Testosterone and Training After 40: What Actually Moves the Needle

Testosterone is the topic where the gap between the evidence and the marketing is widest.

On one side you’ve got a supplement industry selling “test boosters” made of tribulus and zinc, and clinics offering replacement therapy on the back of a five-minute online questionnaire. On the other, you’ve got men in their forties who genuinely feel flat, tired and softer than they used to, being told it’s just age and to get on with it.

The reality sits between the two, and it’s more actionable than either. Here’s what’s actually true, what actually raises testosterone, and when it’s worth seeing a doctor rather than buying a powder.

A note before we start: I’m not a doctor, and nothing here is medical advice. If you have symptoms that concern you, get a blood test through your GP.

What Actually Happens to Testosterone After 40

Total testosterone declines roughly 1% per year from your thirties onward. That’s the widely cited figure and it’s broadly right.

Put in context: a 30-year-old with a level of 600 ng/dL would be around 500 at 45, all else equal. That’s still well within the normal range (typically quoted as roughly 300–1,000 ng/dL, though reference ranges vary by lab).

Two things worth understanding about that decline:

Free testosterone declines faster than total. Sex hormone binding globulin (SHBG) rises with age, and SHBG binds testosterone, making it unavailable. So free (usable) testosterone often drops more than the headline number suggests. This is why some men feel symptoms while their total reading looks fine.

A meaningful chunk of the decline is lifestyle, not ageing. Studies comparing older cohorts have found that population-level testosterone has fallen over recent decades independently of age — pointing towards body composition, activity levels and sleep rather than something inevitable about being 45. Men who stay lean, active and well-slept show markedly smaller declines than the average.

That last point is the useful one. A significant portion of what men experience as “age-related testosterone decline” is actually “the accumulated effect of twenty years of poor sleep, rising body fat and no resistance training.”

The Four Things That Actually Matter

Ranked by effect size. Everything else is noise by comparison.

1. Sleep

The largest single modifiable factor, and it’s not close.

The research here is striking: in a well-known study, healthy young men restricted to five hours of sleep a night for one week showed daytime testosterone drop by 10–15%. One week. That’s a decade’s worth of age-related decline, from a bad week of sleep.

Most testosterone release happens during sleep, particularly during deep sleep and REM. Chronically short or fragmented sleep directly cuts production.

What to do: seven-plus hours where possible. Fixed wake time. No alcohol within three hours of bed — it’s a sedative that specifically destroys the deep sleep stages where the hormonal work happens. Sleeping better as a dad covers the practical fixes.

If you’re in a genuinely sleep-deprived season with a newborn, this isn’t a moral failing and there’s no supplement that compensates. Reduce training volume, prioritise protein, and wait it out.

2. Body Fat

Adipose tissue contains aromatase, an enzyme that converts testosterone into oestrogen. More body fat means more conversion, means less testosterone. Lower testosterone then makes it easier to store fat — a genuine feedback loop.

The effect is substantial at higher body fat levels. Men who lose significant weight often see meaningful improvements in testosterone without doing anything else, and interventions producing weight loss reliably show hormonal improvement.

What to do: get to roughly 15% body fat and stay there. Not shredded — that’s counterproductive, since very low body fat and aggressive dieting lower testosterone. There’s a sweet spot, and it’s “lean and healthy,” not “contest ready.” How to lose belly fat after 40 covers getting there.

3. Resistance Training

Heavy compound lifting produces an acute post-exercise testosterone rise. That acute spike is fairly small and its direct contribution to muscle growth is debated — but the long-term picture is clearer: men who lift regularly maintain higher testosterone than men who don’t, largely through improved body composition, insulin sensitivity and sleep quality.

What to do: squats, deadlifts, presses and rows. Three to four sessions a week. Progressive loading. Strength training for men over 40 has the structure.

What not to do: excessive endurance training. Very high-volume endurance work — think marathon-level mileage — is reliably associated with suppressed testosterone. Moderate cardio is fine and good. Running twelve hours a week while under-eating is not.

4. Alcohol

Heavy drinking suppresses testosterone through several mechanisms: direct effects on the testes, elevated cortisol, disrupted sleep, and increased body fat.

The dose matters enormously. Moderate drinking has a small effect. Regular heavy sessions have a large one.

What to do: this is usually the single biggest easy win for dads in their forties. Going from four or five drinking nights a week to one changes sleep, body fat and hormones simultaneously. Cutting back on beer without feeling miserable covers doing it without becoming tedious about it.

