Low testosterone is common in men who are overweight or obese, and excess weight can be part of the reason.
That raises an important question: if weight is contributing, can losing weight raise testosterone enough to avoid or delay testosterone replacement therapy?
Sometimes it can. In other men, the improvement is more modest and TRT may still be the right choice.
Why excess weight can lower testosterone
Extra body fat, particularly around the abdomen, is linked with insulin resistance, low-grade inflammation and changes in the hormonal signals travelling from the brain to the testicles. These changes can reduce testosterone production.
Fat tissue also converts some testosterone into oestrogen, which can further suppress the signals that drive testosterone production.
The overall result can be what doctors call functional low testosterone. The testicles may still be capable of producing testosterone, but the signals driving them are reduced. If weight and metabolic health improve, testosterone production may recover.
Obesity also tends to lower SHBG, the protein that carries much of the testosterone in the blood. When SHBG is low, total testosterone can appear lower even when free testosterone has fallen by less. This is why total testosterone should not be interpreted on its own.
Interpreting a low testosterone result
Before assuming that weight is the main cause, it is important to confirm the result and look at the wider picture.
Testosterone varies naturally and is highest in the morning. It can also fall temporarily during illness, poor sleep and other periods of physiological stress. A low result should therefore usually be repeated on a separate morning.
Other blood tests help show where the problem may lie. These usually include LH and FSH, the signalling hormones that stimulate the testicles, along with SHBG and prolactin.
Other factors can contribute too, including previous anabolic steroid or SARM use, untreated sleep apnoea, heavy alcohol use, some prescribed medicines, previous testicular injury, undescended testicles, chemotherapy or problems with puberty.
Often there is no single cause. Weight, sleep, alcohol, metabolic health and age may all be contributing at the same time.
How much can weight loss actually help testosterone levels?
The evidence is fairly consistent. Testosterone rises as men lose weight, and the more weight lost, the greater the rise tends to be.
A review of 44 studies involving more than 1,700 men gives a useful sense of scale. Men who lost weight through diet gained, on average, around 2.5 nmol/L of total testosterone. Men who had weight-loss surgery, and therefore lost much more weight, gained around 7 nmol/L. The men who gained the most tended to be those who started with the highest weight and the lowest testosterone levels.
These are averages, so not everyone will see the same change.
It is also worth knowing that quite substantial weight loss may sometimes be needed before the difference becomes clinically meaningful. British Society for Sexual Medicine guidance cites data from the European Male Ageing Study in which around a 20% reduction in BMI was needed before free testosterone increased significantly or erectile function improved meaningfully. That is a substantial amount of weight to lose, and for many people it can be difficult to achieve and maintain without additional support. The same guidance notes that smaller amounts of weight loss can still raise testosterone, but the effect may be modest.
If testosterone is only moderately low, a rise of 2 or 3 nmol/L may be enough to make a meaningful difference and, more importantly, improve symptoms.
If testosterone is very low, for example around 5 or 6 nmol/L, a rise of 2 or 3 may still leave it below the normal range. Weight loss is still worth doing, but it may not be enough on its own.
Why weight loss first can sometimes make sense
Fertility is one of the main reasons.
Testosterone replacement suppresses LH and FSH, the hormones that help drive sperm production, and this can reduce sperm counts substantially. If there is any chance you may want children, this needs to be discussed before treatment is started.
In some men, hCG is used alongside TRT to support testicular function and try to preserve fertility, although this approach does not guarantee fertility.
Where excess weight is a major contributor to low testosterone, improving weight first gives the body a chance to recover its own production without needing to suppress the hormonal axis in the first place.
TRT also suppresses your own testosterone production while you are taking it and requires ongoing monitoring. That is not a reason to avoid treatment if it is needed, but it is a reason to consider whether a reversible cause can be addressed first.
What about weight-loss medicines?
Newer medical weight-management treatments can produce substantial weight loss, and early studies suggest testosterone may improve alongside this. These treatments are aimed at obesity and metabolic health rather than low testosterone, so any rise in testosterone is likely to be a secondary effect of the weight loss and metabolic improvement. We are experts on weight loss management and can help advise on this where required.
Can weight loss and TRT be addressed at the same time?
Yes.
If testosterone is genuinely low, symptoms are significant, and weight loss alone is unlikely to raise it enough, TRT can still be considered while weight is being addressed.
Starting TRT does not make the weight problem any less important. Both can be treated at the same time.
TRT can improve body composition in men with testosterone deficiency, increasing lean mass and reducing fat mass. Some men also find that feeling better makes exercise easier to sustain.
But TRT is not a treatment for obesity. Its role is to treat testosterone deficiency, while weight management addresses the underlying weight and metabolic issues.
What should be considered before TRT?
Before starting TRT, the low testosterone result should be confirmed and interpreted alongside SHBG, LH and FSH. Other possible contributors, including previous steroid or SARM use, sleep apnoea, alcohol, medication and previous testicular problems, should also be considered.
Fertility plans are also important before deciding whether TRT is appropriate.
The bottom line
Losing weight can raise testosterone, and the more weight lost, the greater the improvement tends to be.
If testosterone is only moderately low, weight loss may improve it enough to change whether treatment is needed. But meaningful improvements in free testosterone and sexual symptoms may require substantial weight loss, and if testosterone is very low, weight loss may help without being enough on its own.
For younger men, and for anyone thinking about fertility, there is more reason to see what weight loss can achieve before starting testosterone treatment.
For others, TRT can be considered while weight management continues.
The aim is to work out how much of the low testosterone is likely to be reversible, and whether weight loss alone is likely to be enough.
If you want to learn more around this subject, then contact us or check out our TRT and weight loss management services for more information.
References
- Ken-Dror G, Fluck D, Fry CH, Han TS. Meta-analysis and construction of simple-to-use nomograms for approximating testosterone levels gained from weight loss in obese men. Andrology. 2024;12(2):297–315. doi:10.1111/andr.13484.
- Hackett G, Kirby M, Rees RW, et al. The British Society for Sexual Medicine guidelines on male adult testosterone deficiency, with statements for practice. World J Mens Health. 2023;41(3):508–537. doi:10.5534/wjmh.221027.
