Why Testosterone Is Declining in Young Men, and What Strength and Performance Coaches Can Do About It
Every strength and performance coach should be aware of this testosterone trend in young men and understand how to leverage their programming strategy to help.
Written by Hannah Witt
If you coach adolescent or young adult male clients, there’s a hormonal trend happening that deserves your attention, and it’s one that likely won’t show up in a client intake form. Instead, it shows up in their energy, motivation, recovery and body composition.
Total testosterone levels in young men have been quietly declining over the past couple of decades, independent of the well-known age-related drop that occurs later in life. As a strength and conditioning professional, understanding why this is happening, and how your programming choices can help, puts you in a position to genuinely improve your clients’ long-term health, not just their squat numbers.
Why Testosterone Health Matters
Testosterone isn’t just a male hormone tied to libido and muscle. It’s a systemic regulator of health. It supports muscle protein synthesis and lean mass maintenance, contributes to bone density, helps regulate insulin sensitivity and body fat distribution, and plays a role in mood, cognitive function and motivation (Ide, 2023).
Low testosterone in men is linked to a higher risk of conditions like metabolic syndrome, cardiovascular disease and osteoporosis, and it can meaningfully erode quality of life well before those diagnoses ever appear on paper (Ide, 2023).
Historically, testosterone decline has been framed as an older man’s problem: a natural consequence of aging as testicular function slows and sex hormone-binding globulin (SHBG) rises, reducing the amount of free, biologically active testosterone in circulation (Ide, 2023; Cohen et al., 2020).
That framing is still true. But it’s incomplete.
Testosterone Decline Isn’t Just an Aging Story Anymore
A widely cited analysis of National Health and Nutrition Examination Survey (NHANES) data tracked total testosterone in men aged 15 to 39, from 1999 through 2016 (Lokeshwar et al., 2020). The findings are striking. Average testosterone levels dropped substantially over that period, even after adjusting for age, activity level, smoking, alcohol use and comorbidities (Lokeshwar et al., 2020). Rising body mass index tracked alongside the decline and was independently associated with lower testosterone.
But here’s the part that should catch a coach’s attention: Even young men with a normal BMI showed significantly lower testosterone at the end of the study period compared to the beginning (Lokeshwar et al., 2020).
In other words, obesity and metabolic health explain part of the story, but not all of it. Something broader appears to be shifting testosterone levels downward in young men.
Researchers point to a mix of possible contributors: changes in dietary composition, increased exposure to certain environmental compounds and lifestyle factors such as reduced physical activity (Lokeshwar et al., 2020).
Complicating the picture further, adolescent and young men often don’t present with the “classic” low-T symptoms coaches might expect from an older client, such as reduced libido or erectile dysfunction. Instead, the most reliable early flag in this age group tends to be something far more mundane: persistent low energy and lack of motivation (Cohen et al., 2020).
That’s a symptom easy to write off as just being a teenager or burned out from school, But it’s worth paying attention to, especially alongside other markers. These include reduced strength gains, unexplained loss of muscle mass, increased body fat accumulation, delayed or reduced facial/body hair development or lingering fatigue that doesn’t respond to better sleep (Cohen et al., 2020).
Known modifiable risk factors for low testosterone in young men include obesity, poorly managed diabetes, chronic opioid or certain analgesic use, anabolic steroid use, and heavy environmental toxin exposure such as to tobacco smoke and certain pesticides (Cohen et al., 2020).
As a coach, you’re not diagnosing hypogonadism — that’s a medical determination requiring blood work — but you are often the first person to notice a pattern of symptoms worth referring out for evaluation.
What Role Does Nutrition Play?
Diet composition has a real, measurable effect on testosterone. One area worth understanding is the interaction between carbohydrate intake, protein intake and hormone response. This is something coaches recommending nutrition strategies to clients on low-carbohydrate or ketogenic protocols should know.
A systematic review and meta-analysis of low-carbohydrate diets found that the effect on testosterone depends heavily on protein intake, not just carbohydrate restriction (Whittaker & Harris, 2022). Moderate-protein, low-carbohydrate diets showed no consistent effect on resting total testosterone. However, high-protein, low-carbohydrate diets (roughly 35% or more of total energy from protein) were associated with a large decrease in resting total testosterone, enough to represent a meaningful percentage drop relative to typical levels in young men (Whittaker & Harris, 2022).
The proposed mechanism involves the urea cycle. Very high protein intake may exceed the body’s capacity to process the resulting nitrogen load efficiently, and testosterone appears to be part of the hormonal response that shifts to accommodate that burden (Whittaker & Harris, 2022).
The same research found that short-term low-carbohydrate diets (under roughly three weeks) tend to raise resting cortisol, though this effect largely normalizes after the body adapts (Whittaker & Harris, 2022). Post-exercise cortisol, however, remained elevated on low-carbohydrate diets even after the adaptation period, particularly following longer-duration training sessions (Whittaker & Harris, 2022).
Since cortisol and testosterone have an inverse, competing relationship in the body, chronically elevated cortisol from carbohydrate restriction around demanding training sessions is a variable worth managing for clients pursuing both a low-carb approach and serious strength or hypertrophy goals.
The practical takeaway for coaches? Moderate protein intake is generally not a concern for testosterone, and most people following realistic diets naturally stay in that moderate range. But if a client is deliberately pushing protein very high while cutting carbohydrates aggressively (a combination increasingly promoted online), it’s worth flagging that this specific combination is the one associated with the largest negative hormonal effect, and suggesting a more moderate protein target instead.
