How to Fix a Slow Metabolism

Have you ever had one of those moments when you realize your body isn’t quite what it once was? I’m solidly in my thirties now and it seems like more and more often I realize this truth. It means a lot of things, like looking up how to fix a slow metabolism.

How to Fix a Slow Metabolism

Sometimes it’s the gray hairs creeping in. Other times it’s finding myself ready for bed at nine o’clock on a Friday night. Or remembering that I will see the effects of a burger, fries, and a milkshake later.

My metabolism sure isn’t what it once was. And metabolism is an important part of our overall health.

How to Fix a Slow Metabolism

It’s common for metabolism to slow down as we age, but there are many factors that play into our metabolic rate that we can have some control over.

Why is My Metabolism Slow?

First off, you need to identify that your metabolism is slow. You can generally tell because you feel tired or cold, or find that you’ve gained weight even though your eating habits haven’t changed.  Maybe your digestion seems a bit more “sluggish” than usual.

Why does this happen?  Why do metabolic rates slow down?

Metabolism includes all the biochemical reactions in your body that use nutrients and oxygen to create energy.  And there are lots of factors that affect how quickly (or slowly) it works, i.e. your “metabolic rate” (which is measured in calories).

But don’t worry – we know that metabolic rate is much more complicated than the old adage “calories in calories out”!  In fact, it’s so complicated I’m only going to list a few of the common things that can slow it down.

Some common reasons why metabolic rates can slow down:

  • low thyroid hormone
  • your history of dieting
  • your size and body composition
  • your activity level
  • lack of sleep

We’ll briefly touch on each one below and I’ll give you some tips on how to counteract that slowing metabolism.

Low Thyroid Hormone

If you’ve read here long at all, you know that I struggle with thyroid issues due to Hashimotos. I feel like this is the biggest contributor to my metabolism slowing down, and it could be for you too.

Your thyroid is the master controller of your metabolism.  When it produces fewer hormones your metabolism slows down.  The thyroid hormones (T3 & T4) tell the cells in your body when to use more energy and become more metabolically active.   

Ideally your thyroid should work to keep your metabolism in balance.  But there are several things that can affect it and throw it off course.  Things like autoimmune diseases and mineral deficiencies (e.g. iodine or selenium) for example.

Poor Diet

When people lose weight their metabolic rate often slows down.  This is because the body senses that food may be scarce and adapts by trying to continue all the necessary life functions with less food. 

While dieting can lead to a reduction in the amount of fat, it unfortunately can also lead to a reduction in the amount of muscle you have.  Having more muscle means a faster resting metabolic rate.

Body Size & Composition

In general, larger people have faster metabolic rates.  This is because it takes more energy to fuel a larger body than a smaller one. 

However, you probably already know that wildly gaining weight isn’t the best strategy for increasing your metabolism.

Muscles that actively move and do work need energy.  Even at rest, muscles burn more calories than fat.  This means that the amount of energy (calories) your body uses depends partly on the amount of lean muscle mass you have. 

Which leads us to…

Activity Level

Aerobic exercise temporarily increases your metabolic rate.  Your muscles are burning fuel to move and do “work.” You can tell because you’re also getting hotter – hence all the sweat during exercise.

Even little things can add up.  Walking a bit farther than you usually do, using a standing desk instead of sitting all day, or taking the stairs instead of the elevator can all contribute to more activity in your day.

Lack of Sleep

There is plenty of research that shows the influence that sleep has on your metabolic rate.  The general consensus is to aim for 7-9 hours of sleep every night.

How to Fix a Slow Metabolism

Now that you know what causes a slow metabolism, you have probably already figured out how to give your sluggish body a jump start.

Increase Exercise

Incorporate small pockets of extra movement into your day.  In addition, find a way to get regular exercise. Doctors recommend aerobic exercise 30 minutes a day, 5 times a week. Remember that this can be broken up into shorter segments too. And something is always better than nothing!


You’ll also want to do some weight training to help increase your muscle mass. While cardio is important for overall health and weight loss, building more muscle will increase your resting metabolic rate.

Weight training does not mean that you need to join a CrossFit gym and start lifting heavy, mind you. I recommend starting a slowly, usually with pilates or yoga. I am really loving my yoga practice right now, and since the exercises use your body weight you’ll build muscle without breaking the bank.

Get More Sleep

Thankfully, once you become more active, you’ll probably notice that you get tired earlier. This is a good thing!!

Try to create a routine that allows at least 7 hours of sleep every night.  If you’re struggling, be sure that you aren’t suffering from Chronic Sleep Deprivation. It’s definitely not fun!

Eat Real Food

Getting more sleep and exercising are only half the battle.

Make sure you’re eating enough food to fuel your body without overdoing it. While it differs for everyone due to age, gender, and lifestyle, you should never go below 1200 calories a day. Focusing on getting protein in can help you build more muscle as well.


Ask For Labs

If you’ve made the above changes and you still feel like your metabolism isn’t where it needs to be, it’s time to call in the professionals.

Talk with your doctor about having your thyroid hormones tested. If they’re out of range, you may need to take a synthetic thyroid hormone supplement to balance your hormones. Also, check out my Hypothyroid Protocol for tips on balancing your thyroid hormones naturally.

How do you deal with a slow metabolism?

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