The research behind Teak's 12-week programme

Teak is a coaching service, not a medical one, and we don't publish client stories, star ratings, before-and-after photos or results figures. Every man starts from a different place, and no coach can promise what your next blood test will say. What we can show you is the published research behind each part of the 12-week programme: who was studied, how many, what changed, and what each study can't tell you.

Why does Teak show research instead of testimonials?

Because you can check it. In February 2026 the University of Sydney reported on a study of 46 high-reach Instagram and TikTok posts promoting testosterone tests and treatments. None cited any scientific evidence, 72% had a financial interest behind them and 67% included a direct purchase link.¹ We'd rather show our working. Each study below is described as a finding in a particular group of men, never as a result you should expect. How we choose and describe sources is set out in our editorial policy.

What does the research say, habit by habit?

Habit	What studies found	Source
Sleep	10 healthy men averaging 24: after eight nights of 5 hours in bed, daytime testosterone was 10-15% lower than after 10-hour nights	Leproult 20112
Body fat	Review of 24 studies: testosterone rose after weight loss, more in men who lost more. Sydney study of 17 men with obesity: about 0.6% higher total testosterone for each kilo lost over three years	Corona 20133; Brzozowska 20244
Alcohol	10 middle-aged men: three weeks of 40 g of alcohol a day in beer left testosterone 6.8% lower than three weeks of alcohol-free beer	Sierksma 20045
Training	Two 12-week studies without a control group (41 overweight men; 22 inactive men aged about 62) found rises. A pooled analysis of 11 randomised trials in 421 inactive, healthy men found no average change in resting testosterone	Kumagai 20166; Hayes 20177; Potter 20218
Stress	50 soldiers on an 8-week course with a daily energy shortfall of about 1,000 kcal: testosterone fell and cortisol rose. 65 men living with HIV: free testosterone rose after a 10-week stress-management course and fell in a wait-list group	Nindl 20079; Cruess 200021
Pelvic floor	55 men with erection problems, seen at a UK hospital: by six months after pelvic floor exercises with biofeedback, 40% had normal erectile function, 34.5% had improved and 25.5% had not	Dorey 200410

The sections below give the detail and, just as important, the limits.

Does poor sleep lower testosterone?

In one small laboratory study it did, modestly. Ten healthy men with an average age of 24 spent three nights with 10 hours in bed, then eight nights with 5 hours. Daytime testosterone averaged 16.5 nmol/L (about 476 ng/dL) after the short nights, against 18.4 nmol/L (about 531 ng/dL) after the long ones.² You can check those conversions with our unit converter.

The limits matter. The authors call it a small convenience sample: 10 young men in a lab, compared against unusually long nights.² A review from the University of Adelaide found the evidence that short sleep lowers testosterone directly, rather than through other health problems, is unclear and on balance weak. It also found that sleep apnoea seems to have no direct effect once age and obesity are allowed for, and that in most studies, treating moderate to severe sleep apnoea with a CPAP machine didn't reliably raise testosterone.¹¹ The Sleep Health Foundation says most adults need 7 to 9 hours a night,¹² and we coach toward that. Loud snoring, pauses in breathing or heavy daytime sleepiness can be signs of sleep apnoea, so those go to a GP.¹³

Does losing weight raise testosterone?

In men carrying extra weight, studies consistently find testosterone rises as the weight comes off, and this is the strongest evidence on the page. A review of 24 studies found testosterone rose after both low-calorie diets and weight-loss surgery, with bigger rises in men who lost more weight and in younger men without diabetes who started heavier.³ The Adelaide review describes the rise as predictable and in proportion to the weight lost.¹¹ At the Garvan Institute in Sydney, researchers followed adults with obesity for three years and found each kilo lost was linked with about 0.6% higher total testosterone in the men.⁴

Limits: the Sydney study included only 17 men, 13 of whom had weight-loss surgery, and nobody was randomised.⁴ In the review, surgery produced bigger rises than dieting.³ Healthy Male notes the effect is largest in people with more weight to lose.¹⁴ These studies say little about men who are already lean. Our approach is in how to increase testosterone naturally.

Does alcohol lower testosterone?

In one controlled trial, about four standard drinks a day lowered it a little. In the Netherlands, 10 healthy middle-aged men drank beer with dinner for three weeks, giving 40 g of alcohol a day, and alcohol-free beer for another three weeks, in random order. All their food was supplied and kept the same. Testosterone was 6.8% lower after the beer weeks.⁵

A standard drink holds about 10 g of alcohol in both countries,^15,16 so 40 g is about four standard drinks a day, or 28 a week. Australia's guidelines are no more than 10 standard drinks a week and no more than 4 on any one day.¹⁵ Health New Zealand's advice for men is no more than 15 a week and 3 a day, no more than 5 at one time, and at least two alcohol-free days a week.¹⁶

Limits: 10 men, three weeks, one type of drink, and the result was only just clear of chance (the likely drop ranged from about 1% to 12.5%).⁵ If cutting back feels hard, that's a GP conversation, and we'll say so.

