In the world of diet, health, and fitness, you can hear and talk about metabolism everyday. People talk about slow metabolism, fast metabolism, lazy metabolism, and more. So what metabolism really is? And how come as an infant it seems like we all have the same rate of metabolism, but as we grow older it tends to change? Is metabolism genetic or environment has an effect in it? Do we have a say in our metabolic rate? These are all the questions that have been lingering in my mind and everyone who I talked to tends to have an opinion about the M word, but lets see what science has to say about it.

In a separate blog post I talked about what metabolism means and how to boost it. In this blog post, lets look at the factors that determine the speed of our metabolism.

What determines the speed of your metabolism?

The rate of  metabolism is based on multiple factors such as body composition, age, weight, gender,  and endocrine glands. Lets look at these factors individually and see if we can control them or not.

Body composition:

Body composition is how much muscle vs fat you have in your body. The more muscle the higher your metabolism. So as you can see we have a say in this one. By doing strength and aerobic training you will be able to gain muscle. The more muscle you have the higher your metabolism. When it comes to the muscles the old saying “use it or loose it” is so true. If you don’t use your muscles, you will loose them.

I believe most of us have control over our body composition, we just need to decide.


We all have heard that our metabolisms will slow down as we age, but why?

Yes we have no control over our age, we get older every day, but as studies have shown, aging and lifestyle choices that we make go hand in hand when it comes to the rate of our metabolism. The skeletal muscle is the largest organ that consumes energy in a normal human body, as we age the volume of our skeletal muscle decreases and it gives its place to fat tissue. (1) The reality is as we age, we tend to get less physically active for various reasons, and this change in physical activity is one of the reasons behind slowing metabolic rate.

Now do you think you can control this or not?

Age is just a number, so don’t let it stop you from feeling and looking the way that you like.


Weight and body composition go hand in hand. Over weight people, who have more fat than muscle in their body tend to have lower metabolic rate. And the leaner people with more muscle have higher metabolism. This is simply because muscle consumes more energy than fat.


Yes it is true, unfortunately, us women tend to have lower metabolic rate than men. Studies have shown that Resting Metabolic Rate (RMR) is lower in women than men independent of their body composition and aerobic fitness, but why? Unfortunately, I could not find any scientific proven reason to answer this question. Most experts suggest that it is because Women have more adipose tissue than males, but the study above showed that females tend to have lower RMR than males with the same body composition. So my guess would be it has something to do with our hormones!!!!!!! I have to dig dipper into this one.

Endocrine glands:

The endocrine system plays a vital role in the metabolism of the body via several endocrine glands that are responsible for the secretion of endocrine hormones. Of particular importance in the function of the endocrine system and metabolism of the body are two organs: the thyroid and the pancreas.

The thyroid gland is comprised of two lobes which are connected by the isthmus, a small stalk. The role of the thyroid gland in the metabolism of the body is due chiefly to the effects of two hormones secreted by the thyroid gland. These hormones are thyroxine (T4) and triiodothyronine (T3). The two hormones are synthesized in the thyroid by combining iodine with tyrosine and are secreted into the blood as a plasma globulin complex. They are also responsible for the proper utilization of energy, regulation of body growth, metabolic rate and development of bones and skeletal muscles.

as a rule of thumb the more active your thyroid glands, the more energy you consume and higher your metabolic rate and the less active they are the less energy you consume and lower your metabolic rate. So if you think you are suffering from slow metabolism, maybe it is time to visit your doctor and check on your thyroid hormones to make sure they are working properly.

The pancreas is another important component of the endocrine system and metabolism of the body. This is due to the synthesis of two important endocrine hormones: insulin and glucagon. Insulin is vital to energy regulation and glucose metabolism in the body. Insulin stimulates cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle. Glucagon on the other hand raises blood glucose levels. The pancreas releases glucagon when blood glucose levels fall too low.  Basically insulin and glucagon work in what’s called a negative feedback loop. During this process, one event triggers another, which triggers another, and so on, to keep your blood sugar levels balanced.

Here is what happens as we gain weight and become overweight, our bodies produces more insulin than normal. This is true about people who suffer from diabetes as well. The reason is because in overweight or diabetic people, body can’t use its insulin effectively enough, so it produces more insulin. The more insulin the more chances you gain weight.

So if you are insulin sensitive, or if you have been gaining weight for no reason, stop blaming your low metabolism and give your health care provider a visit to see what is happening with your insulin levels.

As you can see, you have control over your hormones, you just need to know what is going on with them and get them under control. Sometimes you can do this naturally by changing your lifestyle and your diet. Sometimes it is more complicated, and you might have to take medication, but be aware of the side effects of any medication that you choose to take and always, always get second or third opinion, it doesn’t hurt.

Bottom line:

As you can see from all the factors that determine your metabolic rate, there is only one that  you have no control over, or at least as of today you have no control over, and that is your gender. Age, body composition, hormones, and weight are all under your control. yes you read it right, you have control over age. you might not be able to change the date on your birth certificate, but you have full control over how quickly or slowly you age by choosing the right lifestyle. In short the lifestyle that you are looking for is a lifestyle away from processed foods, stress, inflammation and full of activity and smile. So smile more.

Stay happy and healthy


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