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Men’s Quest For Peak Physical Attractiveness Is Creating A Fertility Paradox


Katy Evans

Katy is Managing Editor at IFLScience where she oversees editorial content from News articles to Features, and even occasionally writes some.

Managing Editor


Long-term steroid use can lead to permanent infertility. Italo/Shutterstock

Scientists have described a new paradox surrounding men’s quest to make themselves more attractive to the opposite sex that is potentially harming their fertility.

The Mossman-Pacey paradox, named after the researchers who first described it, posits the contradiction that men trying to achieve a perceived notion of fitness or attractiveness that will make them more sexually appealing are instead damaging their “evolutionary fitness”, reducing their chances of passing on their genes.


In the Journal of Internal Medicine, Dr James Mossman and Professor Allan Pacey describe the fitness paradox – specifically the abuse of anabolic-androgenic steroids (AAS) by men to gain muscles – as an evolutionary contradiction.  

"Some men use and abuse drugs to enhance bodily features – presumably to increase their attractiveness – and these drugs are paradoxically making them infertile in the process," Dr Mossman told IFLScience. "Thus, their perceived ‘fitness’, and their evolutionary ‘fitness’, are in direct conflict since evolutionary fitness is measured as the number of offspring.

"In evolutionary terms, no sperm = no babies = zero fitness."

Steroids are most recognizably used by bodybuilders to speed up the body's natural muscle-building process. Dr Mossman first noticed the connection between likely steroid use and fertility issues while investigating male fertility and sperm quality during his graduate studies at the University of Sheffield.


"During the recruitment of over 500 men, I noticed that a small proportion of them were massively muscular with physiques most likely obtained via steroid use. On assessing their semen samples, it was clear this was a group of men who were at the very lowest end of the range of sperm production. Most of them had zero sperm in their samples!" Dr Mossman said.

"In discussion with Allan Pacey, he described how steroid use/abuse was well recognized in the infertility field, but men poorly understood that attempting to conceive while taking steroids was often futile. This jumped out as a clearly paradoxical situation."

Anabolic steroids are performance-enhancing drugs used to increase muscle mass that synthetically produce the hormone testosterone. However, they can block the actual production of testosterone by fooling the brain’s pituitary gland – which controls most hormone glands in the body – into thinking the testes, which produce the sex hormone, are overproducing. The glands react by stopping the production of two key hormones that produce sperm.

However, it’s not just steroids creating the paradox. Researchers in Denmark used the Mossman-Pacey paradox, again in the Journal of Internal Medicine, to highlight the Catch-22 of using finasteride to treat male pattern hair loss. Balding men are more likely to use hair loss treatments to make them feel more attractive, but finasteride can cause both sexual dysfunction and infertility.


Asked why men are being driven to extremes in the pursuit of peak "fitness", Dr Mossman told IFLScience: "I think the exposure of ‘ideal’ body images that both women and men suffer at the hands of advertisers, the media, and Hollywood all but ensures body image disorders and lowered self-esteem in the population... At a very early age, children are exposed to a ‘desired’ body shape and these imprinted images must have a down-stream influence on perceived attractiveness." 

The paradox is that men who on first appearance look like they are genetically superior and thus have a good chance of passing on their genes, in reality, have a very low probability of being able to reproduce successfully.

The good news is that the damage can be reversed once the steroid use stops, but it can take up to a year for sperm production to be normal again. However, long-term use can risk permanent infertility. Dr Mossman also points out that fertility rates are highly variable in a population anyway, and any men concerned about their fertility "should seek professional medical advice (not from their gym buddies) and be honest to their clinicians about their history of steroid use."  

Professor Pacey and Dr Mossman call steroid use a "growing public health concern" and hope that as the dangers of using them are already well known, yet attitudes have proven a challenge to change, perhaps pointing out the futility of trying to procreate while on them might get through to the men at risk.


"The paradox we describe hopefully highlights that trying to conceive while abusing steroids is an absurd idea," Dr Mossman said.


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