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Everyone loves to flaunt this theory, as well as the sperm quality one. I think both are wrong, or at least, minor effect sizes relative to the bigger picture.

Everyone loves to flaunt this theory, as well as the sperm quality one. I think both are wrong, or at least, minor effect sizes relative to the bigger picture. The sperm quality drop is due to obesity plain and simple. It's a well studied, strong effect size. The rise of obesity itself has many obvious causes. Sedentary work, high calorie, high sugar/sweetener diets. If it were microplastics you would expect to see this as a universal effect, but it's really not. While obesity is rising on average, it's highly concentrated. Many communities, especially affluent ones, have very low obesity rates still. Very few people in my social / work circle are obese. And like, although I've cut out soda and most of the obvious bad things, its still apparent to me that my diet is likely overloaded with sugar and sweeteners much more than past generations. Poor people have high stress, insufficient money to buy quality food, and insufficient time / hardware to invest in food preparations on a regular basis. And we have case examples too. Remote Amazonian (brazil) populations get introduced to nestle food? Wait several years and bam, fat. Why are pets getting fatter? Because they're eating garbage too. Why are wild animals getting fatter? Because they're eating garbage too. You then see follow up questions like "Why are sperm quality readings dropping in dogs?" It's because they're fucking fatter. "Why are sperm quality readings dropping in people that aren't obese?" Because the whole population is shifting right and is fatter within their BMI bin. Antibiotics are a real studied cause as well of causing fattening. Frankly it would be extremely surprising to me if we didn't see the outcomes in obesity that we are seeing given the dietary crises the world is facing. Microplastics need not appear in this picture.

