Plastics and what not feel like easy targets, but I would bet this is primarily BMI. The paper seems to conclude that BMI is the big part.
> Elevated BMI was associated with reduced total testosterone levels (P < .0001), with the mean BMI increasing from 25.83 in 1999-2000, to 27.96 in 2015-2016 (P = 0.0006).
They do say:
> Lokeshwar noted that even men with a normal BMI (18.5-24.9) had declining total testosterone levels (P < .05) during the same time frames.
However the range of 18.5-24.9 is wider than the mean increase that they think is the most noteworthy independent variable. It's fully possible that within the BMI band of 18.5-24.9, average BMI nonetheless increased and is the primary driver. Note that the effect size over time is muuuuch more significant when not controlling for binned BMI.
That doesn't mean whatever environmental shit you're not fond of is safe of course. Heck, in some roundabout way it may even be contributing to obesity, possibly even through other hormonal changes. Wouldn't be my first guess though.
Completely agree about BMI ranges potentially being too wide.
I just checked Fitbit and was surprised to see I’m now in the “ideal” range. I have man boobs and a muffin top. While I’m rarely the fattest person around anymore, I’m very clearly still overweight.
It’s rare enough to see men that aren’t visibly overweight that it feels like a real exception when I do.
I suspect there are _lots_ of fat men with an “ideal” BMI 18.5-24.9.
> I just checked Fitbit and was surprised to see I’m now in the “ideal” range. I have man boobs and a muffin top. While I’m rarely the fattest person around anymore, I’m very clearly still overweight.
In college a classmate used the term "skinny fat" to describe himself, same body type you describe. He was within the healthy weight range for his height and frame, but because of poor diet and exercise (primarily exercise) he had a rather high body fat percentage. It's easy to hit that point if you have a halfway decent diet (at least by calorie count) but a sedentary lifestyle (like us at the time, and perhaps more now, living on our computers playing video games and programming). The rest of us were just "fat fat" since our diets (especially sodas, he never drank any and some of us were only hydrated because of them) were much worse than his and we were similarly sedentary.
Also, the "muffin top" only really goes away at like 15% body fat or lower. I had a small muffin top back in college with an incredibly active lifestyle (lots of walks all the time) and a BMI of 21.8 (well into the 'ideal' range)
Body fat percentage is the more sensitive and specific indicator for health outcomes, though.
I realize not everyone has access to the equipment necessary to get a good BF% measurement (handheld devices and scales are garbage – you need a laboratory). However, measuring circumference around the waist at about the height of the bellybutton accomplishes approximately the same thing. (This will not be your pants size.) Above 37 or 38, things get dicey.
I'm happy to dig up references if you're curious about the details.
At 6'0", 215 lbs, and 10% body fat (via DEXA scans) I have a BMI of 29.2 - on the high end of "overweight" - almost "obese". I'm a fit, but not especially big, casual weightlifter with a desk job.
One other interesting factor: BMI is a rough measure with substantial room for error. Everyone likes to criticize BMI because a lean athlete can show up as "overweight" due to muscle, but the opposite is also true. If you have a lot less muscle then increased fat can show up as "normal".
I would hazard a guess that there are a lot more people with less lean muscle tissue than the 1970s, so BMI can understate how fat people are.
control is a weird term. I don't have the paper to validate, but I'd guess by control they meant they verified the effect was visible within BMI bands based on the wording of the article.
> Elevated BMI was associated with reduced total testosterone levels (P < .0001), with the mean BMI increasing from 25.83 in 1999-2000, to 27.96 in 2015-2016 (P = 0.0006).
They do say: > Lokeshwar noted that even men with a normal BMI (18.5-24.9) had declining total testosterone levels (P < .05) during the same time frames.
However the range of 18.5-24.9 is wider than the mean increase that they think is the most noteworthy independent variable. It's fully possible that within the BMI band of 18.5-24.9, average BMI nonetheless increased and is the primary driver. Note that the effect size over time is muuuuch more significant when not controlling for binned BMI.
That doesn't mean whatever environmental shit you're not fond of is safe of course. Heck, in some roundabout way it may even be contributing to obesity, possibly even through other hormonal changes. Wouldn't be my first guess though.