Obesity, left unchecked, has the potential to outpace smoking as the leading preventable cause of death in the United States.¹ Obesity raises LDL (“bad”) cholesterol and triglycerides, lowers HDL (“good”) cholesterol, and interferes with how the body responds to insulin. Over time, this imbalance drives up blood sugar and inflammation, setting the stage for heart disease, stroke, diabetes, and other chronic illnesses.
But beyond the cardiovascular and metabolic impacts, excess weight can undermine one of men’s most defining hormones: testosterone. Obesity and low testosterone form a self-perpetuating loop that affects everything from energy and metabolism to fertility and confidence. The heavier a man becomes, the lower his testosterone tends to fall – and as testosterone drops, body fat accumulates even faster.
The better we understand this cycle, the more strategically we can intervene to restore hormone balance and improve men’s health.
Understanding Testosterone
Most of us think of testosterone as the ‘male hormone’ because it’s responsible for many of the traits that define male physiology: muscle mass, bone strength, body hair, and the deep voice that emerges at puberty. But it’s also a primary player in reproductive function, sperm production, libido, mood regulation, and even energy levels and metabolism. Simply put, it affects nearly every aspect of men’s physical and mental well-being.
Testosterone levels naturally rise during puberty, peak in early adulthood, and then remain relatively stable for years before gradually declining after 45. Most men retain adequate levels well into older age, but certain factors can accelerate this decline. Among the most significant is obesity. While aging contributes to a slow, predictable drop in testosterone, excess body fat, especially in the midsection, can push levels far lower, and much faster, than time alone. Studies show that waist circumference is an even stronger predictor of low testosterone than body mass index (BMI) – a four-inch increase in waist size can raise a man’s odds of having low testosterone by 75%.¹
One of the mechanisms by which obesity disrupts hormone balance is through aromatase activity. Fat tissue contains an enzyme called aromatase, which converts testosterone into estrogen. The more adipose tissue a man has, the more testosterone gets converted, tipping the hormonal scales and reducing the levels of this vital male hormone.²
Obesity also lowers levels of sex hormone-binding globulin (SHBG), the protein that carries testosterone through the bloodstream. With less SHBG, the amount of free, biologically active testosterone drops, even if total testosterone levels appear only modestly reduced.²
Obesity is also closely linked with hyperleptinemia, a state of elevated leptin levels. Leptin normally helps regulate appetite and energy balance, but chronic excess can cause leptin resistance. This resistance can suppress the hypothalamic-pituitary-gonadal (HPG) axis (the brain-to-testes signaling pathway that controls testosterone production) by inhibiting gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion. In other words, the brain’s commands to produce testosterone are dulled.²
Insulin resistance and chronic low-grade inflammation, both common in obesity, further impair the HPG axis and directly affect Leydig cells in the testes, which are responsible for testosterone production. The result is a functional, yet potentially reversible, hypogonadism called pseudo-hypogonadism: the testes are still capable of producing testosterone, but systemic factors prevent them from doing so effectively. Removing those factors helps with regaining functionality. Sustained weight loss, whether through diet, exercise, or medical interventions, can restore testosterone levels and help break this self-perpetuating cycle.²
Understanding Bidirectionality
Low levels of testosterone also turn the tables on adipose storage, creating a vicious cycle. Just as excess fat can lower testosterone, low testosterone levels can accelerate fat accumulation, particularly in the abdominal region, while reducing lean muscle mass. This combination worsens metabolic dysfunction, insulin resistance, and glucose intolerance, making weight management even more challenging.
Research also shows that low testosterone can impair mitochondrial function in muscle, reduce insulin sensitivity, and increase visceral fat storage, exacerbating the feedback loop that accelerates metabolic decline. Men with both obesity and low testosterone often show worsened glucose tolerance, higher waist-to-hip ratios, and more pronounced dyslipidemia than those with obesity alone.³
An offshoot of this interplay between obesity and testosterone is erectile dysfunction (ED), which is in itself affected by either on its own and compounded by their simultaneous presence; ED can be one of the first visible signs that something is off hormonally or metabolically.
Low testosterone is rarely the sole cause of erectile dysfunction (ED), but testosterone still has a huge impact on sexual desire, libido, and overall sexual function. While normal adult testosterone levels are not strictly required for erections, hypogonadism (the most common endocrine disorder linked to ED) can reduce sexual interest and responsiveness. ⁴
Obesity itself increases the risk of ED through several mechanisms. Excess abdominal fat contributes to vascular dysfunction, insulin resistance, and inflammation, all of which impair blood flow to the penis. Studies show that men with larger waist circumferences or higher BMI have significantly higher odds of developing ED, independent of age. ⁵
When low testosterone and obesity coexist, their effects on erectile function multiply. Reduced testosterone can dampen libido and sexual confidence, while obesity impairs the physiological ability to achieve and maintain an erection. Even moderate weight loss has been shown to reverse ED in many men, highlighting the interconnectedness of metabolic health, testosterone, and sexual function. ⁶
The bidirectionality of testosterone and increased body mass explains why traditional weight loss efforts alone may only partially restore testosterone levels, and why interventions that address both hormones and metabolism together (such as lifestyle modification combined with medical therapies) can be more effective in the long run. ⁶ Targeted strategies based on individualized health characteristics are the most effective way to truly break the cycle and restore men’s health.
