A lean body with muscles of steel evokes the association with testosterone for many. Now there is no denying that testosterone plays an important role in both muscle growth and fat loss. But do higher testosterone levels automatically mean more muscle and less fat?

WHAT IS TESTOSTERONE?

Testosterone is the main androgen (male sex hormone). Testosterone concentrations in blood are low before puberty and rise to adult values ​​during puberty.

Testosterone is produced in the adrenal glands and (in men) in the testes, about 7 mg/day in men. In women, testosterone concentrations are much lower. In this article we focus on the situation in men, in particular bodybuilders.

WHAT DOES TESTOSTERONE DO?

In adults, testosterone performs the following functions, among others:

• Muscles: increases muscle mass (protein synthesis) and muscle strength.
• Body Fat: Blocks fat absorption and storage and increases the number of fat-burning beta-adrenergic receptors.
• Brain: promotes cognition, memory and sex drive.
• Heart: increases blood flow and cardiac output.
• Bones: increases red blood cell production and bone growth and maintains bone density.
• Male Sexual Organs: supports sperm production and viability and promotes erectile function.
• Skin: supports collagen production and hair production.
• Kidneys: produces erythropoietin (EPO), which stimulates red blood cell production.

In addition, testosterone increases insulin-like growth factor (IGF-1) and healthy testosterone levels are associated with good health and immune function, a lower body fat percentage (see also below) and an increased metabolism.

WHAT ARE NORMAL TESTOSTERONE LEVELS?

Testosterone is therefore an important good. Fortunately, in most people enough testosterone is produced to be able to perform all the aforementioned tasks with verve.

The normal range of testosterone levels in adult males between the ages of 19 and 39 is 264-916 nanograms/deciliter ^[ xl ] . Testosterone levels above or below this range can cause symptoms. Research shows that the healthiest men have testosterone levels between 400 and 600 ng/dL ^[ i ] .

A normal male testosterone level peaks at about age 20, then it slowly declines. In men between the ages of 30 and 50, testosterone levels are likely to fall by about 1% per year ^[ ii ] . That shouldn’t be a problem, especially in men who naturally have relatively high testosterone levels. Others do experience problems, especially at a higher age (from 40-50 years). This drop in testosterone levels is sometimes referred to as hypogonadism, “male menopause,” or andropause.

By the way, the testosterone level in itself does not say everything. Possible complaints can also be related to the amount of “free testosterone” in the blood. Only the free, unbound form of testosterone is biologically active. In addition to the testosterone level, the ratio of bound and unbound testosterone in the blood is therefore also important. 9 to 30 ng/dL of free testosterone (2 to 3% of total testosterone) is considered normal in men.

As you can see the ranges are quite wide. What is a good testosterone level for one person may not be so for another ^[ iii ] . Therefore, pay attention to symptoms that indicate low testosterone levels, such as fatigue, sadness, loss of strength and reduced libido. Studies suggest that the likelihood of such symptoms is quite high at testosterone levels below 300 ng/dL in men aged 40 to 90 ^[ iv ] , and below 400 ng/dL in men under 40 years of age ^[ v ] .

Testosterone Replacement Therapy (TRT) is usually only used under medical supervision in men with a testosterone level below 300 ng/dL. About which a little more in a moment.

TESTOSTERONE AND MUSCLE GROWTH

Testosterone and muscle growth are inextricably linked, which is why bodybuilders are quick to prick up as soon as the ‘t’ word is spoken. More testosterone means more muscle mass, right? Unfortunately, the truth is more complicated. On the one hand, we must distinguish between acutely elevated testosterone levels (for example, as a result of training) and structural increases (the testosterone level at rest), and on the other, between natural and artificially elevated testosterone levels.

ACUTE ELEVATION

Strength training immediately increases the levels of testosterone, growth hormone and IGF-1, only to return to normal levels within an hour after training ^[ vi ] . We see strong acute increases especially when doing heavy compound exercises, such as squats and deadlifts.

However, research has shown that acute increases in testosterone levels have little or no correlation with increases in strength and lean muscle mass ^{[ vii ][ xli ][ xlii ]} . A greater hormonal response does not necessarily lead to more muscle growth.

The amount of muscle mass you build therefore mainly depends on the degree of overload during that training, and after the training through diet and rest. The temporary increase in testosterone level, during and immediately after training, is therefore in fact a by-product. A necessary by-product, by the way, because the testosterone increase probably compensates for the increase in another hormone value as a result of strength training, namely that of the (catabolic) ‘stress hormone’ cortisol.

