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Hormones that Impact Metabolism

There are literally dozens of hormones that influence your metabolism.  In this article I’ve focused on the hormones that have the most impact on your body weight.  Some may be familiar, some may not but as you read through you will start to understand the impact that one hormone has upon another and how easy it is to upset the hormonal apple cart.

I’ve detailed the role each hormone plays in metabolic function, hunger, body fat, energy levels and other aspects of general health.  Once you know what’s happening to your metabolism and why, you’ll see why achieving hormonal balance is the best way to achieve permanent weight loss.


Insulin affects every cell and every organ in the body and when it comes to food this hormone stands head and shoulders above all the rest.  Problems with insulin are the root cause of serious medical conditions such as diabetes and metabolic syndrome and have been linked to other medical problems such as heart attacks, strokes, hypertension and even early death.

Where is insulin made?  The pancreas which is positioned just behind your stomach.

How does insulin effect your metabolism?   Insulin’s main role is to control the amount of glucose (sugar) in your blood.  As your body starts to digest and break down the food you have eaten, carbohydrates (broken down to their most basic form) are transported in the blood to the liver where they are converted to glucose.  Glucose is detected by the beta-cells of the pancreas which responds by pumping out insulin.  Insulin’s job is to carry the glucose to the muscle cells to be used as energy and also to the fat cells where it can be stored as fuel to be used later.

What causes insulin imbalance?   Problems occur when your body has to create too much insulin.  The most common cause? Eating too many of the wrong kind of carbohydrates; refined carbs such as white bread, pasta, cakes, cookies etc.  These foods increase your blood sugar levels dramatically and to cope with this your pancreas increases the amount of insulin it creates. 

For example, lets say you eat a bag of M&M’s on an empty stomach.  You get a huge surge of sugar in the blood so insulin works twice as hard to remove the sugar from your blood.  The trouble is that the insulin is over-efficient and leaves too little glucose circulating in your bloodstream.  Your blood sugar levels are now too low and you experience the post-sugar crash, you feel  tired and hungry again and crave (and probably eat) more carbs. 

However, your liver and muscle cells have taken up all the glucose they needed from the M&M’s you ate earlier, so your fat cells happily take up glucose from your latest snack, essentially turning it into fat.  Unfortunately, the excess insulin now circulating your bloodstream will prevent your body from using fat stores as fuel.

If you repeat this cycle often enough, your pancreas will overcompensate and start to produce more and more insulin.  Eventually the hormone receptors in your cells stop working properly and become insulin resistant.

Everyone who is overweight has some degree of insulin resistance – the heavier you are the more insulin resistance you have.

Insulin resistance is a precursor to Type 2 diabetes, is common among people with metabolic syndrome and is linked to a variety of medical complications such as:

  • High blood pressure
  • Insomnia
  • Polycystic Ovary Syndrome
  • Fatty liver disease
  • Cardiovascular disease

Growth Hormone

Growth Hormone is an anabolic hormone – it builds muscle.  It reduces the amount of fat in the body, increases muscle mass, improves heart function, strengthens bones, helps wounds heal faster and even improves your mood.

Where is Growth Hormone made?  The pituitary gland found in the brain.

How Growth Hormone impacts metabolism  Growth hormone increases your lean muscle mass which raises your resting metabolic rate which means your body becomes more efficient at burning fat.  And growth hormone helps further by stimulating your fat cells to break down fat making it burnable as fuel.

What causes Growth Hormone imbalance?  Stress is a major factor in growth hormone resistance.  It can be any kind of stress: physical, emotional or as a result of a disease such as diabetes.  Not getting enough sleep can alsoaffect your growth hormone levels.  Growth hormones are released in pulses several times a day but the largest pulse happens at night during our deepest stage of sleep.  If you regularly get less than 7 hours of sleep a night or have your sleep interrupted your growth hormone levels could fall.

Leptin resistance also lowers growth hormone levels and vice versa.

Another cause of growth hormone deficiency is aging.  Our growth hormone levels usually peak during puberty and then gradually decline so by the time we are 30-40 our levels are half what they were at their peak.



Leptin is the hormone that tells your brain that your stomach is full.

