Does exercise increase testosterone?
Broadly, yes — but the size and direction of the effect depend on who you are, what you do, and how much fat you are carrying. Testosterone is the primary male sex hormone, and it also matters for muscle, bone, mood and metabolic health in everyone. Levels tend to drift downward from around the age of 30, and being overweight accelerates that decline. Exercise is one of the few levers you genuinely control, so it deserves your attention — but the honest picture is more nuanced than “train hard, get more testosterone.”
According to PubMed, a systematic review of 33 studies in adults over 40 found that exercise training raised basal levels of testosterone, along with growth hormone, IGF-1, SHBG and DHEA, in both men and women. Notably, the increases occurred largely independent of the mode, duration or intensity of the programme (Zouhal et al., 2021, linked at 10.1007/s40279-021-01612-9). In other words, training consistently nudges the hormonal environment in a favourable direction as you age — the type of training seems to matter less than the fact that you are doing it at all.
How much of the effect is really about losing fat?
For many men, the largest and most reliable testosterone gains from exercise come indirectly — through losing excess body fat. Fat tissue contains the enzyme aromatase, which converts testosterone into oestrogen, so carrying more fat tends to mean lower testosterone. A 2024 review of weight loss and testosterone concluded that reducing body mass index reliably raises serum testosterone, and that the effect is mediated by lower aromatase activity, improved insulin sensitivity and reduced inflammation (Okobi et al., 2024, at 10.7759/cureus.76139).
A separate narrative review of weight-loss strategies reached the same conclusion for lifestyle change specifically: diet and regular exercise improved both testosterone levels and sexual function in men with obesity, with several randomised controlled trials supporting the finding (Santamaria et al., 2024, at 10.1177/17562872241279648). If you are carrying extra weight, this is the most important point on the page: the fastest route to healthier testosterone is often simply getting leaner, and exercise that burns fat does double duty.
Does the type of training matter — weights, or intervals?
Resistance training has the strongest reputation here, and the evidence broadly supports it. A 12-week randomised controlled trial in sedentary, obese men with type 2 diabetes compared resistance training with aerobic training. Both improved health markers, but resistance training produced the greater effect on testosterone (effect size 0.52) and on muscle strength, while aerobic training did more for the lipid profile (Duan & Lu, 2024, at 10.52082/jssm.2024.495).
High-intensity intervals hold their own too. A 2024 meta-analysis in older adults compared high-intensity interval training (HIIT) with continuous moderate-intensity training. For most outcomes the two were similar, but HIIT — and not the steadier moderate work — produced a significant increase in testosterone (effect size 0.34), alongside greater reductions in fat mass and waist circumference (Oliveira et al., 2024, at 10.1016/j.archger.2024.105451). The common thread across resistance work and intervals is intensity: brief, genuinely hard efforts appear to signal the body more effectively than long, comfortable sessions.
This is where REHIT — Reduced Exertion High-Intensity Interval Training, CAROL’s signature protocol of two 20-second all-out sprints inside a roughly five-minute session — fits the pattern. REHIT is built around exactly the sort of maximal, short-duration effort that the interval research points to, and it doubles as an efficient way to shed the fat that suppresses testosterone in the first place. The evidence above is on HIIT and resistance training rather than REHIT specifically, so we would not overclaim a direct hormonal result; but the mechanism it trains — hard, brief intensity — is the one that keeps showing up.
Can you overdo it?
Yes, and this is the part that rarely makes the headlines. Very high training volumes, particularly sustained endurance work without enough fuel, can push testosterone the other way. Chronic low energy availability — not eating enough to cover the demands of heavy training — is associated with reduced testosterone, lower bone density and a depressed resting metabolic rate in male endurance athletes (Cupka & Sedliak, 2023, at 10.4081/ejtm.2023.11104). The mechanism appears to sit in the hypothalamic-pituitary-gonadal axis, the body’s hormonal control system, responding to a persistent energy shortfall.
For the average person training a few times a week and eating enough, this is not a concern. It becomes relevant only at the extreme end — high-mileage runners and cyclists under-fuelling for months. The practical lesson is that more is not always better: the goal is a hard, sufficient stimulus followed by adequate recovery and nutrition, not an endless grind.
What about women?
The testosterone conversation is usually framed around men, but women produce and rely on testosterone too, in smaller amounts. Here the picture can invert. In women with polycystic ovary syndrome — a condition marked by elevated androgens — 12 weeks of high-intensity interval training significantly lowered serum testosterone and body fat compared with strength training (Rao et al., 2022, at 10.5468/ogs.22002). That is a desirable outcome in that context. It is a useful reminder that exercise regulates hormones toward a healthier balance rather than simply pushing a single number up.
The bottom line
Does exercise increase testosterone? For most men, yes — modestly and reliably — and the effect is largest when training helps you lose excess fat. Resistance training and hard intervals appear to do more than long, easy cardio, and consistency matters more than any single method. The exceptions are worth remembering: chronic under-fuelled endurance training can lower testosterone, and in some contexts — such as PCOS — lowering it is exactly the point. As ever, we would rather anchor expectations to the evidence than promise a number. The broader prize is the one that matters most for how long and how well you live: intense, efficient exercise builds cardiorespiratory fitness and a healthier body composition, and healthier testosterone tends to come along for the ride.