Does exercise increase testosterone?

Not reliably, on the best evidence so far. Two studies without a control group found rises. In Japan, 41 overweight and obese men averaging 49 years did a 12-week programme of walking or jogging classes plus a reduced-calorie diet. They lost about 12 kg on average, testosterone rose, and it rose more in the men who increased their daily steps the most.⁶ In Scotland, 22 inactive men averaging 62 did six weeks of conditioning, then six weeks of high-intensity intervals on an exercise bike. Total testosterone ended about 17% higher, with most of that rise (about 10%) in the first six weeks, but free testosterone rose only about 4.5%.⁷

Both sets of authors name the missing control group as a limit, so those rises can't be pinned on the training itself.^6,7 When researchers pooled 11 randomised trials that did have a control group, covering 421 inactive but healthy men aged 19 to 75 doing aerobic, weights or combined training for a median of 12 weeks, training made no difference on average to resting testosterone.⁸ A hard weights session can lift testosterone for 15 to 30 minutes afterwards, but many studies find no change in resting levels even as strength improves.¹⁷

So we plan training for strength, fitness and body fat, not as a testosterone lever on its own. Targets follow Australia's advice of at least 30 minutes of moderate activity on most days¹⁸ and New Zealand's of at least 2.5 hours a week,¹⁹ with muscle strengthening on at least two days a week in both.^18,19

Does stress lower testosterone?

It may, but the direct evidence for everyday stress is thin. In 50 male soldiers on an eight-week US Army Ranger course, with an average energy shortfall of about 1,000 kcal a day, total testosterone fell and cortisol rose.⁹ The men also lost about 13% of their body weight, so it's hard to separate stress from hard physical work and too little food, and the result says little about a busy job. Healthy Male explains that cortisol released over long periods can reduce testosterone production and dampen sex drive.²⁰

The closest trial we found was in 65 men living with HIV who had symptoms. Free testosterone rose in the 42 who did a 10-week group stress-management course and fell in the 23 on a wait-list.²¹ That's a very specific group. We haven't found a trial showing that stress management on its own raises resting testosterone in otherwise healthy men, and we won't pretend otherwise. Stress is in the plan because it often shows up in the other habits: late nights, extra drinks, skipped sessions. If stress has turned into low mood or anxiety that won't lift, that's for a GP. Our safety page explains when we refer.

Can pelvic floor exercises help erections?

In trials of men with erection problems, pelvic floor training helped many but not all. In a UK randomised trial, 55 men with erection problems (median age 59, range 22 to 78) were recruited from a local urology clinic and seen at a hospital in Somerset. Of these, 28 did pelvic floor exercises with biofeedback plus lifestyle advice, and 27 got lifestyle advice alone. At three months the exercise group had better erectile function scores. The advice-only group then switched to the exercises and improved too. Across all 55 men, 22 (40%) had normal erectile function by the six-month assessment, 19 (34.5%) had improved and 14 (25.5%) had not.¹⁰

A 2019 review from James Cook University in Townsville found 10 trials on erection problems and premature ejaculation. Every trial that measured erectile function showed improvement, but the studies were of low to moderate quality and no best routine was identified.²² Healthify says building pelvic floor strength takes 3 to 6 months of regular training.²³

Keep the setting in mind. The UK men were seen in hospital and used biofeedback equipment,¹⁰ which coaching over WhatsApp doesn't replicate. Teak's pelvic floor programme is general exercise coaching, not a treatment for erection problems.

Two rules we hold to. New or ongoing erection problems go to a GP first, because they can be the first sign of heart disease, diabetes, high blood pressure or high cholesterol.²⁴ And if you're not sure you're doing the exercises right, or you have leaking, a pelvic health physiotherapist or continence nurse can check your technique.^23,25 In Australia the National Continence Helpline is 1800 33 00 66;²⁵ in New Zealand, Continence NZ's helpline is 0800 650 659.²⁶

What doesn't the evidence show?

• What will happen to you. Every figure above describes a group. Men in the same study responded differently; in the pelvic floor trial, about a quarter didn't improve.
• That the men studied are like you. They included young lab volunteers, adults with obesity (most having surgery), overweight men in Japan, inactive older men in Scotland, men from a UK urology clinic, soldiers and men living with HIV.
• Certainty. Most studies were small, short or had no control group. When randomised exercise trials were pooled, the average effect on resting testosterone was nil.
• A fix for medical causes. Some causes of low testosterone need a doctor, not a coach. See who Teak isn't for.
• Anything about medication. Whether testosterone treatment suits anyone is a doctor's decision. We explain the difference in coaching vs TRT.

This page is general information, not medical advice. To see how a coach turns it into a plan, read how it works. Spot an error or a study we've missed? Email hello@jointeak.com and we'll check it.