THE DAILY DOSE

How Does Your Metabolism Change As You Age?

The metabolism is a system of chemical reactions within the body that processes food into nutrients and energy. The energy conversion that takes place is used by the most basic functions of the body, such as breathing, circulation, and digestion. The energy that is left over from the food you eat is then utilized to help you get through the day, exercise, and live your life. But as you age, the speed of your metabolism begins to slow down. There are a few reasons behind those changes, so today let’s answer the question: how does your metabolism change as you age?

Metabolism and aging

As you get older, the metabolism doesn’t always work in the same way it did when you were a child or young adult. If you’ve ever reflected that you “can’t eat the same way you did when you were younger”, you’re aware of these changes!

The slowing of the metabolism comes down to a few different factors. They include:

• The resting metabolic rate (RMR). Your RMR is the number of calories that your body needs to keep you alive. It is the energy needed to perform the most basic bodily functions.
• Thermic effect of food (TEF). This is how much energy or calories are burned away through digestion or absorption of the food you eat. Even the process of fueling your body requires energy to put the food to good use.
• Exercise. Exercise is one activity that everybody uses to burn calories, but the amount a person gets also effects their metabolism.
• Non-exercise activity thermogenesis (NEAT). This is how many calories it takes to perform basic tasks such as standing, washing dishes, or other chores.

Of course, there are other factors that affect how a person’s metabolism functions, including height, hormones, age, and the amount of muscle a person has on their body.

Why does your metabolism slow down as you age?

There are a few reasons why the metabolism will slow down with age. Some of those factors are lifestyle-related, whereas others are biologically driven. Although lifestyle factors can be changed, biological aging cannot be stopped.

Exercise and diet

One specific driver related to metabolism slowing with age is exercise. As people get older, their ability or drive to exercise becomes lower. Activity levels have such a big impact on metabolism that research has shown that exercise and non-exercise activity or movement can account for up to 30% of your daily calorie expenditure.

Although the connection between less activity and aging isn’t entirely clear, research has also found that people aged 50 and older don’t typically exercise outside of work at all. Older people also tend to eat less, which can affect the metabolism’s speed as well.

Muscle mass

A key lifestyle and biological factor that comes into play with a slowed metabolism is muscle mass. Since people are not exercising as much as they used to past a certain age, they are bound to lose some muscle. Combine that with the natural aging process and the average muscle loss that simply occurs as a result (also known as sarcopenia), and it shows exactly why the metabolism slows as a person gets older.

After a person turns 30, the average decline in muscle is anywhere from 3–8%. The reason this affects your metabolism is because muscle plays a large role in how many calories the body burns at rest (RMR). 

Hormones

Hormones have also been shown to play a role in metabolism. As the body ages, the production of certain hormones such as estrogen, testosterone, and growth hormone begins to decrease. This deduction in hormone levels also slows the metabolism.

Cellular changes

As the body ages, cellular components and chemical reactions within it begin to change. Two specific cellular components that play a role in chemical reactions that affect the metabolism are sodium-potassium pumps and mitochondria. While mitochondria is tasked with creating energy for cells, sodium-potassium pumps help with the contractions of muscle and the heart as well nerve impulses. These two components begin to lose their ability to effectively perform as the body gets older.

Although these two things contribute to the slowing of the metabolism, they account for a small part of the slowing process when compared to activity levels and the amount of muscle a person has on their body.

At what age does metabolism peak?

Although the exact age of peak metabolic function varies from person to person, research has shown that the early 20s are the age that shows the most efficient metabolism. At this age, the number of calories burned by the body while at rest are the highest. This could be due to a lot of reasons, but like all ages and metabolism, it can most likely be attributed to exercise levels and muscle mass.

Is there anything you can do to stop metabolism changing?

Although there is nothing you can do to stop the cellular process of aging, there are ways around a slowing metabolism. Keeping up with regular exercise can be a great metabolism boost. Strength training, for example, is a great way to help build and maintain muscle mass and provides the overall benefits of exercise. Studies have shown that when older people do strength training, they can increase their RMR by close to 8%.

High-intensity interval training is also a great way to help the body burn calories. This is because it has been shown to cause the body to continue burning calories for as long as 14 hours following the end of the exercise session. 

Diet can also play a role in speeding up the metabolism. By eating a diet that has a lot of protein, you can increase metabolism. This is because protein-rich foods need more energy to be digested. And it’s not always what you eat that helps metabolism, but also how much you eat. Eating too little can cause the metabolism to slow down, because by eating too little calories, the body begins to reserve energy, leading to a decreased metabolic rate.

Fighting the passage of time is always going to be a losing battle, and aging is just a natural part of life. That doesn’t mean you have to give up on a healthy and speedy metabolism. By keeping up with exercise and muscle mass, you can help to combat the natural process of metabolic slowdown.

Featured image by Abigail Keenan on Unsplash