Low Testosterone and Weight in Men: What the Evidence Shows

By the Healthy Weight Loss 4 U Clinical Content Team · Published October 20, 2026 · Updated October 20, 2026 · 9 min read

Key takeaways

• Endocrine Society guidance requires symptoms plus unequivocally and consistently low total testosterone, confirmed by repeating a morning fasting measurement; routine screening of the general population is not recommended ^[1].
• In a review of 24 studies, weight loss by low-calorie diet or bariatric surgery was associated with higher testosterone, and the rise was larger with more weight loss ^[9].
• TRAVERSE (5,246 men aged 45 to 80 with testosterone below 300 ng/dL): major cardiovascular events occurred in 7.0% on testosterone gel and 7.3% on placebo (hazard ratio 0.96) ^[5].
• In T4DM, 12% of men on testosterone injections versus 21% on placebo reached the diabetes threshold at 2 years, but hematocrit above 54% occurred in 22% versus 1% ^[6].
• FDA labeling says safety and efficacy in men with age-related hypogonadism have not been established, and in February 2025 the FDA said testosterone is approved solely for men who lack or have low testosterone ^[2][3].

How is low testosterone diagnosed in men?

Low testosterone (hypogonadism) is diagnosed when a man has both symptoms and consistently low blood testosterone, not from symptoms alone or from a single result. The Endocrine Society 2018 guideline recommends diagnosing testosterone deficiency only in men with symptoms and signs of deficiency and unequivocally and consistently low serum total testosterone, with the diagnosis confirmed by repeating a morning fasting total testosterone measurement ^[1].

The same guideline recommends accurate assays and rigorously derived reference ranges, and measuring luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to distinguish testicular from pituitary or hypothalamic causes ^[1]. It recommends against routine screening of the general population ^[1]. The guideline page does not give a single numeric cutoff, so the lower limit of normal depends on the laboratory's reference range ^[1].

FDA-approved testosterone labels use similar wording. The AndroGel label says to confirm the diagnosis of hypogonadism before starting treatment, with testosterone measured in the morning on at least two separate days and below the normal range ^[3]. The XYOSTED label, revised July 2025, says the same ^[4].

Clinical trials set their own entry rules. TRAVERSE, discussed below, enrolled men with symptoms of hypogonadism and two fasting testosterone levels below 300 ng/dL ^[5]. That is a study criterion, not a universal diagnostic line.

How are obesity and testosterone related?

Obesity and low testosterone are linked, and the best evidence is that losing weight is associated with higher testosterone, but the studies cannot show which way cause runs in every man. About 41.9% of US adults aged 20 and over had obesity in 2017 to March 2020, so many men who ask about testosterone also have excess weight ^[10].

A systematic review and meta-analysis in the European Journal of Endocrinology pooled 24 studies of weight loss by diet or bariatric surgery. It found that weight loss was associated with an increase in both bound and unbound testosterone, with a larger increase after bariatric surgery than after low-calorie diets, and with lower estradiol and higher gonadotropins ^[9]. The rise was larger in men who lost more weight, and the amount of weight lost was the strongest predictor of the testosterone increase ^[9].

The review also found larger testosterone increases in younger men, in men without diabetes and in men with more severe obesity ^[9]. These are associations from pooled studies of mixed design, not proof that weight loss cures a medical diagnosis of hypogonadism.

Obesity can also interact with treatment safety. The AndroGel label notes that testosterone may worsen sleep apnea, especially in men with obesity or chronic lung disease ^[3]. The Endocrine Society guideline lists untreated severe obstructive sleep apnea among the conditions that argue against starting testosterone ^[1].

What did the TRAVERSE trial show about heart safety?

TRAVERSE showed that, in men with diagnosed hypogonadism and high cardiovascular risk, testosterone gel did not increase major cardiovascular events compared with placebo, while it did increase some other adverse events. It was a multicenter, randomized, double-blind, placebo-controlled noninferiority trial of 5,246 men aged 45 to 80 with preexisting cardiovascular disease or high cardiovascular risk, symptoms of hypogonadism and two fasting testosterone levels below 300 ng/dL ^[5].

The primary outcome, a composite of cardiovascular death, nonfatal heart attack or nonfatal stroke, occurred in 182 men (7.0%) on testosterone and 190 men (7.3%) on placebo (hazard ratio 0.96, 95% confidence interval 0.78 to 1.17), which met the prespecified noninferiority margin ^[5]. Mean age was 63.3 years and mean BMI was about 35, so the men were typically older and living with obesity ^[5]. The study was published in the New England Journal of Medicine in 2023 and was funded by AbbVie and others ^[5].

The authors said the increases in atrial fibrillation and acute kidney injury were not expected ^[5]. They also listed limits: about 61% of men in each group stopped their assigned treatment, 20.8% withdrew before the end-of-trial visits, informative censoring could not be ruled out, and the article did not assess whether testosterone relieved symptoms or changed other outcomes ^[5]. Secondary endpoints were not adjusted for multiple comparisons ^[5].

