How Obesity Impacts Testosterone

Take-home points

• Obesity affects overall health and significantly disrupts hormonal balance, particularly testosterone levels.
• Low testosterone results in various health issues including sexual dysfunction, muscle loss, fatigue, depression, cognitive decline, and increased risk of cardiovascular diseases and diabetes.
• Obesity reduces testosterone through various mechanisms, disrupting cells responsible for testosterone production.
• Weight loss can help improve testosterone levels in obese subjects, though lifestyle changes such as diet, exercise, stress management, and sleep, with medications and surgery as options for severe cases.

Obesity, a widespread health challenge affecting millions globally, is more than just a number on the scale — it has profound implications for overall health and well-being. Almost no part of the body is left unscathed by obesity, though whilst it is common knowledge that excess body fat impairs blood sugar, cardiovascular function and the heart, knowledge of the harmful effects on hormonal balance, particularly testosterone levels, is less widespread.

Learn more about the causes of obesity

What is testosterone?

Testosterone, a vital hormone primarily associated with male health but also important for women, plays a crucial role in regulating energy levels, muscle mass, mood, and sexual function, amongst others. Given these important functions of this hormone, it is concerning that testosterone levels in men around the world are in decline¹. Whilst some of the factors contributing to this remain up for debate, one is known for sure: obesity. Obesity has been described to be the single most important factor associated with low testosterone, even more so than age.^2,3

In order to shed more light on this important topic, this article will first describe the health effects of reduced testosterone and how obesity-associated low testosterone is diagnosed. The mechanisms underlying this relationship are then described, before concluding with the available options for those affected.

The health effects of low testosterone

The involvement of testosterone in various systems across the body means the consequences can be far-reaching. Given its primary role as a sex hormone, it is not surprising that low testosterone can affect sexual function, manifesting in reduced libido, erectile dysfunction, and decreased sexual satisfaction during sex. Another famous role of testosterone is its muscle-promoting effects, which can be seen in bodybuilders using synthetic derivates of testosterone to grow huge amounts of muscle. Low testosterone is associated with low skeletal muscle mass and strength, which is undesirable given that skeletal muscle promotes metabolic health and strength and is associated with lower mortality.⁴

However, testosterone also has other functions beyond its sexual- and muscle-orientated ones. Testosterone promotes bone health⁵ and is also involved in regulating mood and cognitive function, reflected in the fact that low testosterone is associated with depression and cognitive decline.^6,7 Low testosterone can also impair energy and lead to feelings of fatigue, which, aside from being unpleasant, can further impact well-being by reducing willingness to exercise and remain active. Additionally, appropriate levels of testosterone regulate inflammation. Consequently, low testosterone can promote an inflammatory state in the body, increasing the risk of cardiovascular disease, type 2 diabetes and metabolic syndrome.⁸

A complete breakdown of low testosterone can be found here

How does obesity cause low testosterone?

The mechanisms by which obesity leads to a reduction in testosterone can be complicated, involve multiple systems across the body, and are still being elucidated. With mild levels of obesity (~30–35kg/m²), testosterone is thought to be lower mostly due to a reduction in a protein called sex hormone-binding globulin (SHBG). SHBG binds to testosterone and transports it to tissues. When SHBG is lower, the level of free testosterone (i.e., testosterone not bound to SHBG) increases. In obesity, this free testosterone is now exposed and can be converted to oestrogen by enzymes released by fat tissue². Since there is more fat tissue in obese individuals, more of this enzyme is released.

As obesity becomes more extreme (>35kg/m2), testosterone production also becomes affected. Metabolic hormones like insulin and leptin are consistently elevated in obesity, which can eventually lead to insensitivity to their effects (this is also known as resistance, such as in “insulin resistance”). Aside from their metabolic functions, these hormones can also impact testosterone production. For example, elevated insulin and insulin resistance can impair the function of the cells in the testes that produce testosterone, whereas leptin resistance leads to a reduction in the release of hormones from the brain (more specifically, the pituitary gland) which stimulate testosterone production and directly inhibits testosterone secretion in the testes.

In addition to these effects, obesity also promotes inflammation in the body. The effects of inflammation are far-reaching but one of those more relevant to our discussion is the impairment of testosterone production by cells in the testes.⁹ Another common consequence of obesity is obstructive sleep apnoea, which refers to short periods of interrupted breathing during sleep. This is more common in obese individuals as the accumulation of fat tissue causes a narrowing of the upper airways.¹⁰ This reduces sleep quality, which in turn negatively impacts testosterone production.¹¹

The vicious cycle of obesity and testosterone

Recalling that some of the effects of testosterone include reducing fat mass and increasing muscle mass, it follows that obesity-induced testosterone reduction can also exacerbate obesity. This creates a negative feedback loop whereby as fat mass increases, testosterone decreases, which leads to a further increase in fat mass and a decrease in muscle mass. This can increase the challenge for those suffering from obesity but also highlights the importance of taking action before letting things get out of hand.

