Researchers looked at data from over 2,000 American men to see if spending time outdoors affects testosterone levels. They found that men who spent more time outside had higher testosterone levels and were less likely to have low testosterone. This connection stayed true even after accounting for other factors like exercise, weight, and diet. The study suggests that our modern indoor lifestyle might be affecting male hormone levels, and getting outside more could be a simple way to support healthy testosterone.

The Quick Take

  • What they studied: Whether the amount of time men spend outdoors is connected to their testosterone levels
  • Who participated: 2,205 adult men from across the United States, average age 45.8 years, with a wide range of health conditions and lifestyles
  • Key finding: For every extra hour spent outside daily, testosterone levels increased by about 9.25 ng/dL, and men were 14% less likely to have low testosterone. About 1 in 5 men in the study had low testosterone levels.
  • What it means for you: Spending more time outdoors may help maintain healthy testosterone levels, but this study shows a connection, not proof of cause-and-effect. More research is needed before making major lifestyle changes based on this finding alone.

The Research Details

This was a cross-sectional study, which means researchers took a snapshot of health information from a large group of men at one point in time. They used data from the National Health and Nutrition Examination Survey (NHANES), a well-respected government health database that tracks Americans’ health and habits from 2011-2014. Researchers measured how much time each man spent outdoors on average per day and compared it to their testosterone levels measured from blood tests. They also collected information about exercise, weight, diet, vitamin D levels, and medical conditions like diabetes to make sure outdoor time was the real factor affecting testosterone, not these other things.

This research approach is important because it looks at real-world data from thousands of people rather than just a small group in a lab. By measuring actual outdoor time and actual testosterone levels, researchers can spot patterns that might explain why modern indoor lifestyles could affect male hormones. The study controlled for many other factors that affect testosterone, which helps show that outdoor time itself might be important.

This study has good strengths: it included over 2,000 men from different backgrounds, used actual blood tests for testosterone (not estimates), and adjusted for many other factors that could affect results. However, because it’s a snapshot study, it can only show that outdoor time and testosterone are connected—not that one causes the other. The study also relied on men reporting their own outdoor time, which might not be perfectly accurate. Published in a respected medical journal, this research provides solid evidence worth paying attention to, but it’s not the final word on the topic.

What the Results Show

Men in the study spent an average of 144 minutes (about 2.4 hours) outdoors per day. The average testosterone level was 448.34 ng/dL, and about 19% of men had low testosterone (below 300 ng/dL). The main finding was clear: for every additional hour spent outside daily, testosterone levels increased by about 9.25 ng/dL. This might sound small, but it adds up—spending 3 extra hours outside instead of 2 could mean a 9-point increase in testosterone. Men who spent more time outdoors were also 14% less likely to have low testosterone overall. This connection remained strong even after researchers accounted for age, weight, exercise levels, diet, vitamin D, and other health factors.

The study also confirmed what scientists already knew: older men tend to have lower testosterone, heavier men are more likely to have low testosterone, and men with diabetes are at higher risk for low testosterone. Interestingly, men who exercised more had higher testosterone levels, which supports the importance of physical activity. The outdoor time finding was independent of these factors, meaning it appeared to be its own separate influence on testosterone.

This is the first study to specifically look at the connection between outdoor time and testosterone levels while controlling for so many other factors. Previous research has shown that sunlight exposure affects vitamin D production and that vitamin D relates to testosterone, but this study found the outdoor time effect even after accounting for vitamin D levels. This suggests that something about being outside—possibly sunlight, fresh air, or other environmental factors—may directly influence testosterone beyond just vitamin D production.

This study shows a connection but cannot prove that outdoor time causes higher testosterone. Men reported their own outdoor time, which might not be completely accurate. The study was done in 2011-2014, so patterns might have changed since then. The research only included men, so we don’t know if these findings apply to women. Additionally, the study couldn’t explain exactly why outdoor time matters—whether it’s the sunlight, physical activity done outside, or something else entirely.

The Bottom Line

Based on this research, spending more time outdoors appears to be associated with healthier testosterone levels. A reasonable goal might be to gradually increase outdoor time to 2-3 hours daily if possible. This recommendation has moderate confidence because the study shows a clear connection but cannot prove cause-and-effect. Combine outdoor time with regular exercise and healthy eating for best results. If you have concerns about low testosterone, talk to your doctor about testing and personalized recommendations.

This research is most relevant to adult men concerned about testosterone levels or general health. Men with low testosterone symptoms (fatigue, low mood, reduced muscle mass) should especially consider this finding. Men over 40 may find this particularly useful since testosterone naturally declines with age. However, this research shouldn’t replace medical advice—if you suspect low testosterone, get tested by a doctor. Women shouldn’t assume these findings apply to them without more research.

Changes in testosterone from increased outdoor time would likely take weeks to months to become noticeable. You probably won’t feel different after one day outside, but consistent outdoor time over 4-8 weeks might contribute to improvements in energy, mood, or muscle maintenance. Individual results vary based on age, health status, and other factors.

Want to Apply This Research?

  • Track daily outdoor time in minutes and record weekly average. Aim to gradually increase from current baseline to 120-180 minutes daily. Log this alongside energy levels and mood to notice personal patterns.
  • Set a daily outdoor time goal (start with 30 minutes if currently sedentary, work up to 2+ hours). Schedule outdoor activities like walking, gardening, or outdoor exercise. Use app reminders to take outdoor breaks during work. Track which outdoor activities you enjoy most to build sustainable habits.
  • Monitor outdoor time weekly and monthly trends. Note correlations with energy, sleep quality, and mood. If possible, get testosterone tested annually through your doctor to see if increased outdoor time correlates with your personal levels. Track seasonal changes since outdoor time naturally varies by season.

This research shows a connection between outdoor time and testosterone levels but does not prove that outdoor time causes higher testosterone. Individual results vary based on age, genetics, health conditions, and other factors. This information is for educational purposes only and should not replace professional medical advice. If you have concerns about low testosterone, fatigue, or other health issues, consult with a healthcare provider for proper testing and personalized treatment recommendations. Always talk to your doctor before making significant lifestyle changes, especially if you have existing health conditions or take medications.