Fat Lowers Testosterone, Low Testosterone Favours Fat. Where Do You Intervene?

Adiposity is associated with lower testosterone, and lower testosterone is associated with changes in body composition that favour further adiposity. Described as a loop it sounds inevitable. Described accurately, it is a set of unresolved questions — which is how a 2018 review in Clinical Endocrinology frames the subject of hypogonadism and male obesity: focus on unresolved questions.[1]

That title is doing something unusual and useful. It refuses to present the loop as settled.

The two arms of the loop

Adiposity → lower testosterone. Adipose tissue expresses aromatase, converting testosterone to estradiol, and obesity alters SHBG, changing how much testosterone is free. The androgen–obesity relationship is well reviewed.[2]

Lower testosterone → adiposity. Testosterone influences body composition. In the dose-response data, fat mass was negatively correlated with testosterone concentration while fat-free mass rose with it.[3]

Each arm has support. What does not follow is that the loop is self-reinforcing in any individual, or that it has a single entry point.

What the intervention evidence shows

The best-controlled look at the composition arm comes from a randomised trial of testosterone treatment in obese men on a hypocaloric diet, which examined effects on body fat and lean mass.[4] Testosterone's effect on body composition is real and measurable.

Two caveats keep that in proportion:

Composition is not the same as metabolic health. Changing fat and lean mass does not automatically translate into the outcomes that matter — and TRAVERSE, the largest trial, found testosterone non-inferior to placebo for major adverse cardiac events rather than protective.[5]

Timing is slow. Fat mass, lean mass and strength change at 12–16 weeks and stabilise at 6–12 months.[6]

What the guideline says to do

Establish the cause. The recommendation is additional diagnostic evaluation to ascertain the cause of a confirmed androgen deficiency before treating.[7] Where adiposity is a major contributor, that is the finding — and it is one with treatments of its own.

This is not an argument against testosterone therapy for men who meet the criteria. It is an argument against treating a hormone level as though it arrived from nowhere.

Frequently asked questions

Will TRT help me lose weight? Testosterone affects body composition,[3][4] which is not the same as being a weight-loss treatment. See does TRT fix obesity.

Will losing weight raise my testosterone? The relationship is documented; the questions about intervention remain explicitly unresolved.[1]

Which should I treat first? A clinical judgement that depends on your numbers, symptoms and what the cause investigation finds.[7]

Is my low testosterone "real" if obesity caused it? The reading is real. Whether it meets the diagnostic definition depends on symptoms plus confirmed consistently low concentrations,[7] and the cause changes what the right response is.

Next in this series

If the loop is real, the obvious question is whether treating one arm fixes the other. That has been studied.

Continue with does TRT fix obesity.

References

7 sources

1. Grossmann M. Hypogonadism and male obesity: Focus on unresolved questions. Clin Endocrinol (Oxf). 2018;89(1):11–21. doi:10.1111/cen.13723 · PMID 29683196
2. Allan CA, McLachlan RI. Androgens and obesity. Curr Opin Endocrinol Diabetes Obes. 2010;17(3):224–232. doi:10.1097/MED.0b013e3283398ee2 · PMID 20418719
3. Bhasin S, Woodhouse L, Casaburi R, et al. Testosterone dose-response relationships in healthy young men. Am J Physiol Endocrinol Metab. 2001;281(6):E1172–E1181. doi:10.1152/ajpendo.2001.281.6.E1172 · PMID 11701431
4. Ng Tang Fui M, Prendergast LA, Dupuis P, et al. Effects of testosterone treatment on body fat and lean mass in obese men on a hypocaloric diet: a randomised controlled trial. BMC Med. 2016;14(1):153. doi:10.1186/s12916-016-0700-9 · PMID 27716209
5. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107–117. doi:10.1056/NEJMoa2215025 · PMID 37326322
6. Saad F, Aversa A, Isidori AM, et al. Onset of effects of testosterone treatment and time span until maximum effects are achieved. Eur J Endocrinol. 2011;165(5):675–685. doi:10.1530/EJE-11-0221 · PMID 21753068
7. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744. doi:10.1210/jc.2018-00229 · PMID 29562364