Where is Leptin made?  In our fat cells.  Before it’s discovery in 1994 scientists used to believe that our fat cells were just big blobs of gloop, only used to store excess calories in our bodies.  Now we know that fat cells are part of the endocrine system and many more fat cell hormones have been discovered.

How Leptin impacts metabolism  When you eat a meal the fat cells in your body produce leptin.  It travels toyour brain where it bonds with leptin receptors.  These receptors release proteins that control the signalling system that switches our appetite on and off and your body gets the message that you are no longer hungry.

What causes leptin imbalance?  As you gain weight your leptin levels start to increase.  You may think that higher leptin levels would be a good think but, similar to what happens with insulin resistance, excess levels are a real problem.  As your body produces more and more leptin so the receptors for leptin become worn out and can no longer bond with the hormone.  This means that the whole system for switching off your appetite also fails, you remain hungry and your metabolism slows down.

Leptin resistance and insulin resistance go hand in hand; start to lose some weight and your body will become more sensitive to insulin, decreasing leptin resistance.


Thyroid problems are very common and millions of people suffer because their thyroid levels are too low.  However, it’s estimated that about half of those with thyroid dysfunction don’t even know about it because the wide variety of symptoms make thyroid disease very difficult to pin down.

Where are thyroid hormones made? Your thyroid gland which is a small, butterfly-shaped organ found at the base of your throat.

How thyroid hormones affect your metabolism  Thyroid hormones are critical for a huge range of functions in your body. They help regulate your body temperature, metabolism and help to maintain psychological well-being, appetite, energy levels, sex drive and mood.  There are two types of thyroid hormones, T3 and T4, and a healthy thyroid gland will produce about 80% T4 and 20% T3.  T4 is considered an inactive hormone.  In order for it to become activated one of the iodine molecules on the outer ring must be removed by special enzymes.  Problems with removing the iodine molecule or even removing the wrong iodine molecule can lead to thyroid dysfunction.

What causes thyroid hormone imbalance? Many factors will impact the efficiency of your body to convert T4 to T3; illness, stress, pregnancy, menopause, extreme dieting, environmental toxins.  Thyroid disease can also be genetic.  With Hashimoto’s disease, the immune system causes chronic inflammation in the thyroid gland.  It’s a hereditary disease and is seven times more likely to affect women than men.

An underactive thyroid can make you feel sluggish and your head feel ‘foggy’.  Your energy levels drop and you may start to gain weight.  Other symptoms include:

  • Confusion and forgetfulness
  • Depression
  • High blood pressure
  • Intolerance of cold
  • Heavy, prolonged periods

As I mentioned earlier, diagnosing thyroid dysfunction can be difficult because there are so many symptoms that are similar to other conditions.  I strongly recommend you visit your doctor and ask to have your thyroid tested if you suffer from any of the symptoms listed.

Cortisol is one of our fight-or-flight hormones (adrenalin is another) which help us deal with stressful situations.  While the effects of our fight-or-flight hormones may be fleeting, cortisol tends to stick around and as one of its functions is to help control body fat in terms of the amount we store and where it is distributed, it can have a huge impact on our weight.

Where is cortisol made?  In the adrenal glands which are found on top of the kidneys.

How cortisol affects your metabolism  High cortisol levels can have an incredible impact on your health and weight.  Cortisol is a counter-insulin hormone which means it increases insulin resistance and causes the accumulation of fat in the abdominal region.  Cortisol excess lowers the levels of your muscle building hormones, inhibits thyroid function and increases your appetite.  Too much cortisol also causes the breakdown

of vital tissue such as muscle, bones, tendons, ligaments and skin.  Cortisol will also magnify the effect of insulin resistance and can even lead to diabetes.

What causes cortisol imbalance?  Chronic stress causes our adrenal glands to work overtime which leads to cortisol excess.  We need cortisol to help us deal with the stress of everyday life but if there is too much stress our bodies can’t keep up with the constant surges of cortisol.  Stress comes in many forms; constant worrying, excess weight, yo-yo dieting, excessive exercising, chronic illness – any of these stressors can cause the adrenal glands to go into overdrive.

