Male hypogonadism caused by organic disease of the brain’s reproductive control centers or of the testes affects less than 1% of men. Low testosterone attributable to obesity, defined as a body-mass index of 30 or above, runs 2% to 8%. Diagnosis requires symptoms plus a consistently low morning serum testosterone — under 264 to 300 ng/dL in at least two fasting samples drawn between 7 and 10 a.m. on a quality-controlled assay — and in men with obesity a calculated free testosterone is necessary rather than optional, because obesity lowers sex hormone-binding globulin.[1]
That last clause is the whole subject. It is also the clause a telehealth upsell does not mention.
Why the number is low, and what kind of low it is
A 2025 clinical review sets out the distinction plainly. Obesity-related reductions in SHBG, testosterone’s principal circulating carrier protein, are primarily responsible for the measured reduction in total testosterone. Proportionately reduced testosterone and SHBG alongside normal luteinizing hormone and follicle-stimulating hormone describe a eugonadal state, which the review names the pseudo-hypogonadism of obesity. In the absence of pathological hypogonadism, testosterone treatment is less effective than a diet and lifestyle intervention at correcting the reversible conditions producing the symptoms, so it is not indicated — and unwarranted off-label treatment can cause infertility, a hematocrit high enough to require venesection, a prothrombotic state and testosterone dependence.[2]
So a man with obesity, fatigue, low libido and a total testosterone of 250 ng/dL has a finding that in most cases reverses with the weight. Fatigue in particular has several competing explanations on this drug, collected in the fatigue article. Whether the drug that removes the weight also does something to the testis is a separate question, and a narrower one than it is usually sold as.
What weight loss alone does
A meta-analysis of 24 studies of diet and bariatric surgery found both raise bound and unbound testosterone significantly (P < 0.0001 for each), with the surgical effect roughly three times the low-calorie-diet effect. The androgen rise was larger in men who lost more weight, in younger men, in men without diabetes and in men with more severe obesity, and multiple regression identified the degree of weight loss as the best determinant of the rise (B = 2.50 ± 0.98, P = 0.029).[3] The 2026 review puts the clinical threshold at 5%: weight loss of at least that much typically increases total testosterone significantly, and is associated with improved physical function, libido and erectile function.[1]
What the incretin class adds, measured directly
A 2025 systematic review and meta-analysis pooled seven studies covering 680 men. Treatment produced a significant increase in total serum testosterone — a standardized mean difference the authors report as 1.39 ng/mL (95% CI, 0.70 to 2.09; P < 0.0001) — with free testosterone, SHBG, LH and FSH all rising and weight, BMI, waist circumference and HbA1c all falling. Two findings inside it matter more than the headline. Meta-regression found a significant negative correlation between the testosterone change and the percentage change in weight and BMI, meaning the hormone tracked the weight. And against other treatments, this class showed a comparable effect on serum androgens with a greater reduction in BMI. The authors state that the limitations of the literature do not allow a direct action on testicular function to be demonstrated.[4]
A 2026 systematic review of ten studies in 639 men adds the qualification that changes the reading. Total testosterone rose consistently, particularly in men with obesity, type 2 diabetes or functional hypogonadism. Free testosterone changes were inconsistent, often offset by concurrent rises in sex hormone-binding globulin. LH and FSH were preserved or increased — in contrast to the suppression seen in the testosterone-therapy comparator arms — and semen parameters improved in men with obesity or hypogonadism but not in healthy men.[5]
Put beside the mechanism, that is coherent rather than disappointing. Obesity depresses total testosterone largely by depressing SHBG; losing weight raises SHBG; total testosterone rises with it. The biologically active fraction is the one that does not reliably follow. A lab report showing a total testosterone up 90 points is consistent with a free testosterone that has barely moved.
The result that reverses direction
A prospective cohort followed 51 men with type 2 diabetes starting a GLP-1 receptor agonist. Over six months they lost 2.27 kg (p = 0.00162) and improved HbA1c by 0.7 points (p = 0.000503). For the group as a whole there was no significant change in testosterone. Split by baseline, the direction reversed: in men starting below 320 ng/dL total testosterone rose from 238.5 ± 56.5 to 272.2 ± 82.3 ng/dL, while in men starting above it the level fell from 438 ± 98.2 to 412 ± 141.2 (p = 0.0172). Free testosterone did the same, rising from 55.2 to 57.2 pg/mL in the lower group and falling from 74.7 to 64.2 pg/mL in the higher one (p = 0.00807). Men whose HbA1c improved by at least a point gained testosterone; men whose glucose barely moved lost a little.[6]
That is the finding that resists the obvious reading. This is not a drug that raises testosterone. It is a drug that removes a suppressor of testosterone, and it does nothing for a man who was not suppressed.
