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Comment by spywaregorilla | Hacker News Reader

This comes up every now and then, and I take a look at some research and it always seems pretty clear that it's obesity.

edit: the phthalates comes up every time. Yeah it does seem to have some effect, but the effect sizes found in papers doesn't seem to be that huge, meanwhile the effect size of obesity is very large, and the prevalence of it is observably growing rapidly. You also have to consider that the people with the most bioaccumulant shit like this are the people with large reserves of fatty tissue to absorb it.

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BPA/BPB in plastics is another source. Unfortunately, this one is basically unavoidable since even if one doesn't own any of those plastics at home, there's bound to be some food product that uses a plastic container. Even more so, we don't know anything about how long it takes to leach into the food, what plastics do/don't contain it, stuff like that.

Plastics should just be banned from touching food entirely.

I think it really depends on the food. Like processed or skinned meat absorbs more than seeds or dry food, frozen absorbs less, or something like that. I haven't read about it for a while but that's what I remember was kind of like the consensus about where to start looking into if it's feasible to ban BPA.

If you have running water in your home, every drop likely flows through hundreds of feet to miles of plastic pipe before you drink it. Even if you have a private well and copper plumbing, your pump and other components almost always contain plastic parts that make contact with the water.

An interesting series of articles that came up on HN a couple months ago makes the argument that both infertility and obesity arise from environmental contaminates (although not necessarily phthalates). Regardless of whether you agree with the arguments presented, I think it’s really interesting to see just how complex of a problem it is to figure out what’s going on.

https://slimemoldtimemold.com/2021/07/07/a-chemical-hunger-p...

I don't particularly buy it. Again, sure, maybe it has a statistically significant effect, but it is undoubtedly dwarfed by people chugging sugary drinks and being more sedentary. A casual search suggests sugar consumption has increased 9 fold since the 1800s and 2 fold since the 1900s. The poor in particular are cornered into purchasing sugary foods due to weird economics around corn subsidies. And what do you know? They're the fattest by far.

If it were mostly environmental you'd see broader gains. variation. But in my little bubble in upper middle class Massachusetts, I don't know ANYONE who is obese. In other areas of the country it's hard to find anyone who isn't.

The linked site does suggest a reason Massachusetts would have less overweight people, based on their exposure to environmental contaminants.

Sure. But you'll find plenty of fat people in poorer areas of massachusetts.

Maize fructose has probably a bigger effect than cane sugar, because it also hit poor populations.

Well, if we control the epidemics of sedentarism and obesity doesn't follow, those complex causes may be worth investing on. But we have a very simple pair of problems (bad nutrition and sedentarism) that are able to explain more than all the obesity around without any need for a contributing cause.

(Anyway, the odds that there isn't any contributing cause on the tons of changes we made on the world are pretty small, and it's important to study those for individual health. It's just for societal health that there's no mystery to solve.)

The second article in the series cites a 25% increase in calories consumed during the period where obesity is rising, but then tries to wave that away as inconsequential.

It seems obvious that obesity is the result of the increased caloric intake with secondary effects from the increasingly sedentary lifestyles we all lead.

Environmental toxins might play a tertiary role, but it’s definitely the calories driving most of the obesity issue.

It does seem painfully simple that consuming more energy than you burn/excrete is going to turn you into a sink, and a lot of that surplus energy is going to be stored as fat. (And the opposite process applies when you consume less than you use.)

Is this an oversimplification, or is the average education/propaganda/understanding so confused, and so overwhelmed with different nutrition ideas that the wood is being missed for the trees?

I read that blog series and it makes a decent case that there is some environmental contaminant that matters (or a combination of several), but it can't be the whole story because things like gastric bypass definitely work. Also just from observing obese people eat it is clear that few of them eat in a way conducive to weight loss. Perhaps some environmental contaminant causes them to crave calorically dense, non-satiating foods, but that seems doubtful to me.

Edit: The other thing I noticed when reading the series was that the author had a habit of discounting anything that refuted his thesis (calling it a minor effect and so forth), while giving greater credibility to similarly weak evidence for his theory.

Incidents like this, small remote populations along the Amazon in Brazil rapidly becoming fat when given access to nestle food; make me think it's just the food (in practical terms).

https://wearemitu.com/wearemitu/things-that-matter/nestle-fl...

People who eat meat and animal fat and cut out sugar report getting pregnant after years of not being able to. They also report iso-caloric weight loss, resolution of diabetes 2, thickening of hair and many other positive health heuristics. Obesity, diabetes and metabolic considerations are an absolute powder-keg of medical progress just waiting for mainstream acceptance

The people getting pregnant after eating meat are unlikely to be men.

It seems like a combination of issues.

The obesity thing tends to hold across many other species too. I would guess you are right about this being the main driver. A classic example would be dealing with animal husbandry and obese pigs. Fertility in obese females can be impacted too.

A variety of toxins have been shown to cause fertility issues too, such as lead and pesticides. It's also possible that estrogen and estrogen mimicking compounds found in drinking water could fall into this category (estrogen can adversely affect male fertility).

Testoterone is also a factor which has seen a large decline over the last 50 years. Obesity and sedentary lifestyle can cause a decline in testorerone and other hormones/enzymes related to sperm.

Then there's a possible link to RF reducing sperm quality. Although I think this is probably a secondary factor that might exacerbate the others.

