions, while the mitochondria create energy for your cells.

Research shows that both components lose efficiency with age and thus slow down your metabolism.

For instance, one study compared the rate of the sodium-potassium pumps between 27 younger men and 25 older men. The pumps were 18% slower in older adults, resulting in burning 101 fewer calories per day (16).

Another study compared changes in the mitochondria between 9 younger adults (average age of 39) and 40 older adults.

Scientists found that older adults had 20% fewer mitochondria. Additionally, their mitochondria were nearly 50% less efficient at using oxygen to create energy — a process that helps drive your metabolism.

That said, compared to both activity and muscle mass, these internal components have a lower effect on the speed of your metabolism.

SUMMARY:Cellular components like the mitochondria and sodium-potassium pumps become less efficient with age. However, the effect on metabolism is still less than muscle loss and activity.