Although most coaches agree that compound exercises are extremely effective for creating overload and thus stimulating muscle growth, but not specifically because of the high hormonal response they trigger: testorone and cortisol levels will rise similarly.

ANABOLIC STEROIDS

But what about resting testosterone levels? There is no doubt about a long-term unnatural increase in testosterone levels, usually through the administration of anabolic steroids: this usually leads to a significant increase in strength and muscle mass, even without strength training.

That increase will eventually cause you to have more muscle mass (and strength) than your natural potential would allow. For example, a review from the University of Maastricht shows that steroids users who do strength training can gain 2-5 kilograms of muscle mass in the short term (in less than 10 weeks) ^[ xii ] . The fastest measured muscle gain was nearly 6 kg in 10 weeks (0.6 kg per week) ^[ xiii ] . By way of comparison: in the most favorable circumstances (namely: as a starting strength athlete), a natural can gain a maximum of 1.2 kg of muscle mass per month (0.3 kg per week).

Anabolic steroids work by lifting testosterone levels above the natural ceiling for weeks, months or sometimes years. And they don’t quite do that: in the latter study, the men were given 600 mg of testosterone per week, causing their testosterone levels to shoot up by more than 600% on average. Nevertheless, we saw in that study that the difference in muscle growth potential between a starting natural (0.3 kg per week) and an average steroids user (0.6 kg per week) is not even that big.

TESTOSTERONE REPLACEMENT THERAPY (TRT)

The latter also explains why older men who follow TRT do not just turn into muscular bodybuilders: the dose they receive weekly is usually ‘only’ around 100 mg.

Nevertheless, they do benefit from this, also in terms of maintaining and growing muscle mass. This is not only because their natural values ​​are (too) low (which is the indication for TRT), but also because TRT ensures that testosterone levels are constantly elevated, while they normally fluctuate greatly throughout the day. In addition, with TRT you can often have a greater amount of free testosterone than is usually possible of course. TRT is therefore in fact ‘anabolic light’.

Learn more about TRT and why it isn’t as ‘natural’ as is often claimed in this video.

INCREASES WITHIN THE NATURAL MARGIN

We have seen that artificial increases in testosterone levels undeniably lead to (much) more muscle growth. But what about natural elevations? So if you manage to go from 400 to 600 ng/dL through lifestyle changes, for example? Do you also build muscle mass faster or easier, albeit to a lesser extent?

This question is not so easy to answer, despite the extensive scientific research that has been done. An overview of the most important studies can be found on Weightology.net, the website of muscle growth researcher James Krieger. He distinguishes between three types of research:

• Cross-sectional study: this measures the testosterone level and the amount of muscle mass of large groups of men, on the basis of which they are divided into different categories;
• Dose-response study: this involves manipulating testosterone levels, usually by a group of men first administering testosterone-suppressing drugs and then different doses of synthetic testosterone, in order to raise testosterone levels to different heights and compare their effects;
• TRT study: the testosterone level is artificially raised, whether or not in men with a (too) low testosterone level.

The results of the cross-sectional studies are clear: men with a higher testosterone level usually also have more muscle mass. However, that does not mean that they also build muscle mass faster: according to Krieger, that is probably not the case. He refers to women: although they have lower testosterone levels than men,  relatively speaking they can achieve muscle growth just as quickly as men ^[ xliii ] .

Cross-sectional studies say nothing about the effects of fluctuations in testosterone levels. That is why Krieger also looked at four dose-response studies, all of which show a relationship, albeit to different degrees, between testosterone level and muscle size: the higher the (engineered) testosterone level, the greater the lean body mass, even without strength training.

In TRT studies, that effect is, logically, much stronger. Men with a low testosterone level who are administered testosterone see a significant increase in their lean body mass, even without training and also with a relatively small increase in testosterone level (not even close to the upper limit of the natural range). However, we already saw that you cannot compare TRT with naturally increasing your testosterone level.

But also in the dose-response studies, the testosterone increases are still artificially manipulated and therefore cannot be compared with natural increases under the influence of, for example, lifestyle changes.