TRAVERSE did not test weight loss as a goal. It tested safety in men who already met a hypogonadism definition.

What did the T4DM trial test, and did it measure weight?

T4DM tested whether testosterone injections could prevent or reverse type 2 diabetes in men who were overweight or obese, and the main result concerned diabetes, not body weight. It was a 2-year, double-blind, placebo-controlled phase 3b trial at six Australian centers, published in The Lancet Diabetes and Endocrinology in 2021 ^[6].

Men were aged 50 to 74, had overweight or obesity and either impaired glucose tolerance or newly diagnosed type 2 diabetes, and all joined a lifestyle program ^[6]. In all, 1,007 men were randomized to testosterone undecanoate injections or placebo ^[7]. The abstract describes the men as having low testosterone ^[6], though the later follow-up authors characterize them as men without pathological hypogonadism ^[7]. That distinction matters when applying the results.

At 2 years, 12% of men on testosterone versus 21% on placebo reached the diabetes threshold on an oral glucose tolerance test (relative risk 0.59) ^[6]. Safety findings included a hematocrit above 54% in 22% of the testosterone group versus 1% of placebo, which the authors suggested may limit treatment, and serious adverse events in 10.9% versus 7.4% ^[6]. The authors concluded that longer-term durability and cardiovascular safety remained unknown ^[6]. Funders included Bayer, Eli Lilly, WW and Australian public bodies ^[6].

A follow-up survey (JCEM, 2023) reached 599 of the 1,007 men a median of 5.1 years after their last injection. Self-reported new diabetes, prostate disease and cardiovascular disease did not differ between groups, and neither did weight maintenance or weight-loss behaviors. New sleep apnea diagnoses were more common on testosterone during the study (3.0% versus 0.4%), and more men in the testosterone group later resumed prescribed testosterone (6% versus 2.8%) ^[7]. The follow-up was an observational email survey, so it is weaker evidence than the trial itself ^[7].

Does testosterone treatment cause weight loss?

No trial reviewed here shows that testosterone causes weight loss, and the best-controlled study found a change in body composition, not a proven change in the scale. In a randomized, double-blind trial in BMC Medicine, 100 men with obesity (BMI of 30 or higher), total testosterone of 12 nmol/L or less and a median age of 53 were assigned to testosterone undecanoate injections or placebo for 56 weeks. All followed a 10-week very low energy diet, then 46 weeks of weight maintenance. Eighty-two completed the study ^[8].

Fat mass fell more with testosterone, with a mean adjusted between-group difference of 2.9 kg (95% confidence interval 0.2 to 5.7 kg; P = 0.04), and visceral fat also fell more ^[8]. Both groups lost similar lean mass during the diet. During maintenance, the testosterone group regained 3.3 kg of lean mass, and by the end its lean mass loss was 3.4 kg smaller than with placebo (P = 0.002) ^[8]. The authors wrote that the weight loss with testosterone was almost exclusively fat ^[8].

Read that carefully. The fat-mass confidence interval runs close to zero, the trial was small and the testosterone effect was measured on top of a very low energy diet, so it does not show that testosterone alone causes weight loss. The abstract also did not report body weight as a separate outcome ^[8]. The T4DM follow-up found no difference in weight maintenance or weight-loss behaviors five years later ^[7].

Labels reflect this. The AndroGel indication is replacement therapy in adult males with a deficiency or absence of endogenous testosterone, and weight loss is not an indication ^[3].

What does FDA labeling say about indications and risks?

FDA labeling says testosterone is for men with a deficiency or absence of testosterone due to a medical condition, not for the decline that comes with aging. The AndroGel label (revised October 2025) is indicated for replacement therapy in adult males with a deficiency or absence of endogenous testosterone, including primary and hypogonadotropic hypogonadism, and states that safety and efficacy in men with age-related hypogonadism have not been established ^[3]. The XYOSTED label (July 2025) repeats that limitation ^[4].

On February 28, 2025, the FDA announced class-wide changes for all testosterone products. It said testosterone remains approved solely for men who lack or have low testosterone, retained the Limitation of Use for age-related hypogonadism, removed cardiovascular-risk language from the Boxed Warning, added the TRAVERSE results to all labels and added a warning about increased blood pressure, after ambulatory blood pressure monitoring studies confirmed a rise with all testosterone products ^[2].

Other label warnings include the following:

• Blood pressure: the gel can increase blood pressure and is not recommended for men with uncontrolled hypertension ^[3].
• Polycythemia: hematocrit should be checked before starting and rechecked periodically because increased red cell mass may raise thromboembolic risk ^[3].
• Venous thromboembolism: the label reports 1.7% on gel versus 1.2% on placebo in TRAVERSE ^[3].
• Sleep apnea and prostate: testosterone may worsen sleep apnea, and prostate cancer should be evaluated before and during treatment ^[3].
• Secondary exposure: the AndroGel boxed warning concerns virilization in children exposed to the gel ^[3].