titzer 5y ago
> "Why are sperm quality readings dropping in people that aren't obese?" Because the whole population is shifting right and is fatter within their BMI bin. I can't make sense of this statistically. Bins are just arbitrary cutoffs on a distribution. It's not like people know where the lines of bins are and crowd up against the edge, throwing off the median inside. People shifting "within" a "bin" doesn't change much. Instead, people shift bins. Some bins have more people, some bins have fewer people. I think obesity is a huge factor, maybe 80%. But I don't know why you feel so strongly that every other explanation is completely false.
- spywaregorilla 5y ago
  It's a minor argument for something that tends to come up. It's come up a few times on HN some studies that show sperm quality is much lower in obese men, and that there are more obese men. There also tend to be small effect sizes that suggest within the healthy weight bin, sperm quality has dropped a small amount over time. But its naive to think that this means it still isn't a weight effect. The bin argument is basically saying that if the entire population gets fatter, you would expect the average weight within a bin to go up, even if some people move into the next. This depends somewhat on the shape of the curve, and the bins. But on a whole it's simply saying that the average weight of people between X lbs and Y lbs is higher than it was before. Really what it's saying is that the bins obfuscate what could be better analyzed as a continuous variable effect. The bins are arbitrary and misleading. People can fall within the same bin at t1 and t2 but be fatter at t2. > I think obesity is a huge factor, maybe 80%. But I don't know why you feel so strongly that every other explanation is completely false. The evidence and effect size is simply extremely strong, and the prevalence of obesity is very high. I estimate obesity to account for more than 90% of the sperm effect and diet to account for more than 90% of the obesity effect. I'm not opposed to the idea that plastics might have some small single digit effect size. Nor am I opposed to the idea that we might see an inflection point where more plastics start being significantly worse. But for now, it seems to be a tiny, unimportant part of the story.
  - titzer 5y ago
    > The bin argument is basically saying that if the entire population gets fatter, you would expect the average weight within a bin to go up, even if some people move into the next. This depends somewhat on the shape of the curve, and the bins. But on a whole it's simply saying that the average weight of people between X lbs and Y lbs is higher than it was before. It does depend on shape of the distribution, but it is generally not the case that the average within a bin will go up. It is certainly not true for a bell curve, where if you push the curve out to the right (and flatten it), some bins will have higher averages (because they are weighted more to the right than before), but some bins will have lower averages (because they are weighted more to the left than before). If we wanted to go way deep on this, it really depends on the second derivative of the curve within a bin, not even the first derivative (a flat or even straight line through the bin will always give an average right in the middle).
collegeburner 5y ago
Ok then explain why the testosterone reference ranges have went from like 800-2000 in the 60s to 200-800 now. Not just obese people, a "normal" healthy young man these days has the test levels of like a 60-80 hear old then. I think it's something more than just obesity causing endocrine disruption.
- spywaregorilla 5y ago
  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.
- jijji 5y ago
  Here is a story [0] to support your claim, with testosterone levels declining 1% per year on average [1] [0] https://www.forbes.com/sites/neilhowe/2017/10/02/youre-not-the-man-your-father-was/?sh=62b71ff38b7f https://www.forbes.com/sites/neilhowe/2017/10/02/youre-not-t... [1] https://www.reuters.com/article/health-testosterone-levels-dc-idUKKIM16976320061101?edition-redirect=uk https://www.reuters.com/article/health-testosterone-levels-d...
  - spywaregorilla 5y ago
    I found this during my own research but did not agree with the conclusions in the reporting. Here's a paper by the same author: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579652/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579652/ Table 4 has the highlights. An extra 10 years of age has an odds ratio of 1.4 and a p value of 0.02. A 10 cm increase in waist size has an odds ratio of 1.9 and a p value less than 0.001. That is to say, this same author found waist size was a stronger predictor of testosterone than age. This study occurs a few years after the one referenced in the article. Here's the actual study which does make the claim that these factors are insufficient on their own to explain age-normalized t levels. Personally I'm not totally convinced by their methods to control here. It's surprising to me that the later cohorts studied were seemingly the same weight but had poorer health metrics for one. The initial cohort also had an age range of 47-71. The later cohort had an age range of 57-80. The average age being 10 years older. I'm not convinced their mixed effect linear model is going to get a good comparison between these too. https://academic.oup.com/jcem/article/92/1/196/2598434?login=false https://academic.oup.com/jcem/article/92/1/196/2598434?login...
dehrmann 5y ago
It seems like we've discovered things that are obviously bad for us within a decade or two of use. Leaded gas, DDT, ionizing radiation, asbestos. I'm sure there are loads of things that are less than ideal, but it looks like they're all at least an order of magnitude safer than bad things that came to use in the 20th century. It's at a point where the data has problems with statistical significance and confounding variables.
- spywaregorilla 5y ago
  I would be very wary about that. Plastic seems highly likely to be the kind of thing that will, at some level of bio accumulation, cause cancer. I just don't think it's a substantial factor in obesity or sperm declines at the moment.

titzer 5y ago

> "Why are sperm quality readings dropping in people that aren't obese?" Because the whole population is shifting right and is fatter within their BMI bin. I can't make sense of this statistically. Bins are just arbitrary cutoffs on a distribution. It's not like people know where the lines of bins are and crowd up against the edge, throwing off the median inside. People shifting "within" a "bin" doesn't change much. Instead, people shift bins. Some bins have more people, some bins have fewer people. I think obesity is a huge factor, maybe 80%. But I don't know why you feel so strongly that every other explanation is completely false.

