The Real Levers That Move Testosterone
Production, function, and the real levers — for both sexes
Testosterone matters for both men and women — it affects muscle mass, energy, mood, libido, bone density, and cognitive function in both sexes, though normal ranges differ substantially. Levels decline gradually with age in both, but the rate of decline is heavily influenced by lifestyle factors that are genuinely within your control.
Recognising Low Testosterone
Common signs: reduced energy and motivation, lower libido, low mood or irritability, reduced muscle mass despite consistent training, and increased body fat, particularly around the abdomen.
None of these signs is specific to low testosterone on its own — they overlap substantially with poor sleep, depression, and thyroid dysfunction (Section 4). That overlap is exactly why bloodwork, not symptom-matching alone, is what confirms it.
Sleep Is the Single Biggest Lever
In a controlled study, healthy young men restricted to under 5 hours of sleep per night for one week showed testosterone levels 10–15% lower than during a week of adequate sleep — a measurable, meaningful decline from just one week of short sleep in otherwise healthy men[1]. This is a larger effect than most supplements marketed for testosterone claim to produce, and it's free.
Resistance Training's Genuine Hormonal Effect
A comprehensive review of the exercise-endocrinology literature describes a consistent acute hormonal response to resistance training — testosterone and growth hormone both rise in the 15–30 minutes following a session, particularly with protocols using higher volume, moderate-to-high intensity, shorter rest periods, and larger muscle groups[2]. The review is careful to note that this acute post-exercise spike appears more relevant to the tissue-remodelling process than to any lasting change in resting hormone levels — many studies don't find a significant change in baseline testosterone from resistance training despite clear strength and muscle gains, meaning the mechanism is the acute training response itself, not a permanently elevated baseline.
Body Composition: Aromatase and the Fat-Hormone Link
Adipose (fat) tissue contains an enzyme called aromatase that converts testosterone into oestrogen. This is why excess body fat is directly, mechanistically connected to lower testosterone — not just correlated with it through some indirect lifestyle pathway, but literally converting the hormone into a different one at a higher rate. This is also why very low body fat can be problematic in the other direction: the body needs some fat mass to support normal hormone production, and both extremes carry a hormonal cost.
Zinc and Vitamin D: Real but Modest Cofactor Roles
Zinc is a genuine cofactor in testosterone synthesis — a controlled study found that experimentally restricting dietary zinc in young men produced a significant drop in testosterone over 20 weeks, while zinc supplementation in older men with marginal zinc deficiency raised testosterone measurably[3]. Vitamin D's role is more mixed: an early controlled trial found a testosterone increase with vitamin D supplementation in overweight men undertaking a weight-loss program[4], but subsequent trials in broader populations have produced inconsistent results — the honest summary is that correcting a genuine zinc or vitamin D deficiency is a reasonable, low-risk step for someone who has one, but supplementing beyond adequate levels in someone who isn't deficient has considerably weaker support.
Alcohol: More Nuanced Than "Always Lowers It"
A 2024 meta-analysis of the chronic alcohol research found that sustained alcohol consumption reliably reduces free testosterone in men, with heavy, long-term use associated with more severe suppression and, in alcohol dependence, outright hypogonadism — clinically low testosterone — that's often reversible after several weeks of abstinence[5]. The acute, single-dose picture is genuinely different: a controlled crossover trial found that a single low dose of alcohol produced a measurable acute increase in testosterone in men, not a decrease[6]. The honest synthesis: chronic, regular drinking is reliably testosterone-suppressive — the dose-response relationship there is solid — but the flat claim that "even one drink lowers testosterone" doesn't hold up against the acute-dose research, which points the other way for a single low dose specifically.
Tongkat Ali: One of the Better-Evidenced Botanicals in This Space
Tongkat Ali (Eurycoma longifolia) is a herbal extract with a genuinely more substantial human trial base than most botanicals marketed for testosterone. A systematic review and meta-analysis pooling five randomised controlled trials found a significant increase in total testosterone with Eurycoma longifolia supplementation, with the effect present in both healthy volunteers and men with clinically low testosterone[12]. The authors were careful to note real limitations — the pooled trials varied considerably in dose, duration, and population, and the total evidence base remains small. Moderate evidence — better than most botanicals, but well below sleep and resistance training.
Sleep Apnoea's Specific Effect
Beyond the general sleep-restriction effect covered above, sleep apnoea specifically — repeated breathing interruptions during sleep, covered in depth in the Sleep guide — is independently associated with suppressed testosterone in men, plausibly through the same disrupted, fragmented sleep architecture that drives its other health effects. Anyone with suspected sleep apnoea (loud snoring, witnessed breathing pauses, or persistent daytime fatigue despite adequate time in bed) should get it evaluated and treated directly rather than relying on general sleep-hygiene fixes.
Section takeaway
Sleep is the single most reliable, evidenced lever on testosterone available to most people — more consistently supported than most supplements sold for the purpose. Body composition matters mechanistically, not just statistically, via aromatase. The alcohol relationship is dose- and duration-dependent: chronic heavy use suppresses it reliably; a single low dose does not. And among supplements specifically, Tongkat Ali has a meaningfully better trial base than most, even while still falling short of the sleep and training evidence.