I have never looked into testosterone before. After some research, I cannot find anything to support your claim about what's happened since the 60s, but it soun

I have never looked into testosterone before. After some research, I cannot find anything to support your claim about what's happened since the 60s, but it sounds unreasonable to me. Average levels appear to have been dropping since the 80s, but not by such a significant scale as you claim. I did however find this harvard article with the following passage: https://www.health.harvard.edu/mens-health/obesity-unhealthy-and-unmanly https://www.health.harvard.edu/mens-health/obesity-unhealthy... > Obesity lowers testosterone levels. For example, a 2007 study of 1,667 men ages 40 and above found that each one-point increase in BMI was associated with a 2% decrease in testosterone. In addition, a 2008 study of 1,862 men ages 30 and above found that waist circumference was an even stronger predictor of low testosterone levels than BMI. A four-inch increase in waist size increased a man's odds of having a low testosterone level by 75%; for comparison, 10 years of aging increased the odds by only 36%. All in all, waist circumference was the strongest single predictor of developing symptoms of testosterone deficiency.