spywaregorilla 5y ago
It's a minor argument for something that tends to come up. It's come up a few times on HN some studies that show sperm quality is much lower in obese men, and that there are more obese men. There also tend to be small effect sizes that suggest within the healthy weight bin, sperm quality has dropped a small amount over time. But its naive to think that this means it still isn't a weight effect. The bin argument is basically saying that if the entire population gets fatter, you would expect the average weight within a bin to go up, even if some people move into the next. This depends somewhat on the shape of the curve, and the bins. But on a whole it's simply saying that the average weight of people between X lbs and Y lbs is higher than it was before. Really what it's saying is that the bins obfuscate what could be better analyzed as a continuous variable effect. The bins are arbitrary and misleading. People can fall within the same bin at t1 and t2 but be fatter at t2. > I think obesity is a huge factor, maybe 80%. But I don't know why you feel so strongly that every other explanation is completely false. The evidence and effect size is simply extremely strong, and the prevalence of obesity is very high. I estimate obesity to account for more than 90% of the sperm effect and diet to account for more than 90% of the obesity effect. I'm not opposed to the idea that plastics might have some small single digit effect size. Nor am I opposed to the idea that we might see an inflection point where more plastics start being significantly worse. But for now, it seems to be a tiny, unimportant part of the story.
- titzer 5y ago
  > The bin argument is basically saying that if the entire population gets fatter, you would expect the average weight within a bin to go up, even if some people move into the next. This depends somewhat on the shape of the curve, and the bins. But on a whole it's simply saying that the average weight of people between X lbs and Y lbs is higher than it was before. It does depend on shape of the distribution, but it is generally not the case that the average within a bin will go up. It is certainly not true for a bell curve, where if you push the curve out to the right (and flatten it), some bins will have higher averages (because they are weighted more to the right than before), but some bins will have lower averages (because they are weighted more to the left than before). If we wanted to go way deep on this, it really depends on the second derivative of the curve within a bin, not even the first derivative (a flat or even straight line through the bin will always give an average right in the middle).

collegeburner 5y ago

Ok then explain why the testosterone reference ranges have went from like 800-2000 in the 60s to 200-800 now. Not just obese people, a "normal" healthy young man these days has the test levels of like a 60-80 hear old then. I think it's something more than just obesity causing endocrine disruption.

spywaregorilla 5y ago
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.
jijji 5y ago
Here is a story [0] to support your claim, with testosterone levels declining 1% per year on average [1] [0] https://www.forbes.com/sites/neilhowe/2017/10/02/youre-not-the-man-your-father-was/?sh=62b71ff38b7f https://www.forbes.com/sites/neilhowe/2017/10/02/youre-not-t... [1] https://www.reuters.com/article/health-testosterone-levels-dc-idUKKIM16976320061101?edition-redirect=uk https://www.reuters.com/article/health-testosterone-levels-d...
- spywaregorilla 5y ago
  I found this during my own research but did not agree with the conclusions in the reporting. Here's a paper by the same author: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579652/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579652/ Table 4 has the highlights. An extra 10 years of age has an odds ratio of 1.4 and a p value of 0.02. A 10 cm increase in waist size has an odds ratio of 1.9 and a p value less than 0.001. That is to say, this same author found waist size was a stronger predictor of testosterone than age. This study occurs a few years after the one referenced in the article. Here's the actual study which does make the claim that these factors are insufficient on their own to explain age-normalized t levels. Personally I'm not totally convinced by their methods to control here. It's surprising to me that the later cohorts studied were seemingly the same weight but had poorer health metrics for one. The initial cohort also had an age range of 47-71. The later cohort had an age range of 57-80. The average age being 10 years older. I'm not convinced their mixed effect linear model is going to get a good comparison between these too. https://academic.oup.com/jcem/article/92/1/196/2598434?login=false https://academic.oup.com/jcem/article/92/1/196/2598434?login...

dehrmann 5y ago

It seems like we've discovered things that are obviously bad for us within a decade or two of use. Leaded gas, DDT, ionizing radiation, asbestos. I'm sure there are loads of things that are less than ideal, but it looks like they're all at least an order of magnitude safer than bad things that came to use in the 20th century. It's at a point where the data has problems with statistical significance and confounding variables.

spywaregorilla 5y ago
I would be very wary about that. Plastic seems highly likely to be the kind of thing that will, at some level of bio accumulation, cause cancer. I just don't think it's a substantial factor in obesity or sperm declines at the moment.