Krieger also acknowledges the latter, which is why he concludes that natural increases in testosterone levels within the natural range probably have at most a small effect on the speed at which you can build muscle. How much muscle mass you have and can build up is determined by the testosterone values ​​you naturally have and you can do little or nothing about that without steroids or TRT:

(…) Your testosterone levels affect how much muscle you carry around, whether you train or not. Then, when you begin to train, your responsiveness to training is mostly similar regardless of whether you have low or high testosterone levels. It may be a bit less with lower testosterone, but the biggest impact is on your baseline. ^[ xliv ]

That’s not to say it’s not worth boosting your testosterone level if you suspect it’s on the low side. According to coach Mike Israetel, increasing testosterone levels within the natural range can positively influence the process of muscle growth (a little): your muscles become more sensitive to muscle growth and your recovery capacity is increased somewhat ^[ xlv ] . In jargon: the margin in which you can apply overload, namely that between MEV and MRV, is increasing. Israel:

For any two individuals that are identical except for a genetic difference in circulating testosterone concentrations, there will be qualitative differences in the shapes of their respective adaptation curves. ^[ xlv ]

You may also benefit from naturally elevated testosterone levels in other ways: it may give you more energy, a higher libido and/or a better mood. The latter also translates into motivation to train.

Whether and the extent to which you benefit from a natural increase depends on how low your testosterone level actually is. For example, one study noted an increased libido with a testosterone increase from 230 to 500 ng/dL, but no increase in libido when going from 300 to 500 ^[ xiv ] .

TESTOSTERONE AND FAT LOSS

So far we have looked almost exclusively at testosterone and muscle mass. However, there is also a clear relationship between the testosterone level and the amount of body fat. That relationship even works both ways.

HOW TESTOSTERONE AFFECTS BODY FAT

Testosterone appears to suppress the creation of fat cells ^{[ xv ] [ xvi ] [ xvii ]} . Testosterone also stimulates the metabolism, so that the body uses more energy and therefore burns more fat ^[ xviii ] . So if you want to lose fat, for example as a bodybuilder in the cut, you seem to benefit from keeping your testosterone level up.

TRT has indeed been shown to be very effective in promoting fat loss in older men ^{[ xxiii ][ xxiv ][ xxv ][ xxvi ]} . In young men , however , this effect does not appear to be present , if at all ^[ xxvii ] . It is therefore questionable whether a natural increase in the testosterone level actually has much effect.

HOW BODY FAT AFFECTS TESTOSTERONE

But the relationship also works in reverse. Men with a high body fat percentage have lower testosterone levels ^[ xix ] . The culprit is mainly the belly fat. This contains aromatase, an enzyme that converts testosterone into the female sex hormone estrogen ^[ xx ] . As a result, you will put on even more fat, especially in the abdomen and chest area. A snowball effect.

Remarkably enough, a very low fat percentage also has negative consequences for the testosterone level. If you have such a fat percentage, for example 7%, the level of the hormone leptin is continuously low, so that your brain receives the signal that there is not enough energy available. Your body will then do everything it can to save energy (metabolic adaptation), including reducing testosterone production ^[ xxi ]. Also hunger, decreased resistance, decreased performance and general apathy are possible consequences of persistently low leptin levels. It is not for nothing that competition bodybuilders do not want to be ‘competition dry’ all year round. With a slightly higher fat percentage you function better in all respects, including in the gym.

For optimal testosterone levels and functioning in general, it is best for men to have a fat percentage of between 8 and 15% ^[ xxii ] .

INCREASE YOUR TESTOSTERONE LEVEL

Even though your testosterone level is probably okay, there are several things you can do to keep it up or increase it if you want. The main ones are:

• sleep well ^{[ xxviii ][ xix ][ xxx ][ xxxii ][ xxxiii ]} ;
• a high-carb -dietary pattern ^{[ xxxiv ] [ xxxv ] [ xxxvi ] [ xxxvii ]} ;
• do not eat mainly unsaturated, but also sufficient saturated fats ^{[ xxxviii ]} ;
• eat enough micronutrients, including zinc, magnesium and vitamin D*;
• don’t do too much endurance sport ^{[ xxxix ][ xxxi ]} ;
• lose fat (see previous section).

* supplementation is only necessary if regular diet does not provide this enough, which is usually not the case with a normal diet

These things fit into any healthy (bodybuilding) lifestyle, regardless of whether you want to increase your testosterone level.

TESTOSTERONE WHILE CUTTING

Even as a healthy (young) man with normal testosterone levels, you sometimes have to do something extra to maintain your testosterone level. In times of a lot of stress, for example, or if you follow a long-term calorie-restricted diet, as bodybuilders do when cutting.

Prolonged cutting usually leads to a drop in testosterone levels. This is under the influence of the metabolic adaptation we just talked about. Not a disaster in itself, since it is a temporary situation and your testosterone has quickly returned to normal levels after cutting.