Estrogen and Progesterone

Men and women both produce estrogen and progesterone but for women the role of estrogen is incredibly powerful.  Estrogen is the name given to a group of hormones.  These are the hormones that transform us from girls into women – they shape our hips and breasts, help to control menstruation and pregnancy and make us feel feminine.  But that’s not all.  Estrogens also help to regulate body temperature, keep your moods positive and also help maintain your memory, concentration and bone density.  Progesterone plays a big part in protecting pregnancy and promoting breastfeeding but it also works to counter the growth effects of estrogen.  If estrogen and progesterone are not balance we may develop problems such as fibroids, heavy bleeding, endometriosis and breast cysts.

Where are estrogen and progesterone made?  In women they are produced in the ovaries, adrenal gland, fat tissue and placenta.  In men they are produced in the testes and adrenal glands.

How do estrogen and progesterone impact metabolism?  The three main estrogen hormones are estradiol, estrone and estriol.  Before we reach menopause most of the estrogen made by our bodies is estradiol which is produced in the ovaries.  This is the estrogen of youth!  It smooths our skin, protects our brain, heart and bones and regulates our menstrual cycle.  It also lowers insulin to keep our moods stable and energy levels high while regulating hunger by creating the same satisfied feeling that comes from serotonin.  Estradiol also puts fat on your bum, hips and thighs and although none of us want excessive fat in these areas, the fat stored here will help your insulin response and is not as detrimental to your health as fat stored around the middle.

As we get older and our bodies prepare to go through the menopause, our ovaries start to shut down and our levels of estradiol decrease.  Then estrone becomes our main estrogen which is bad news.  Estrone is produced in our fat cells and adrenal glands.  Before menopause it is easily converted to estradiol but after menopause it remains as estrone.  Estrone will shift the fat from your lower body to your belly.  As your ovaries start to produce less and less estrogen so your body wants to hang on to other estrogen making areas of the body – namely fat.  You then get into a vicious cycle; more estrone = more belly fat, more belly fat = more estrone.

Unfortunately the estrogen vicious cycle doesn’t stop there.  Insulin increases circulating levels of estrogen and estrogen increases insulin resistance..

Progesterone helps to balance estrogen but our progesterone levels drop dramatically at menopause so this can magnify the issue.

(Estriol isn’t nearly as prevalent as estradiol or estrone as it is produced almost exclusively during pregnancy).

What causes estrogen and progesterone imbalance?  As you’ve already read, our natural levels of these hormones start to decline with age.  However, scientists have started to notice that Western women have too much estrogen rather than too little; girls are reaching puberty much earlier and the number of cases of breast cancer is growing at an alarming rate.

A large part of this has been attributed to the xenoestrogens (man-made estrogens) in our environment.  These synthetic estrogens can be found in our household cleaning products, cosmetics, plastic food wrapping to name but a few.

Eating too much sugar and processed food combined with a lack of good quality dietary fats and protein can also increase oestrogen levels.  And stress can make the imbalance worse as cortisol and progesterone fight for the same receptors on your cells.


The term androgen refers to a group of hormones best known for male sexual characteristics; hormones such as testosterone and DHEA-S (dehydroepiandrosterone sulfate).  But they’re not just for men.  They have a big impact on body weight and composition as one of their primary roles is to increase muscle and decrease fat.  They also have a powerful effect on the brain as they influence our mood and energy levels.

Where are testosterone and DHEA-S made?  In women they are produced in the adrenal glands and ovaries.

How do testosterone and DHEA-S affect metabolism?  Androgens have a powerful effect on body weight and composition.  They are steroid hormones which means they promote muscle growth but they also have a strong effect on the brain influencing your mood, energy levels and desire to exercise.

What causes androgen imbalance?  Testosterone and DHEA-S are both hormones of youth and our bodies produce less and less as we get older.  Men’s testosterone levels start to decline from as early as age 30 by about 1-2% per year.  This slow and steady decline (also known as “Andropause”) is in contrast to a woman’s more rapid loss of estrogen and progresterone during menopause.

The main cause of androgen problems in women is androgen excess with the most common cause being Polycycstic Ovarian Syndrome (PCOS).  Research into the causes and treatment of PCOS have improved hugely in recent years and we now know that insulin resistance is the underlying cause.  Androgen excess and excess weight go hand in hand and is also linked to other health problems such as high blood pressure, cholesterol problems, insulin resistance and diabetes.


The good news is that through nutrition, exercise and lifestyle you can start to redress your hormonal balance.


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