Weight loss does raise testosterone, and the trial evidence still does not put a GLP-1 among the strategies shown to do it. A network meta-analysis of 23 randomized trials in 1,899 men with obesity-related low testosterone tested five strategies, and GLP-1-based therapy was one of them [1]. The increases it reports as significant belong to testosterone replacement with lifestyle therapy at MD 7.19, endogenous restoration at 4.14 and replacement alone at 2.53. The only randomized head-to-head enrolled 25 men for 24 weeks, and total testosterone rose in both arms [2]. Nobody selling these drugs online measures the hormone, which is the gap running through the sexual-function evidence as well.
What was compared
Randomized trials of structured lifestyle therapy, testosterone replacement, endogenous testosterone restoration, GLP-1-based therapy, or testosterone replacement combined with structured lifestyle therapy, searched to April 2026. [1] Twenty-three trials and 1,899 participants went into a frequentist network, with risk of bias assessed by RoB 2 and confidence in each comparison graded by CINeMA.
Against usual care or placebo, testosterone replacement plus lifestyle therapy produced the largest increase in total testosterone, MD 7.19, 95% CI 1.18 to 13.21. Endogenous restoration followed at 4.14, 95% CI 0.74 to 7.54, and testosterone replacement alone at 2.53, 95% CI 0.26 to 4.81.
The one randomized comparison, and why it flatters the drug
Twenty-five men with type 2 diabetes, obesity and functional hypogonadism were randomized to semaglutide 1 mg weekly or intramuscular testosterone undecanoate for 24 weeks, open-label [2]. Total testosterone rose in both arms, and both improved on the Aging Symptoms scale, while only the testosterone arm improved significantly on erectile function. The semaglutide arm beat a comparator that suppresses sperm production, which is a lower bar than the headline suggests, and the full reading of that trial sits in the fertility evidence.
The nearest thing to an outcome
Testosterone is a blood test, and the symptom most men actually bring in is erectile function. A retrospective cohort in the TriNetX network compared men aged 18 to 70 with type 2 diabetes and no prior erectile dysfunction, in three propensity-matched pairings. Tirzepatide was associated with a lower risk of a diagnosis or a PDE-5 prescription [3]. Against sitagliptin the risk ratio was 0.70 (95% CI 0.64 to 0.76), against injectable semaglutide 0.67 (0.62 to 0.72), and against dulaglutide 0.55 (0.51 to 0.59). Its authors say randomized trials are needed to confirm it, and nothing in it measures the hormone itself.
The outcomes disagree with each other
Testosterone replacement plus lifestyle therapy was the only strategy that significantly improved erectile function on the International Index of Erectile Function, MD 1.29, 95% CI 0.07 to 2.50 — an interval that barely clears zero.
Testosterone replacement alone reduced waist circumference and increased lean mass. It also increased hematocrit, which is the classic reason testosterone requires monitoring. Endogenous restoration and the combination also increased lean mass. And no intervention at all significantly reduced glycated hemoglobin.
So the question “which treatment is best” has no answer here, and not for the usual reason. It is not that the evidence is too thin to separate them — though confidence in many comparisons was graded low or very low. It is that they genuinely do different things, and which one is best depends entirely on which symptom brought somebody in.
Why that is the useful finding
Because a man with obesity and low testosterone is usually presented with one option by whoever he happens to consult. A urologist reaches for testosterone. A weight clinic reaches for a GLP-1. A primary care physician reaches for lifestyle advice. Each is defensible and none is complete.
The authors say explicitly that their findings should inform individualized decisions rather than a definitive ranking, and that longer head-to-head trials are needed. That is the correct conclusion from an analysis where the winner changes with the outcome — and it is a different situation from a comparison too small to find a difference.
What it means for someone buying online
Nobody on this roster treats hypogonadism, and no seller here measures testosterone. What they sell is weight loss, and weight loss genuinely helps obesity-related low testosterone — that is why the condition is called functional and reversible.
If low testosterone is the reason somebody is considering a weight-loss drug, that is a conversation for a clinician who will measure it before and after, and repeat it. What a seller asks about before shipping is measurably little, and the same silence covers the menopause question set out in the subgroup nobody reported.