Nevertheless, we would like to give you some tips to keep your testosterone level somewhat at a level during cutting:

• Don’t cut for too long: introduce regular refeeds and/or diet breaks to (partially) reverse metabolic adaptation;
• Do not eat more protein than is strictly necessary for muscle maintenance. Eating too much protein unnecessarily comes at the expense of the amount of carbohydrates and fats you can eat, while you desperately need both to maintain your testosterone level. 1.8 grams of protein per kilogram of body weight is usually sufficient (which is slightly higher than the regular recommendation of 1.6 g/kg/d and here’s why). Also, do not eat more fat than you strictly need: ~0.7 g/kg body weight is usually sufficient. For the rest you can eat carbohydrates. Carbohydrates contribute to the production of testosterone and are also the main source of energy for your training;
• Eat plenty of fruits and vegetables, and take supplements if you suspect you may not be getting all the micronutrients in sufficient amounts;
• Don’t do excessive cardio.

NATURAL TESTOSTERONE BOOSTERS (SUPPLEMENTS)

Natural testosterone boosters are supplements that contain one or more substances that are supposed to promote testosterone production. However, there is only a limited number of substances that have more or less been shown to have a (small) positive effect on testosterone levels as a supplement.

On the one hand, it concerns micronutrients that are already frequently in our regular diet, such as zinc and magnesium. Supplementing it only makes sense if you don’t get enough of these substances from yourself, which is rarely the case with an average diet, perhaps with the exception of vegan and highly calorie-restricted diets.

On the other hand, it concerns substances, mostly plant extracts, that are not or hardly in our food and are often handed down by the old (exotic) medicine. Some such substances that may ‘do something’ for your testosterone production are bulbine natalensis, boron, ashwagandha and D-aspartic acid. Sometimes several such substances are put in one product and thus touted as ‘testosterone boosters’.

The same applies to testosterone supplements : if a substance can already increase the testosterone level, supplementation is usually only useful in men with testosterone levels at the lower end of the natural spectrum. But don’t expect that you will build muscle more easily.

There are also so-called libido boosters, which do not influence the testosterone level, but do stimulate the sex drive, such as maca and tribulus terrestris. These are often incorrectly marketed as a bodybuilding supplement.

WHEN IN DOUBT

In your twenties and thirties you normally don’t have to worry about your testosterone level. If you think you are experiencing symptoms of a low testosterone level or even a deficiency, have your testosterone level checked by your doctor.

IN SUMMARY

Testosterone and muscle mass are inextricably linked. Usually, the higher the basal testosterone level a person has naturally, the greater the amount of muscle mass (seen without strength training). However, a higher testosterone level does not mean that you also build muscle mass faster than someone with lower values, at least not as long as the testosterone levels are within the natural range (264-916 nanograms/decilitre).

Fluctuations within that natural range are usually not or hardly noticeable. If you manage to increase your testosterone level naturally, for example through lifestyle changes, this might have a small effect on the speed at which you build muscle mass, especially when a testosterone level is increased that is at the lower end of the natural range. You may also notice other positive effects of that increase, such as more energy and a higher libido.

If your testosterone level is structurally low or too low, there may be a medical indication for this, whether or not in combination with old age. In that case, you should see your doctor and you may need treatment such as Testosterone Replacement Therapy (TRT).

Artificial increases in testosterone levels, such as through anabolic steroids and to a lesser extent TRT, do allow you to build muscle much faster than normal. And with long-term use, you can build more muscle mass than your genetic potential would allow.

In your twenties, thirties and even forties you normally don’t have to worry about your testosterone level with a normal, healthy lifestyle. Only if you often sleep badly, are under a lot of stress, eat an unhealthy diet, are very overweight and/or consume a lot of alcohol, can your testosterone level significantly lower. Then it is a matter of improving your lifestyle on the aforementioned points.

Finally, bodybuilders who cut for a long time sometimes have to contend with low testosterone levels. In that case, the advice is to continue to eat as many carbohydrates as possible despite the calorie restriction (with due observance of the recommended minimum amounts of proteins and fats), to keep the intake of micronutrients at the right level (if in doubt, use a supplement) and not to go too long in one go. to cut. Also, don’t do too much cardio.

Possibly also so-called testosterone boosters can help a little to increase your testosterone level when it is on the low side, for example as a result of prolonged cutting. Study the composition critically before purchasing such a supplement. With normal testosterone levels, a supplement will not produce noticeable effects.

REFERENCES

• ^[i] https://www.medicinenet.com/high_and_low_testosterone_levels_in_men/views.htm
• ^[ii] https://www.livestrong.com/article/228100-when-does-your-testosterone-level-start-to-drop/
• ^[iii] https://examine.com/nutrition/increase-testosterone-naturally/
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