Treatment of obesity-induced low testosterone

Diet

Because the effects of obesity on testosterone are reversible, reducing body fat usually leads to an improvement in testosterone levels. The first line of action is lifestyle changes to manage body fat. Dietary approaches to reduce caloric intake and improve diet quality include increasing fruit and vegetable consumption and fibre and protein intake, as well as decreasing consumption of calorie-dense and processed foods.

Exercise

Regular exercise is also important, including both cardiovascular training (such as running, swimming, cycling, etc.) and, possibly even more important, resistance exercise, i.e., weight training. It’s also important to remain active throughout the day, especially if you have a stationary job. This could include taking the stairs instead of the lift, walking to work, using a standing desk or simply being mindful to interrupt long periods of sitting with short periods of movement.

Stress and sleep

Stress and sleep are also massive players in obesity. When both of these factors are not in order, appetite is elevated and satiety is decreased, both of which increase the chances of overeating. Both also reduce participation in exercise and performance during exercise, which further increases the risk of having a positive energy balance and fat accumulation. Finally, the body is more likely to store fat versus use it for energy when stressed or in a state of sleep deficiency.

Medications

Pharmacological interventions can also be useful, including GLP-1 inhibitors (the anti-obesity medications) such as semaglutide, although these should only be taken under the prescription of a medical professional. Finally, in extreme cases of obesity, surgical intervention via bariatric surgery can be considered.

Since testosterone has positive effects on fat and muscle mass, the use of testosterone in combination with lifestyle interventions in men with obesity-associated low testosterone has been studied. Whilst this remains an interesting option, more research is needed to confirm its efficacy over lifestyle interventions alone. In most cases, if fat mass can be reduced without the need for pharmaceutical or surgical interventions, testosterone should return to normal. However, testosterone replacement therapy in men with a confirmed diagnosis of hypogonadism (low testosterone with symptoms) is recommended in cases where lifestyle interventions have failed to address the cause, such as obesity.  

A complete breakdown testosterone replacement therapy can be found here

Concerned about your low testosterone levels?

If you are experiencing symptoms of low testosterone, or any symptoms, it is important to visit your healthcare professional for a professional diagnosis.  

References

1. Travison, T. G., Araujo, A. B., O’Donnell, A. B., Kupelian, V., & McKinlay, J. B. (2007). A Population-Level decline in serum testosterone levels in American men. the Journal of Clinical Endocrinology and Metabolism/Journal of Clinical Endocrinology & Metabolism, 92(1), 196–202. https://doi.org/10.1210/jc.2006-1375
2. Fernandez, C. J., Chacko, E. C., & Pappachan, J. M. (2019). Male obesity-related secondary hypogonadism – Pathophysiology, clinical implications and management. European Endocrinology, 15(2), 83. https://doi.org/10.17925/ee.2019.15.2.83
3. Grossmann, M. (2018). Hypogonadism and male obesity: Focus on unresolved questions. Clinical Endocrinology, 89(1), 11–21. https://doi.org/10.1111/cen.13723
4. Wang, Y., Luo, D., Liu, J., Song, Y., Jiang, B., & Jiang, H. (2023). Low skeletal muscle mass index and all-cause mortality risk in adults: A systematic review and meta-analysis of prospective cohort studies. PloS One, 18(6), e0286745. https://doi.org/10.1371/journal.pone.0286745
5. Shigehara, K., Izumi, K., Kadono, Y., & Mizokami, A. (2021). Testosterone and Bone Health in Men: A Narrative review. Journal of Clinical Medicine, 10(3), 530. https://doi.org/10.3390/jcm10030530
6. Khera, M. (2013). Patients with testosterone deficit syndrome and depression. PubMed, 66(7), 729–736. https://pubmed.ncbi.nlm.nih.gov/24047633
7. Beauchet, O. (2006). Testosterone and cognitive function: current clinical evidence of a relationship. European Journal of Endocrinology, 155(6), 773–781. https://doi.org/10.1530/eje.1.02306
8. Zitzmann, M. (2009). Testosterone deficiency, insulin resistance and the metabolic syndrome. Nature Reviews. Endocrinology, 5(12), 673–681. https://doi.org/10.1038/nrendo.2009.212
9. Tremellen, K., McPhee, N., Pearce, K., Benson, S., Schedlowski, M., & Engler, H. (2018). Endotoxin-initiated inflammation reduces testosterone production in men of reproductive age. Endocrinology and Metabolism/American Journal of Physiology: Endocrinology and Metabolism, 314(3), E206–E213. https://doi.org/10.1152/ajpendo.00279.2017
10. McFarlane, S. I. (2017). Obstructive sleep apnea and obesity: implications for public health. Sleep Medicine and Disorders: International Journal, 1(4). https://doi.org/10.15406/smdij.2017.01.00019
11. Liu, P. Y., & Reddy, R. T. (2022). Sleep, testosterone and cortisol balance, and ageing men. Reviews in Endocrine and Metabolic Disorders, 23(6), 1323–1339. https://doi.org/10.1007/s11154-022-09755-4