Against testosterone itself
Two randomized head-to-head studies exist and both are small. A 16-week open-label trial randomized 30 men with obesity-associated functional hypogonadism, mean BMI 41.2, to liraglutide 3.0 mg daily or 1% transdermal testosterone gel. Total testosterone rose in both arms (+5.9 ± 7.2 nmol/L on testosterone against +2.6 ± 3.5 on liraglutide) and sexual function improved in both. Liraglutide significantly raised LH and FSH (P < 0.001 for the between-treatment effect), and produced 7.9 ± 3.8 kg of weight loss against 0.9 ± 4.5 kg.[7]
The second is the one a man considering a bundled program needs. A 24-week randomized open-label trial in 25 men with type 2 diabetes, obesity and functional hypogonadism compared semaglutide 1 mg weekly with intramuscular testosterone undecanoate. Baseline semen quality was poor in both arms. On semaglutide, morphologically normal sperm rose from 2% to 4% (p = 0.012). On testosterone, sperm concentration and total sperm number fell significantly. Both arms raised total testosterone and improved the Aging Males’ Symptoms score; only testosterone improved the erectile function questionnaire.[8]
That is a genuine trade rather than a ranking, and twenty-five men is not enough to settle it. What it does establish is that the two products sold side by side on the same checkout page do opposite things to fertility.
Where this class ranks when everything is compared at once
A 2026 network meta-analysis assembled 23 randomized trials and 1,899 men with obesity-related functional hypogonadism, comparing structured lifestyle therapy, testosterone replacement, endogenous testosterone restoration, GLP-1-based therapy and testosterone plus lifestyle. Against usual care or placebo, the interventions that significantly increased total testosterone were testosterone plus lifestyle (MD 7.19; 95% CI, 1.18 to 13.21), endogenous testosterone restoration (4.14; 0.74 to 7.54) and testosterone alone (2.53; 0.26 to 4.81). GLP-1-based therapy is a node in that network and is not among them. Only testosterone plus lifestyle significantly improved the erectile function score (1.29; 0.07 to 2.50). No intervention reduced HbA1c against usual care. Testosterone reduced waist circumference and increased lean mass while increasing hematocrit. Confidence in many comparisons was low or very low, and the authors decline to publish a ranking.[9]
A pilot went the other way and is smaller still: ten men with functional hypogonadism who had lost under 5% of body weight after three months of tirzepatide were allocated five and five to tirzepatide alone or tirzepatide plus testosterone undecanoate. At six months the combination arm recovered lean mass (66.1 ± 3.1 against 63.4 ± 3.0 kg, P < 0.01) while the monotherapy arm continued to lose it, with better HOMA-IR and erectile function scores.[10] Five men per arm is a hypothesis. The lean-mass question it points at is covered properly in the muscle-loss article and in the body-composition article.
What the testosterone label actually says
Testosterone cypionate is indicated for replacement therapy in men with primary hypogonadism from testicular failure — cryptorchidism, torsion, orchitis, vanishing testis syndrome, orchidectomy — or hypogonadotropic hypogonadism from gonadotropin or LHRH deficiency, or from injury to the brain’s hormonal control centers caused by tumors, trauma or radiation. Its label then states that safety and efficacy in men with “age-related hypogonadism”, also called “late-onset hypogonadism”, have not been established. Obesity-related low testosterone is not on the list either.[11]
The same label describes the mechanism a prescriber should be raising: during exogenous administration of androgens, endogenous testosterone release is inhibited through feedback inhibition of luteinizing hormone, and at large doses spermatogenesis may also be suppressed through feedback inhibition of follicle-stimulating hormone. Reported adverse reactions include oligospermia, testicular atrophy, subfertility and infertility.[11] The incretin trials above recorded the opposite pattern on gonadotropins, which is the single clearest difference between the two options.
What this means at a checkout
Sixteen of the 277 sellers written up here run a testosterone or hormone program alongside the GLP-1 one, and some position the pair as a single men’s protocol. Nothing above makes that combination wrong; a man with genuine pathological hypogonadism needs replacement whatever his weight is doing. What it makes is two decisions, the second of which turns on a diagnosis that requires two morning fasting samples, a calculated free testosterone, and LH and FSH measured to separate primary from secondary — none of which a checkout flow performs. The wider question of how thoroughly these intakes assess anything is in the red-flags article, and the individual write-ups are in the provider reviews.
Two further cautions belong to the prescriber. A man who wants children in the foreseeable future is choosing between a drug that improved sperm morphology in a 25-man trial and one whose label lists infertility as an adverse reaction. And a man whose testosterone is normal has no measured benefit to gain: in the cohort above, free testosterone fell in exactly that group.
No GLP-1 receptor agonist is approved for low testosterone by any regulator, and none of the trials above used compounded product. Most sellers here dispense compounded semaglutide or tirzepatide, which are not FDA-approved and are not reviewed by the FDA for safety, efficacy or quality before they are dispensed. The dose in a compounded vial is the dose a compounder prepared, which matters more than usual when a second hormone is being titrated against it — see what a compounded vial contains. The rest of what is and is not different for men is in the men’s health article.