I agree there is no single isolated cause but multiple factors of declining testosterone levels. Body fat and obesity is also linked to reduced testosterone lev

I agree there is no single isolated cause but multiple factors of declining testosterone levels. Body fat and obesity is also linked to reduced testosterone levels, and lifestyle in western countries (the US in particular) leads to more and more overweight and obese population. So if you are concerned about your testosterone levels, and immediate step you can take is to reduce your body fat.