Testosterone, leptin, body fat levels and how they correlate

Testosterone, leptin, body fat levels and how they correlate

We all know that testosterone is the king of muscle building hormones, not to mention the hormone which drives men to compete, go to war, and pursue the faintest whiff of female attention with the enthusiasm of a rabid dog in heat. Yes, testosterone is all these things but the one thing you probably don’t really think in relation to testosterone is its impact on body fat. As such a recent study (1) on the interplay between androgens (the class of hormones which testosterone belongs to) and adipose tissue is something which was long overdue.



The researchers start by giving a primer on the role of adipose tissue as a storage point for triglycerides and how, unlike the old view of fat as an inactive reserve of energy, it actually has multiple roles in regulating energy balance, appetite, hormone levels and much more. They point out that it is comprised of white and brown adipose tissue and sub-divided into visceral fat (fat around the organs beneath muscles) and subcutaneous fat (that roll of fat over your belly). They correctly state that visceral fat is more responsive to cortisol and can cause more health complications.



Leptin, in case you have been buried under a rock for the last 15 years functions as a master hormone which has a controlling function on the level of the hormones you know well, such as testosterone for one. Leptin came to prominence in 1994 in research which showed how a particular mouse which produced no leptin at all, magically lost body fat when injected with leptin. This led to an arms race as pharmaceutical companies sought to release leptin based weight loss drugs only to find in trials that they made very little difference to weight loss. This was when we found out that, unlike mice, obese humans tended to have high circulating leptin levels which indicated that the problem might not be a lack of leptin but that they had become resistant to its effects.

The researchers here state that excessive leptin is not only associated with increased adipose tissue but it has a negative impact on testosterone production via the negative effect of leptin on Leydig cell function (2). Importantly, this occurs at concentrations within the range of leptin levels seen in obese men. No surprise then to note that obese men have reduced testosterone levels (3). I should point out that this does not mean leptin makes you fat but rather that fat people become resistant to its effects. We will discuss later how falling leptin levels are actually a big problem for dieters looking to maximise fat loss without losing muscle mass. Our article on dieting without losing muscle mass explains how we can avoid the pitfalls of dieting by adopting specific steps to maximise fat loss and conserve muscle mass.


Testosterone, Dihydrotestosterone and Estrogen

Testosterone in the body is classed as either free, bound to albumin or bound to sex hormone binding globulin (SHGB). Of importance to us it that free testosterone which comprises a tiny portion of the total amount of testosterone (2%) and albumin bound (approx 50%) is bioavailable to the body and correlated to muscle mass and strength, as well as showing a negative correlation for fat mass.

As well as testosterone, two other significant hormones are DHT and estrogen, and testosterone can be converted to both but they have very different effects. DHT is more potent than testosterone and can lead to increased fat loss and muscle hardening while estrogen, as you might guess, can lead to fat gain (4). Of note, testosterone can convert to estrogen via the actions of the aromatase enzyme which is found in fat. What this means is the more fat you have, the greater the potential for testosterone converting into estrogen via the actions of aromatase. Interestingly, the use of an aromatase inhibitor is associated with a decline in leptin levels (5) as well as a rise in testosterone which all aromatase inhibitors will produce. This means avoiding getting too fat when bulking is essential as the fatter you get, the faster you will get fat!

Low Testosterone levels predict metabolic syndrome

Metabolic syndrome is a name given for a condition marked by excessive visceral fat, low muscle mass, hypertension, diabetes and insulin resistance. Numerous studies have shown an association between obesity, low testosterone, and metabolic syndrome (6-9) with low testosterone causing fat gain, which in turn can lead to increased susceptibility for other symptoms of metabolic syndrome. This sets up a cycle where, as testosterone drops, obesity and health markers deteriorate causing a further reduction in testosterone which then leads to more weight gain and increased predisposition to diabetes and other serious medical conditions.

On the other hand, weight loss in obese men with metabolic syndrome showed a rise in free testosterone (10) and treatment of obese men with insulin resistance (meaning their muscle cells are less responsive to insulin, leading to inability to uptake amino acids and glycogen into muscle) shows they lose fat and increase lean body mass while simultaneously improving across a range of health markers.



The authors conclude by saying:

“In conclusion, adequate levels and balance of circulating sex hormones are necessary to maintain a correct distribution and size of adipose tissue, which in turn is fundamental to keep a normal reproductive and sexual function. The delicate issue of whether testosterone decline, observed with aging, causes adipose tissue accumulation, or whether weight gain primarily disrupts testicular steroidogenesis, is still unclear and needs further studies.”