Beyond low-carb-specific research, body composition itself is one of the most consistent nutrition-adjacent levers for testosterone. Obesity suppresses testosterone through multiple pathways, including lower SHBG and increased peripheral conversion of testosterone to estrogen in adipose tissue (Ide, 2023; Cohen et al., 2020), while even modest, sustainable weight loss in men carrying excess body fat has been shown to raise testosterone levels (Ide, 2023; Cohen et al., 2020).
For coaches working with young clients carrying excess adiposity, sound, sustainable fat loss programming is itself a testosterone intervention.
Why Resistance Training Belongs at the Center of Your Programming
If there’s one lever coaches have the most direct control over, it’s training design, and the evidence here is genuinely encouraging.
Resistance training reliably produces an acute rise in testosterone following a session, and research has identified several variables that predict how strong that response will be (Turgut et al., 2021):
• Training large muscle groups produces a bigger acute testosterone response than training isolated small muscle groups alone (Turgut et al., 2021).
• Hypertrophy-style protocols: Moderate-to-high volume (around 8-10+ sets, ~10 reps), moderate loads (roughly 70-75% one rep max) and shorter rest periods (60-120 seconds) consistently produce a larger testosterone response than pure maximal-strength or power-focused protocols using low reps and long rest (Turgut et al., 2021).
• Free weights and compound, functional movements (squats, presses, strongman-style implements) tend to elicit a greater hormonal response than machine-based, single-joint exercises (Turgut et al., 2021).
• Exercise order matters: Sequencing large-muscle-group exercises before small-muscle-group exercises produces a greater testosterone increase than the reverse order (Turgut et al., 2021).
• Shorter rest intervals between sets (60-90 seconds vs. 120+ seconds) tend to produce a somewhat larger acute hormonal response, within reason (Turgut et al., 2021).
• Sufficient training volume and intensity are non-negotiable. Under-dosed sessions don’t reliably move the needle (Turgut et al., 2021).
The picture for chronic, long-term testosterone adaptations from consistent resistance training is more mixed across the research base. Some studies show sustained increases in resting testosterone after months of training, while others show no measurable change, particularly in older or already well-trained populations (Turgut et al., 2021).
This doesn’t mean resistance training doesn’t work for long-term hormonal health. It likely means the benefit shows up less as a permanent spike in resting testosterone and more through the repeated acute responses, the muscle mass and improved insulin sensitivity training builds over time, and reductions in body fat. All of which independently support healthier long-term testosterone status.
Practical Programming Takeaways for Coaches
For a young male client where healthy testosterone status is a goal, whether explicitly stated or simply a byproduct of good general programming, consider:
1. Anchoring programming around compound, multi-joint, free-weight movements (squats, deadlifts, presses, rows) rather than building a program primarily around machines and isolation work.
2. Including a genuine hypertrophy training block, not just strength or power work. This should include moderate loads, higher volume and shorter rest periods, at least part of the training year.
3. Sequencing big-muscle-group compound lifts early in the session, saving smaller, isolation-focused accessory work for later.
4. Supporting fat loss when relevant through sustainable nutrition strategies rather than extreme approaches, since excess adiposity is one of the more robust predictors of low testosterone in this age group.
5. Being cautious about recommending very high-protein, low-carbohydrate combinations for clients whose goals depend on healthy hormonal status. Favor moderate protein targets over extreme ones.
6. Watching for the quieter warning signs in young clients: persistent low energy, unexplained plateaus or regression in strength, and disproportionate fatigue. Know when a referral to a physician for bloodwork is the right next step rather than trying to program your way around a potential medical issue.
Testosterone health isn’t just a topic for aging male clients anymore. The data suggests a generational shift is underway. Coaches who understand the modifiable pieces — training structure, body composition and nutrition strategy — are well-positioned to help young clients build not just strength but also a healthier long-term hormonal foundation.
Up Next: Read what strength and performance coaches should know about GLP-1s.
This article is intended for educational purposes for fitness and strength and conditioning professionals and is not a substitute for individualized medical advice. Any client showing persistent symptoms suggestive of hormonal imbalance should be referred to a qualified physician for proper evaluation and bloodwork.
References
Cohen, J., Nassau, D. E., Patel, P., & Ramasamy, R. (2020). Low testosterone in adolescents & young adults. Frontiers in Endocrinology, 10, 916. https://doi.org/10.3389/fendo.2019.00916
Ide, H. (2023). The impact of testosterone in men’s health. Endocrine Journal, 70(7), 656–662.
Lokeshwar, S. D., Patel, P., Fantus, R. J., Halpern, J., Chang, C., Kargi, A. Y., & Ramasamy, R. (2020). Decline in serum testosterone levels among adolescent and young adult men in the USA. European Urology Focus. https://doi.org/10.1016/j.euf.2020.02.006
Turgut, A., Varol, S., Yazıcı, A., & Günay, M. (2021). The effect of resistance exercises on testosterone. The Journal of Eurasia Sport Sciences and Medicine, 3(1), 1–9.
Whittaker, J., & Harris, M. (2022). Low-carbohydrate diets and men’s cortisol and testosterone: Systematic review and meta-analysis. Nutrition and Health, 28(4), 543–554. https://doi.org/10.1177/02601060221083079
Hannah Witt is a UESCA Certified Running Coach, endurance athlete, and content creator with a background in Human Biology and competitive collegiate running. Still actively training at a high level with 80+ mile weeks, she is passionate about helping runners pursue long-term performance through thoughtful training, injury prevention, strength work, and sustainable fueling practices. Through her coaching, Instagram platform, and YouTube interview series, The Performance Collective, Hannah aims to create an education-based support network that makes evidence-informed endurance training more approachable, empowering, and community-driven for runners of all levels, while also advocating strongly for animal welfare and rescue.
