- Increased visceral fat can raise an enzyme called aromatase that turns T into estrogen. It can also raise inflammation and lower a protein involved in controlling the amount of estrogen and testosterone actively present in the body.
- GLP-1s help to reverse low T count caused by fat gain. Doctors say tirzepatide (Mounjaro) may work better at boosting testosterone than semaglutide (Ozempic).
- Doctors warn that GLP-1s can cause muscle loss in addition to fat loss. Despite the potential testosterone boost, guys might initially feel more tired even if a guy’s bloodwork is headed in the right direction.
AMID THE TALK on GLP-1 benefits, there’s also been considerable chatter on its side effects. Ozempic butt, Ozempic face…you get the picture. If GLP-1s are affecting different parts of the body, you might wonder what else it might be affecting. Well, you’re not the only one. For the past few years, scientists and doctors have been keeping a close eye on GLP-1’s interaction with other hormones. Namely, testosterone.
This isn’t a far-off concern. Testosterone and body weight are closely connected. Yes, low T can lead to weight gain. But most of the time, the lower testosterone production is because of obesity.
“Most guys have this backwards,” says Justin Houman, MD, assistant professor of urology at Cedars-Sinai Medical Center. “They think low testosterone is what made them gain weight, but it’s usually the other way around, and it snowballs.”
With 1 in 8 Americans on a GLP-1, how do these medications affect this relationship? After years of research and close observation with patients, we have answers on what’s going on.
The Science on Obesity and Testosterone is…Kind of Fascinating
ACCORDING TO DR. Houman, body fat is actively working to lower T production. Inside fat is an enzyme called aromatase that turns testosterone into estrogen. The increased estrogen sends a message to the brain to ease off signals that keep the testes producing.
To make things worse, added weight increases inflammation. Herbert Ruckle, MD, chair of the department of urology at Loma Linda University Health, says obesity and the constant inflammatory response suppresses the hypothalamic-pituitary gonadal relationship. “This is the brain to testicle stimulation pathway,” he says Dr. Ruckle. Basically, disruption of this brain pathway can slow down or stop testosterone production.
Fat gain also lowers a protein called sex hormone-binding globulin (SHBG), adds Dr. Houman. This controls how much testosterone and estrogen is actively present in the body.
“The testes are usually fine. The fat is the problem,” Dr. Houman explains. “That’s why I get nervous when someone wants to put a heavy guy with a borderline number straight on testosterone. You can spend all your time chasing the symptom and never touch what’s actually causing it.”
How GLP-1s are Switching Up the T Conversation
AS A REFRESHER, GLP-1 agonists mimic the GLP-1 hormone receptor that regulates the way food passes through the stomach. The drugs boost the brain’s energy-burning capabilities and reduce energy-storing, helping you lose weight.
And yes, this medicated weight loss is affecting guys’ T levels—for the better. Dr. Houman says the difference is really a reversal for guys whose low T counts were primarily because of fat gain. Essentially, it’s less aromatase, less estrogen, the brain turning the testosterone production signals back on, leading to a guy making his own testosterone again.
“You’re not putting hormone in. You’re taking away what was holding him down. It’s a real effect, but I’d keep it honest,” he explains. “One study saw a fairly modest bump, something like the low 300s up to the high 360s, while the trials in heavier men with metabolic low T show more. Importantly, the good data don’t show these drugs shutting the system down. The lift seems to come straight from the weight loss.”
Current Research on GLP-1 and Testosterone
A SMALL STUDY published in Endocrine Abstracts showed that semaglutide was more effective than testosterone replacement therapy in improving body composition and increasing testosterone for men with type 2 diabetes.
Another study suggested that the GLP-1 liraglutide improved sex hormone levels and semen quality in obese male mice. The medication also helped them lose weight and improve reproductive functioning.
On the flip side, research published in the Journal of Sexual Medicine showed that men without diabetes who were prescribed semaglutide had a higher rate of developing erectile dysfunction and low testosterone. But the overall rates were still low. Less than 4 percent received a diagnosis of testosterone deficiency, and 1.4 percent had ED.
Still, more research is needed on GLP-1s and testosterone to fully understand the effects, says Michael Wierschem, MD, urologist and founder of Dallas Men’s Health. But he says that so far the risk of low testosterone and erectile dysfunction is low. In other words, it shouldn’t stop guys from asking about or taking the medications, as weight loss offers many other health benefits.
What Happens to the Body on Day One vs After a Year
IF YOU’RE LOOKING for a complete T transformation, we’re sorry to disappoint: you won’t see anything on the first day. Or the first couple weeks. A more realistic timeline is going to be over a couple of months once visceral fat levels go down.
Just make sure it’s fat and not muscles getting depleted. Despite the added testosterone boost, a guy can feel more wiped out early on even when his bloodwork shows he’s headed in the right direction. Dr. Houman warns that a lot of guys don’t see the energy loss coming.
“[Muscle loss] is fixable with enough protein and some lifting, and I bring it up with everybody before they start,” he explains. “We don’t have solid multi-year numbers yet, but I’d bet on the obvious. Keep the weight off and you keep the benefit. Let it creep back and the testosterone goes right back with it.”
What GLP-1 is Best for Boosting Testosterone?
WHILE IT DOES take time to bring testosterone levels back up, another factor is what type of GLP-1 you’re using. Nowadays, there are tons of options available. In terms of testosterone restoration, Dr. Ruckle says the best option is tirzepatide (Mounjaro).
“The speed of restoration generally depends on the speed of action of the GLP-1 drug,” says Dr. Ruckle. “Tirzepatide is the fastest and causes the quickest restoration of testosterone.” Semaglutide (Ozempic), on the other hand, is not the best option since it’s slower and steadier. This translates to a more gradual increase in testosterone.
Dr. Houman acknowledges that there hasn’t been a research study proving one GLP-1 is superior than the others for T count. But from reading the weight and lab numbers, he agrees that tirzepatide beats semaglutide for weight so a bigger testosterone effect is a reasonable expectation.
GLP-1 is not a Testosterone Panacea
OBESITY IS ONE factor that can lower testosterone, and losing weight can typically improve your levels, says Dr. Wierschem.
Taking GLP-1s is one way to help you lose weight, but he says that there are limits. Weight loss while on the drugs can vary, with some people losing as low as five pounds to thirty pounds or higher. Lifestyle changes, like exercise and diet adjustments, also influence results.
“In my clinic, we make sure when we put somebody on semaglutide, we also put them on a diet and exercise plan,” Dr. Wierschem adds. “It’s important to combine all of that. You can’t just take semaglutide and expect to lose 100 pounds.” That said, the initial weight loss (and reduced joint strain) from GLP-1s might motivate you to get back into exercise—another genius way to increase T.
Jocelyn Solis-Moreira, MS is the associate health & fitness for Men’s Health and has previously written for CNN, Scientific American, Popular Science, and National Geographic before joining the brand. When she’s not working, she’s doing circus arts or working towards the perfect pull-up.
Erica Sweeney is a writer who mostly covers health, wellness and careers. She has written for The New York Times, HuffPost, Teen Vogue, Parade, Money, Business Insider and many more.
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