Our Comments

The first thing to say here is that the view that testosterone is linked to fat gain can be comprehensively rejected. While this may seem obvious in light of the above, it bears repeating as some people have suggested the prevalence of steroid using bodybuilders with protruding guts is a result of them gaining significant amounts of visceral fat through the influence of androgens. The review of the research here shows that it is low testosterone levels that are most likely to be associated with fat gain, as well as a range of side effects associated with fat gain such as increased susceptibility for gynecomastia, insulin resistance, hypertension and diabetes.


Practical Recommendations

While we can of course use testosterone boosters to increase testosterone, following a lifestyle that encourages us to naturally increase testosterone levels ensures we optimise both muscle and strength while staying lean. Read our article on naturally increasing testosterone.

Use a testosterone booster such as Testforce 2, Triazole or Erase Pro. Testosterone boosters can lead to your body more than doubling testosterone output which will lead to a powerful muscle gaining/anti-fat effect.


Do not fear leptin because of its association with obese people. Rather, consider it as less a hormone that prevents obesity which it clearly fails at, and more as something that acts to prevent starvation. Dieting reduces leptin levels which cause a catabolic environment leading to muscle loss. Periodic high carb, low fat refeeds can spike leptin in the short term in dieters. Here is the key point – spiking leptin in individuals who are lean and exhibiting low leptin levels absolutely will bump up metabolic rate and enhance hormonal profile leading to increased fat loss and reduced muscle mass. In fact, it is fair to say the leaner you get, the MORE useful you will find a refeed strategy to bump up leptin.

In lean individuals as well those who exercise and take supplements such as fish oil, it is shown (11) that they exhibit greater leptin sensitivity which makes them more responsive to leptin’s effects. If you are dieting and interested in keeping testosterone levels up then regular refeeds, a testosterone booster, a testosterone boosting lifestyle, and possibly the use of a supplement such as L-Dopa which can boost dopamine levels (which in turn can help to trick the brain into raising leptin levels) can all help ensure increased success from your diet.


Wrapping Up

We have seen that there is a correlation between low testosterone and increased fat and poor health, as well as an association with high leptin levels. As athletes we need to protect against fat gain at all times to prevent the reduction in testosterone and increased conversion to estrogen associated with fat gain. By employing a careful approach to lifestyle, diet and supplements we can ensure that we remain lean, and our testosterone levels remain as high as possible while dieting.


Author: Reggie Johal



1. Caterina Mammi et.al (2012): Androgens and Adipose Tissue in Males: A Complex and Reciprocal Interplay

2. Caprio M, Isidori AM, Carta AR, Moretti C, Dufau ML, Fabbri A. (1999): Expression of functional leptin receptors in rodent Leydig cells.

3. Zumoff B, Strain GW, Miller LK, et al. (1990): Plasma free and non-sex-hormone-binding-globulin-bound testosterone are decreased in obese men in proportion to their degree of obesity.

4. Bélanger C, Luu-The V, Dupont P, Tchernof A (2002): Adipose tissue intracrinology: potential importance of local androgen/estrogen metabolism in the regulation of adiposity.

5. Lapauw B, T’Sjoen G, Mahmoud A, Kaufman JM, Ruige JB (2009): Short-term aromatase inhibition: effects on glucose metabolism and serum leptin levels in young and elderly men.

6. Blouin K, Després JP, Couillard C, et al. (2005): Contribution of age and declining androgen levels to features of the metabolic syndrome in men.

7. Muller M, Grobbee DE, den Tonkelaar I, Lamberts SWJ, van der Schouw YT (2005): Endogenous sex hormones and metabolic syndrome in aging men.

8. Laaksonen DE, Niskanen L, Punnonen K, et al. (2005): The metabolic syndrome and smoking in relation to hypogonadism in middle-aged men: a prospective cohort study.

9. Derby CA, Zilber S, Brambilla D, Morales KH, McKinlay JB (2006); Body mass index, waist circumference and waist to hip ratio and change in sex steroid hormones: the Massachusetts male ageing study.

10.  Niskanen L, Laaksonen DE, Punnonen K, Mustajoki P, Kaukua J, Rissanen A (2004): Changes in sex hormone-binding globulin and testosterone during weight loss and weight maintenance in abdominally obese men with the metabolic syndrome.

11. Dyck DJ (2006): Leptin sensitivity in skeletal muscle is modulated by diet and exercise.

© 2012, Reggie Johal. All rights reserved.