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Evidence Based

Why Your Metabolism Slows Down With Age

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.

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What Is Your Metabolism?

Middle Aged Couple During Fall

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 (1).

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 (2, 3).

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% (4).

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 (5).

Research also shows that older adults burn roughly 29% fewer calories through NEAT (6).

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 (7).

Summary: Research shows that people become 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.
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People Tend to Lose Muscle With Age

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

In fact, research shows that once you reach 80, you have roughly 30% less muscle than when you were 20 (9).

This loss of muscle with age is known as sarcopenia, and can lead to fractures, weakness and early death (10).

Sarcopenia also slows down your metabolism, as having more muscle increases your resting metabolism (11).

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 (12).

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 (13, 14).

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 (15, 16).

The sodium-potassium pumps help generate nerve impulses and muscle and heart contractions, while the mitochondria create energy for your cells (17, 18, 19).

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 (average age 69) (20).

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.
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How Much Does the Metabolism Slow Down With Age?

The speed of your metabolism is affected by your activity levels, muscle mass and several other factors. As a result, metabolic speed varies from person to person.

For instance, one study compared the RMR of three groups of people: those aged 20–34, 60–74 and over 90. Compared to the youngest group, people aged 60–74 burned roughly 122 fewer calories, while people over 90 burned around 422 fewer calories.

However, after accounting for differences in gender, muscle and fat, scientists found that the people aged 60–74 burned only 24 fewer calories, while those over 90 burned 53 fewer calories on average daily.

This shows that maintaining muscle is incredibly important as you age (21).

Another study followed 516 older adults (aged 60 plus) for twelve years to see how much their metabolism fell per decade. After accounting for muscle and fat differences, per decade, women burned 20 fewer calories at rest, while men burned 70 fewer calories.

Interestingly, both men and women were also less active and burned 115 fewer calories through activity per decade. This shows that staying active as you age is crucial to maintaining metabolism (3).

Nevertheless, one study found no difference in RMR between women of all ages. However, the oldest group of people in the study lived very long (over 95 years), and it is thought their higher metabolisms are the reason why (22).

In short, research seems to show that being less active and losing muscle has the greatest negative effect on your metabolism.

Summary: Research shows that losing muscle and being less active are the biggest reasons why your metabolism slows down with age. Compared to these two factors, everything else only has a minor effect.
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How Can You Prevent Your Metabolism Slowing Down With Age?

Although the metabolism typically slows down with age, there are many things you can do fight this. Here are six ways you can combat the effects of aging on your metabolism.

1. Try Resistance Training

Resistance training, or weight lifting, is great for preventing a slowing metabolism.

It offers the benefits of exercise while preserving muscle mass — two factors that affect the speed of your metabolism.

One study with 13 healthy men aged 50–65 found that 16 weeks of resistance training three times weekly increased their RMR by 7.7% (23).

Another study with 15 people aged 61–77 found that half a year of resistance training three times weekly increased RMR by 6.8% (24).

2. Try High-Intensity Interval Training

High-intensity interval training (HIIT) can help prevent a slowing metabolism. It is a training technique that alternates between intense anaerobic exercise with short periods of rest.

HIIT also continues to burn calories long after you finish exercising. This is called the “afterburn effect.” It occurs because your muscles need to use more energy to recover after exercise (25, 26).

In fact, research has shown that HIIT can burn up to 190 calories over 14 hours after exercising (26).

Research also shows that HIIT can help your body build and preserve muscle mass with age (27).

3. Get Plenty of Sleep

Research shows a lack of sleep can slow down your metabolism. Fortunately, a good night’s rest can reverse this effect (28).

One study found that 4 hours of sleep reduced metabolism by 2.6% compared to 10 hours of sleep. Fortunately, a night of long sleep (12 hours) helped restore metabolism (29).

It also seems that poor sleep may increase muscle loss. Since muscle influences your RMR, losing muscle can slow down your metabolism (30).

If you struggle to fall asleep, try unplugging from technology at least one hour before bed. Alternatively, try a sleep supplement.

4. Eat More Protein-Rich Foods

Eating more protein-rich foods can help fight a slowing metabolism.

That’s because your body burns more calories while consuming, digesting and absorbing protein-rich foods. This is known as the thermic effect of food (TEF). Protein-rich foods have a higher TEF than carb- and fat-rich foods (31).

In fact, studies have shown that consuming 25–30% of your calories from protein can boost your metabolism by up to 80–100 calories per day, compared to lower protein diets (32).

Protein is also essential to fight sarcopenia. Thus, a protein-rich diet can fight an aging metabolism by preserving muscle (33).

A simple way to eat more protein daily is to have a source of protein at every meal.

5. Make Sure You Eat Enough Food

A low-calorie diet can slow down your metabolism by switching your body into “starvation mode” (34).

While dieting has its benefits when you’re younger, maintaining muscle mass is more important with age (35).

Older adults also tend to have a lower appetite, which may decrease calorie intake and slow metabolism (36).

If you struggle to eat enough calories, try eating smaller portions more frequently. It is also great to have high-calorie snacks like cheese and nuts handy.

6. Drink Green Tea

Green tea can increase your metabolism by 4–5% (37).

This is because green tea contains caffeine and plant compounds, which have been shown to increase your resting metabolism (38).

A study in 10 healthy men found that drinking green tea three times daily increased their metabolism by 4% over 24 hours (39).

Summary: Although your metabolism slows down with age, there are many ways to combat this. This includes resistance training, high-intensity training, getting plenty of rest, eating enough protein and calories and drinking green tea.
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The Bottom Line

Research shows that your metabolism tends to slow down with age.

Being less active, losing muscle mass and the aging of your internal components all contribute to a sluggish metabolism.

Fortunately, there are plenty of ways to fight aging from slowing down your metabolism.

This includes weight lifting, high-intensity interval training, eating enough calories and protein, getting plenty of sleep and drinking green tea.

Try adding a few of these strategies into your daily routine to help keep your metabolism fast and even give it a boost.

An evidence-based article from our experts at Authority Nutrition.
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