Do you feel tired, cold or that you've gained weight. Maybe your digestion seems a bit more “sluggish”.

You may be convinced that your metabolism is slow.

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

What can slow my metabolism?

Metabolism includes all of 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.

Common reasons why metabolic rates 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 promise to give you better advice than to “eat less and exercise more”.

Low thyroid hormones

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, it should work to keep your metabolism just right.

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.

Tip: Talk with your doctor about having your thyroid hormones tested.

Your history of dieting

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 with all the necessary life functions and do it all 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. As you know more muscle means faster resting metabolic rate.

Tip: Make sure you're eating enough food to fuel your body without overdoing it.

Your size and body 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 already know that gaining weight is rarely the best strategy for increasing your metabolism.

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

Tip: Do some weight training to help increase your muscle mass.

Which leads us to...

Aerobic exercise temporarily increases your metabolic rate. Be sure to exercise regularly. — Aerobic exercise temporarily increases your metabolic rate. Be sure to exercise regularly.

Your activity level

Aerobic exercise temporarily increases your metabolic rate. Your muscles are burning fuel to move and do “work” and you can tell because you're also getting hotter.

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.

Tip: Incorporate movement into your day. Also, exercise regularly.

Lack of sleep

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

Tip: Try to create a routine that allows at least 7 hours of sleep every night.

Did you find this article helpful? Leave a comment below or send us an email at hello@inspiredlivingnutrition.com if you have any questions!

Want more? Click here to read my post on What is Metabolism?