I would wager that there are a multitude of factors involved in this. First, humans are materially wealthier than ever before, and as such “the plague of parad

I would wager that there are a multitude of factors involved in this. First, humans are materially wealthier than ever before, and as such “the plague of paradise” becomes an issue. Without struggle, humans go soft. Look at the Mongolian conquerors as the most striking example of this. For all of us today, we don’t struggle in a physical manner to the same extent those before us did. Second, all incentives in our daily lives push us toward peaceful, sedentary, and “soft” behavior. This reinforces the first. Third, obesity is a problem. As noted in the OP, as obesity increases testosterone levels decrease. Given how much of the population is overweight, I’m not surprised by the lowering of testosterone. Fourth, exercise. Many here have noted that earlier generations were far more active. Every doctor with whom I’ve ever spoken has stated that diet and exercise are required for health, and in my experience every part of my life improved by losing 50 lbs and getting moving every day. Finally… levothyroxine is the second most commonly prescribed medicine in the USA. The thyroid is highly sensitive to radioactivity, heavy metals, PCAs, PBA, PFOAs, pesticides, and herbicides. These can all damage the thyroid or prevent the function of the thyroid and/or thyroid hormones. Thyroid mal/dysfunction has a vast array of effects on the body and can lead to a decrease in the function of many other parts of the body. While I don’t know if it will affect testosterone production, it wouldn’t surprise me at all. These pollutants can also cause autoimmune disorders which can damage the body (including the thyroid). If we already know that hormone production can be impaired by pollution, I don’t find it far fetched to think that this would include testosterone.