The Endocrine Society guideline adds that men planning fertility soon, men with breast or prostate cancer and men with elevated hematocrit should not be treated, and it suggests against using testosterone for glycemic control in men with type 2 diabetes ^[1].

What does the evidence not show?

Several gaps matter for anyone weighing testosterone against other approaches to weight and metabolic health.

• No randomized trial reviewed here shows that testosterone causes weight loss in men ^[7][8].
• TRAVERSE tested cardiovascular safety in men with diagnosed hypogonadism and did not assess symptom benefit ^[5].
• T4DM measured diabetes progression in a lifestyle program, and about 5 years after treatment, self-reported new diabetes did not differ between groups ^[6][7].
• The weight-loss and testosterone link comes from pooled studies and is an association ^[9].
• Long-term results at 5 years in T4DM relied on self-report from 599 of 1,007 men ^[7].
• Results from one product and route, such as a gel or an injection, may not carry over to another product, and labels differ by product ^[3][4].

Evidence on safety also has limits. TRAVERSE averaged 33 months of follow-up, and a majority of men stopped their assigned treatment before the end ^[5].

What this means in practice

• A diagnosis requires symptoms plus consistently low morning testosterone on repeat testing; one low result or one symptom is not enough ^[1][3].
• Excess weight and low testosterone often travel together, and in pooled studies weight loss was associated with higher testosterone, so weight and testosterone are best evaluated together ^[9].
• Testosterone is labeled for men with a medical cause of deficiency, not for age-related decline and not for weight loss ^[2][3].
• TRAVERSE found no excess in major heart events but did find more atrial fibrillation, kidney injury and pulmonary embolism, and the FDA now warns about blood pressure increases ^[2][5].
• The T4DM diabetes result applies to a specific group and was accompanied by high hematocrit in 22% of treated men ^[6].
• Sleep apnea, prostate health, hematocrit and fertility plans should be reviewed before any hormone therapy is considered ^[1][3].
• Labels, not marketing claims, define what has been studied for each testosterone product, and results from one product or route may not carry over to another ^[3][4].

When to talk to a clinician

Fatigue, low drive, weight gain and low mood can come from many causes, including sleep problems, thyroid conditions, depression, medications and excess weight itself, so they do not on their own mean testosterone is low. Whether testing makes sense, how to interpret repeat morning results and what the alternatives are depend on your history, and only a licensed clinician can decide that after an evaluation.

At Healthy Weight Loss 4 U, every program begins with a clinician evaluation, and that evaluation is where to raise questions about low testosterone, symptoms and your weight history. Bring a list of your symptoms, your medications and any previous lab results. If you have chest pain, sudden shortness of breath, leg swelling or severe headache, seek urgent medical care.

Frequently asked questions

Sources

1. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline (J Clin Endocrinol Metab 2018), guideline summary. Endocrine Society, 2018. www.endocrine.org/clinical-practice-guidelines/testosterone-therapy
2. FDA issues class-wide labeling changes for testosterone products. U.S. Food and Drug Administration, 2025. www.fda.gov/drugs/drug-alerts-and-statements/fda-issues-class-wide-labeling-changes-testosterone-products
3. ANDROGEL (testosterone) gel, prescribing information (revised 10/2025). DailyMed, U.S. National Library of Medicine, 2025. dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f4e8d29b-8707-4d47-e053-2a95a90aecee
4. XYOSTED (testosterone enanthate) injection, prescribing information (07/2025). U.S. Food and Drug Administration, 2025. www.accessdata.fda.gov/drugsatfda_docs/label/2025/209863s020lbl.pdf
5. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE), N Engl J Med 2023;389(2):107-117. New England Journal of Medicine, 2023. doi.org/10.1056/NEJMoa2215025
6. Testosterone treatment to prevent or revert type 2 diabetes in men enrolled in a lifestyle programme (T4DM): a randomised, double-blind, placebo-controlled, 2-year, phase 3b trial, Lancet Diabetes Endocrinol 2021;9(1):32-45. The Lancet Diabetes & Endocrinology (record via University of Adelaide), 2021. eres.library.adelaide.edu.au/dspace/handle/2440/129790
7. Long-Term Outcomes of Testosterone Treatment in Men: A T4DM Post-Randomisation Observational Follow-Up Study, J Clin Endocrinol Metab 109(1). Journal of Clinical Endocrinology and Metabolism (record via Austin Health), 2023. ahro.austin.org.au/austinjspui/handle/1/33606?mode=full
8. Effects of testosterone treatment on body fat and lean mass in obese men on a hypocaloric diet: a randomised controlled trial, BMC Medicine 14:153. BMC Medicine (record via Monash University), 2016. research.monash.edu/en/publications/effects-of-testosterone-treatment-on-body-fat-and-lean-mass-in-ob/
9. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis, Eur J Endocrinol 168(6):829-43. European Journal of Endocrinology (PubMed), 2013. pubmed.ncbi.nlm.nih.gov/23482592/
10. Adult Obesity Facts. Centers for Disease Control and Prevention, 2024. www.cdc.gov/obesity/adult-obesity-facts/index.html

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