You’ve probably been told --and/or noticed--that as you age, you can’t eat like you did when you were younger.  You may have started to put on pounds in your forties or fifties.  And if you look around I’m sure you’ll notice most people not getting any slimmer as they get older.  Why is this?

 
The short answer is that our metabolism tends to slow with age, making it easier to add a few extra pounds and harder to lose them.

I know this can feel disheartening.  But don’t despair! This age-related drop in metabolism is not inevitable!  In fact in primitive cultures, people tend to lose weight as they age, not gain it.  The age related weight gain we see around us is culturally influenced.  There are things you can do to counteract it and keep yourself lean and healthy through your later years.

What Is “Metabolism”?

Simply put, your metabolism is a sum of the chemical reactions that help keep your body alive.  It determines how much energy (measured in calories) you burn per day.  The faster your metabolism, the more you burn.  Unless you’ve been living on a desert island for the past 50 years, you’ve probably heard the old “calories in/calories out” mantra --that in order to lose weight you have to burn more calories than you eat.  And while this is technically true, it’s a lot more complicated than that.  Most people know about “exercise” (I use quotes here because there are a lot of different ways to move!) as a key way to burn energy, but the speed of your metabolism is in fact influenced by a lot more than just exercise. Below is a list of other factors in the metabolism equation:

Other Factors In The Metabolism Equation:

1. Resting metabolic rate (RMR): The number of calories you burn while you are resting or asleep.

2. Thermic effect of food (TEF): The energy you burn through digesting and absorbing food (TEF is on average about 10% of your daily calories).  Different foods have different thermic effects. For example, breaking down and absorbing protein requires 20-35% of the energy consumed, whereas digesting carbohydrates and fats require 5-15%.

3. Non-exercise activity thermogenesis (NEAT): This is a fancy name for the energy you burn through non-exercise activities, such as standing, walking, fidgeting, housework, fidgeting, gardening, carrying groceries, playing with your kids/pets.  Increased daily movement is something we tend to discount, but it adds up and can have a huge impact on calories burned.  

Now let’s look at how these factor into why we tend to gain weight as we age.  Again, there are several things at play here:

Why We Tend To Gain Weight As We Age

One of biggest reasons our metabolism tends to slow down with age is that we are often less active as we get older.  Our activity levels significantly affect the speed of our metabolism.  Activity — including exercise and non-exercise activity — makes up roughly 10–30% of our calories burned daily. For very active people, this number can be as high as 50%.  So a drop in activity levels translates to a drop in metabolic rate.

Another major factor is that we tend to lose muscle with age.  The average adult loses 3–8% of muscle each decade after age 30.  In fact, research shows that once you reach 80, you have roughly 30% less muscle than when you were 20!  Since having more muscle increases your resting metabolism, this age-related loss of muscle slows down your metabolism and can lead to weight gain.  

There are several reasons we lose muscle as we age including:

  • consuming fewer calories and protein
  • a decrease in the production of hormones, such as estrogen, testosterone and growth hormone
  • decreased activity level

A third factor affecting our metabolism is that our cellular metabolic processes slow down with age.  The amount of energy we burn at rest (RMR) is determined by chemical reactions that occur inside our cells.  Research shows that the number of mitochondria--the fuel burners of our cells-- decreases and that they lose efficiency with age.  That said, this effect on metabolism is smaller than the effects of decreased activity levels and muscle mass.

What about menopause and hormonal changes?  Women do tend to put on a pound a year in their 40s and 50s, but researchers believe it’s more likely due to a drop in activity and muscle mass rather than hormones.  However, hormonal changes can shift your body composition, so as you age, any pounds you do gain tend to go straight to your middle.

How Can You Prevent Your Metabolism Slowing Down With Age?

Although for most people in industrial societies metabolism typically slows down with age, please don’t fall into the trap of believing this is your destiny! We see it around us everywhere-- we watch our friends and relatives go through it, so we assume weight gain is just part of aging.  It is not.   

Although our bodies do go through some metabolic changes as we age, our reduced metabolism seems to be more a factor of our change in lifestyle factors--which show up as changes in body composition-- than aging itself.  There are many things you can do prevent metabolic slow down and the weight gain that accompanies it. Here are a few strategies:


1. Non-Exercise Activity

Increasing non-exercise activities such as standing, walking, fidgeting, housework, gardening, carrying groceries, or playing with your kids or pets is a great place to start.  Doing more of these activities can make a huge difference in the number of calories you burn each day without working hard or even thinking about it. 

Limiting sitting time by simply finding times to stand rather than sit can have a huge impact on your health. Many people have moved toward standing desks for this reason. If you watch tv you can also try using a treadmill while watching. (If you spend a lot of time watching tv, this one could be a game changer.)

2. Exercise

Any exercise you do can be beneficial, especially if you're having fun while doing it. But a few types can be especially helpful.  Resistance training (or weight lifting) is great for increasing metabolic rate because it preserves or increases muscle mass in addition to providing hormonal benefits.

High intensity interval training (aka HIIT) is another exercise technique that preserves muscle mass.  It alternates between short, intense anaerobic exercise with periods of rest and recovery.

3. Sleep

Research shows a lack of sleep can slow down your metabolism. Fortunately, getting back on track with sleep can reverse these effects.  Try setting up a regular sleep schedule (going to bed at roughly the same time each night) and getting between 7-9 hours of sleep per night.


4. Eat Enough Quality Food, Especially Protein

A low-calorie diet can slow down your metabolism by switching your body into “starvation mode.” This can end up backfiring and leading to weight gain.  It’s important to eat enough food, making sure to eat quality, nutrient dense food--while leaving out less nutrient dense foods.

Eating more protein rich foods can help prevent metabolic slow-down. 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.

There are a couple of reasons for this.  One is that consuming protein replaces the protein your body breaks down on a regular basis, putting you in a protein balance and preserving muscle.  Also, your body burns more calories while consuming, digesting and absorbing protein than it does for other foods (remember TEF?)  

5. Green Tea

Some studies show green tea can increase your metabolism by 4–5% and help reverse the effects of age-related metabolic slow down-- due to the combination of catechins (antioxidant compounds) and caffeine.

In Summary...

Research shows that our metabolism tends to slow down with age.  The biggest reasons for this are that with typical aging, we tend to become less active and lose muscle mass. I say "typical" to make clear that this occurs in most people in our culture, but is absolutely avoidable! Our perception of aging is largely based on how the people we see around us age rather than how we are capable of aging. Keep in mind: because it is common does not mean it is normal.  

Fortunately, there are ways to avoid weight gain due to age-related metabolic slow-down.  Try adding a few of these strategies into your daily routine to help preserve muscle, decrease fat accumulation, and keep your metabolism humming regardless of your age.

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