That's an interesting idea, but I'm not sure the anatomy lines up. Like the mass of belly fat and fatty liver pressing down from above in upright humans resting on the pudendal artery wouldn't be the same as how the mass hangs on quadrupeds. This is an interesting line of thought too, like what organs get compressed under gravity from increased mass assuming it's primarily a mechanical problem.

I'm not talking about anatomy, but rather physiology (obesity affects hormones related to sperm). Do you have some information to suggest this is an anatomical issue (other than sleep apnea) rather than physiological one?

nothing specific other than speculating about hearing about stuff around that bottom part of the body: lower sperm count, slower bowel movements with constipation and stuff. I wonder if there's anything else anatomical down there that could potentially get disrupted from extra mass bearing down on it.

There is probably some bidirectional causality between decreasing T levels and rising obesity.

I think that's pretty firmly established. It's also a leading cause of ED.

So is circumcision.

That's the opposite of firmly established. I say that as no fan of the practice.

It took me a few seconds to realize your comment was a pun.

I thought I remember reading it is dropping across the line, including for fit and healthy individuals. Is that not right, and if it is, what could that mean?

Sorry for lack of source, it’s not my area.

I can recall only one article that was posted here which included that, but I came away thinking it was misleading. It binned weight categories(e.g. BMI ranges from X-Y) and showed that over time, people were falling into heavier categories, and that sperm outcomes were getting worse in every category (heavily in the obese, less so in the normal weight range). But if you eyeballed the curve it felt very likely that the distribution of individuals was just shifting the the heavier end within each category.

E.g. if a healthy BMI is 18-25, and you look at the the average outcome for that group over time... if the whole population gets fatter then the mean value in the 18-25 group could shift from 20 to 22. So... take it as you will. Sorry for no source here either.

If obesity it perhaps should be studied as a realtime pushback against modern diets by nature/natural selection, in reducing unhealthy people from the gene pool.

Obese people are not intrinsically unhealthy. They're usually just unable to access reasonable nutrition.

Risks for cardiovascular disease, stroke, cancer, and of course diabetes, are all significantly increased with obesity. Risk of getting severe covid-19 is significant increased with obesity.

I know plenty of relatively wealthy people who are fat or even skinny fat (arguably worse condition), it's not only about access to reasonable nutrition.

Or perhaps the correlation between obesity and low fertility is not causation, obesity could very well be a symptom of whatever is causing it, alongside low fertility.

Obesity is fairly well documented to cause poor fertility in animal studies

Do you have any links? Offhand I would suspect exercise, but I guess that's hard to differentiate from obesity.

Studies correlating obesity and poor sperm quality are numerous and easy to find.

https://www.hsph.harvard.edu/news/hsph-in-the-news/excess-we...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3521747/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5657098/

You can find more without much effort. What I don't see are epidemiological studies trying to track the prevalence of obesity vs. the average sperm quality across different nations. Unfortunately.

I always thought it was the rise of porn

Why would that increase infertility?

From a purely observation perspective, pornography consumption has increased dramatically at the same time as falling fertility. Even if a mechanism isn't obvious, it at least seems like there is a possibility of a connection.

Studies have indicated that long-term pornography use correlates with erectile dysfunction and loss of interest in sexual relationships. It's not hard to imagine that fertility might be related to these other aspects of reproductive health. Unfortunately few long-term studies seem to focus on fertility specifically.

Short term studies on the influence of porn find that novel sexual stimulus seems to increase sperm quality while it attenuates in response to repeated exposure to the same stimulus. This is bad news for real life humans who cannot change as rapidly or dramatically as one can switch videos.

> Why would that increase infertility?

Indeed ... wasn't it supposed to cause blindness?

The lower cost of sexual release in porn leading to less motivation to pursue relationships with the opposite sex, an activity which in our current state of reproductive preferences, moral values and technology is strongly correlated with instances of human reproduction.

you're thinking of ED

That's ED.

P.S. The use of "fertility" to describe men is weird and seems recent. Fertility is passive and receptive and thus better fits women (hence the use in agriculture to describe the earth). Virility is a better term because it is active. Some people seem to falsely claim that it doesn't refer to procreative or generative power, but it does as this entry in Etymology Online[0] shows (emphasis mine):

"period of manhood," 1580s, from French virilité, from Latin virilitatem (nominative virilitas) "manhood," from virilis "of a man, manly, worthy of a man," from vir "a man, a hero," from PIE root wi-ro- "man." Meaning "power of procreation, capacity for sexua[l] intercourse" is from 1590s; sense of "manly strength" is recorded from c. 1600.

There's not much power to procreate if you have a low sperm count.

[0] https://www.etymonline.com/word/virility#etymonline_v_30873

I think "lack of fertility" to design low sperm count/inviable spermatozoids is accurate. Lack of virility would be impossibility to use your own penis for different reasons. 10-8 year ago i knew a trans who was fertile and could give sperm to her lesbian friends, but lacked virility.

The female counterpart of virility should be femininity.

DNA and knowledge of the specific of procreation is probably as recent as the use of fertility.

Wanted to comment about obesity but i guess most people said what i wanted to say, so i'm rebounding on a tangent for my own self-esteem, sorry.

Technically you're right.

But If I was a researcher, I would stay clear of using a term that could be understood as some kind of endorsement of toxic masculinity, heteronormativity or whatever.

Better to use the slightly less accurate term, overloading its original meaning with a new one, and avoid being the subject of a witch hunt.

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