What Doesn’t Work

“Testosterone booster” supplements. Tribulus terrestris, fenugreek, ashwagandha, D-aspartic acid, maca, and the rest. The evidence for meaningful testosterone elevation in men with normal levels is weak to absent. Ashwagandha has some reasonable evidence for stress and sleep, which may help indirectly — but that’s a cortisol effect, not a testosterone one.

Zinc and magnesium, unless you’re deficient. If you’re deficient, correcting it helps. If you’re not, supplementing does nothing. Most men eating a reasonable diet aren’t deficient.

Vitamin D, unless you’re deficient. Same logic — though in the UK, winter deficiency is genuinely common, so a modest supplement from October to March is reasonable on general health grounds.

Cold exposure, red light on your testicles, and the various things men on the internet are enthusiastic about. No meaningful evidence.

The uncomfortable summary: nothing you can buy in a tub moves testosterone the way an extra hour of sleep does.

When to Actually See a GP

Get a blood test if you have several of these persistently:

Genuine fatigue not explained by sleep
Low libido or erectile difficulties
Loss of muscle mass despite training
Depressed mood, irritability, poor concentration
Reduced body hair
Hot flushes

Get it done properly: morning test (levels peak early and fall through the day), fasted, and repeated on a second occasion — a single reading is unreliable because levels fluctuate substantially day to day. Ask for total testosterone, free testosterone, SHBG and LH.

Go through your GP, not a private clinic that sells TRT. The incentive problem is obvious. TRT is a legitimate and effective treatment for genuine hypogonadism, and it’s also being sold aggressively to men whose actual problem is sleeping five hours and drinking four nights a week. It’s a lifelong commitment that shuts down your natural production and affects fertility — worth being certain first.

If your levels are genuinely low and your lifestyle is already sorted, TRT is a reasonable conversation to have with a doctor. If your levels are low-normal and you’re sleeping five hours, fix that first and retest in three months.

The Realistic Plan

For a man in his forties who wants to optimise this without buying anything:

Action	Effect
Sleep 7+ hours consistently	Large
Get to ~15% body fat	Large
Lift 3–4× weekly, compound lifts	Moderate
Reduce alcohol to 1 night/week	Moderate
Eat enough — don’t crash diet	Moderate
Adequate dietary fat (0.8g/kg+)	Small but real
Manage stress	Small but real
Vitamin D in winter (UK)	Small, if deficient
Test boosters	None

Notice that every item on that list is something you’d do anyway to look better, feel better and live longer. That’s the honest conclusion here: there’s no separate testosterone protocol. The things that raise testosterone are the same things that get rid of the dad bod, and they work in both directions at once.

Frequently Asked Questions

Does testosterone really drop after 40? Yes, about 1% a year on average. But a substantial part of the typical decline is driven by lifestyle — body fat, sleep, alcohol, inactivity — rather than age itself. Men who stay lean and train show much smaller declines.

Do testosterone boosters work? For men with normal levels, essentially no. The evidence is weak for the popular ingredients. Sleep, body fat and alcohol have far larger effects and cost nothing.

How do I know if my testosterone is low? Symptoms alone aren’t reliable — they overlap heavily with poor sleep, stress, depression and thyroid issues. Get a morning blood test through your GP, repeated on two occasions.

Does lifting weights increase testosterone? It produces a short-term acute rise, and more importantly it improves body composition and sleep, both of which support healthier long-term levels. It’s not a dramatic hormonal intervention — it’s a foundational one.

Should I go on TRT? That’s a conversation for a doctor who isn’t selling it to you, after two confirmed low readings and after you’ve addressed sleep, alcohol and body fat. It’s effective for genuine deficiency and it’s a lifelong commitment with fertility implications.

Does masturbation or abstinence affect testosterone? Essentially no, despite what a certain corner of the internet insists. The transient changes documented are small and short-lived.

Can I raise testosterone naturally at 45? You can restore what lifestyle has cost you, which for many men is a meaningful amount. You can’t get back to your 25-year-old levels. Sleep, leanness, lifting and less alcohol is the whole protocol.

The frustrating and freeing thing about testosterone is that the answer is the same as the answer to almost every other question on this site: sleep more, drink less, lift heavy things, don’t carry more fat than you need to.

There’s no shortcut being withheld from you. There’s just a list of unglamorous things that work, and a large industry hoping you’ll buy something instead.