Breaking the Cycle
Lifestyle modification is at the root of almost any ailment, whether or not medical intervention is involved. Restoration of hormone balance is no exception, as diet, exercise, and sustained weight loss can improve testosterone levels, reduce visceral fat, and even reverse erectile dysfunction in many men.
For men with confirmed hypogonadism, testosterone therapy (TTh) can amplify the benefits of lifestyle interventions:
- Fat Reduction and Muscle Preservation: TTh reduces visceral fat and total body fat while preserving lean muscle mass, something diet and exercise alone often struggle to achieve. ⁷
- Metabolic and Hormonal Effects: By increasing bioavailable testosterone, TTh can help mitigate some of the systemic suppression of the HPG axis commonly observed in obesity.
- Motivation and Energy Rebound: TTh can improve energy, mood, and motivation, making it easier for men to adhere to diet and exercise programs. ⁸
Research consistently shows that pairing TTh with lifestyle modification produces the best results. For example, a 56-week randomized controlled trial in men with obesity and low testosterone found that those receiving TTh plus a very-low-calorie diet lost significantly more visceral fat, preserved lean muscle, and maintained weight loss better than those only refining their diets. ⁸ Targeting both simultaneously interrupts the self-perpetuating cycle more effectively than addressing either condition alone.
Regaining Control
With targeted interventions, men can restore hormone balance, reduce body fat, preserve muscle, and improve both metabolic and sexual health. To know if your weight puts you at risk for testosterone deficiency or related health issues, calculating your BMI, measuring waist circumference, getting precise assessments, and discussing testosterone levels with a healthcare provider are practical first steps.
For men with obesity and low testosterone, combining lifestyle changes with medical therapies like testosterone replacement offers the greatest potential to interrupt the effects that they have on each other. Even modest weight loss, when paired with targeted hormonal support, can help restore vitality, enhance sexual function, and lay the groundwork for long-term health.
Dr. Kapadia helps men address hormone imbalances, metabolic roadblocks, and lifestyle factors to help them regain control over their health, energy, and confidence. Schedule a consultation so you can start seeing everyday improvements in your sexual wellness, vitality, and stamina.
Note: TTh is not recommended for men without symptomatic hypogonadism, and potential risks, including fertility issues and sleep apnea, must be considered. Speak with a qualified health practitioner before beginning hormone therapy or engaging in new lifestyle modifications, especially if you have underlying health conditions.
Resources:
- Harvard Health Publishing. (2011, March 1). Obesity: Unhealthy and unmanly. Harvard Health; Harvard Health Publishing | Harvard Medical School. https://www.health.harvard.edu/mens-health/obesity-unhealthy-and-unmanly.
- Varnum, A. A., Pozzi, E., Deebel, N. A., Evans, A., Eid, N., Sadeghi-Nejad, H., & Ramasamy, R. (2023). Impact of GLP-1 Agonists on Male Reproductive Health—A Narrative Review. Medicina, 60(1). https://doi.org/10.3390/medicina60010050.
- Caliber, M., & Saad, F. (2020). Testosterone Therapy for Prevention and Treatment of Obesity in Men. Androgens: Clinical Research and Therapeutics, 1(1). https://doi.org/10.1089/andro.2020.0010.
- Rajfer J. (2000). Relationship between testosterone and erectile dysfunction. Reviews in urology, 2(2), 122–128. PMID: 16985751.
- Harvard Health Publishing. (2011, March 1). Obesity: Unhealthy and unmanly. Harvard Health; Harvard Health Publishing | Harvard Medical School. https://www.health.harvard.edu/mens-health/obesity-unhealthy-and-unmanly.
- Caliber, M., & Saad, F. (2020). Testosterone Therapy for Prevention and Treatment of Obesity in Men. Androgens: Clinical Research and Therapeutics, 1(1). https://doi.org/10.1089/andro.2020.0010.
- Kelly, D. M., & Jones, T. H. (2015). Testosterone and obesity. Obesity reviews : an official journal of the International Association for the Study of Obesity, 16(7), 581–606. https://doi.org/10.1111/obr.12282.
- Caliber, M., & Saad, F. (2020). Testosterone Therapy for Prevention and Treatment of Obesity in Men. Androgens: Clinical Research and Therapeutics, 1(1). https://doi.org/10.1089/andro.2020.0010.