History is full of huge disasters where absence of proof of negative effects was seen as proof of absence of negative effects. PFAS are such an example. There are already proven negative effects, many correlations are probable causations because we have good explanations like endocrine disruption for them, and worst of all bioaccumulation means that we cannot turn the clock backwards and all the more reason to use the precautionary principle.

All chemicals should be considered dangerous without any other knowledge. Coevolution of humans with chemicals (which has a big overlap with “natural” in contrast to synthetic chemicals) is just a prior that makes danger less likely.

Yeah... I'd love to see a "reset" to foods that were generally available 150 years ago. Before industrialized foods were broadly available. Meat, Eggs, common veg, and pre-gmo grains and legumes. And kind of start over. I understand modern farming allows the world as it is to be fed... but there's plenty of room for states/countries that are able to financially to try to do much better.

> reduced time between meals not allowing people to exercise their lipid transport in reverse.

I hadn't heard of this before, but it's interesting; despite receiving guidance to consume smaller, more frequent meals, I've found the practice has a negative effect on my own energy levels and weight stability.

Would you mind elaborating on this point, or providing links to further reading?

It is called fasting. It has been practiced for entirety of human history in all societies except for last couple of decades.

Fasting is an opportunity for the body to burn stored fats. Insulin is a hormone that tells every cell in the body to take sugars from the bloodstream and effectively prevents burning stored fats. When cells are used to burning sugars all the time, when given access to sugars and fats they will chose sugars preferentially. So as long as they have supply of sugar there is very little fat burning happening.

What's more, when you stop eating for a moment, for whatever reason, your body still does not have ability to burn much fat for energy because the metabolic pathways to do it are too dormant to provide enough energy on a moments notice. You become hungry which is your body telling you it can't get energy and you resolve the only way to fix the issue is by putting more carbohydrate-rich food in your mouth.

Fasting periods are necessary for the body to train those metabolic pathways. For example, by eliminating breakfast and not snacking in the evening you can easily double the time it takes between two meals giving couple of hours each day during which your body has to get energy from the fats. Over time your body relearns to burn fats and when you don't eat for a moment for whatever reason it is able to start burning fats faster and start providing more energy lessening the feeling of hunger and immediate need to put more food in your mouth.

Fasting is the normal state of the human body. We have evolved in conditions where food was relatively scarce and when we finally caught something, we had to eat it here and now and then move on and wait until we are able to catch something else at unknown future time.

This means we have evolved to accept food for a relatively short portion of time, be very good at storing energy as fat and then to use this fat for a long time until we could catch something else.

Very interesting, thank you!

This correlates perfectly with my experience: When I've tried to incorporate breakfast or other frequent small meals into my diet, I've found it wreaks havoc on my energy levels and feeling of fullness throughout the day. Without attempting to "fast," I've found that I feel best and experience fewer "crashes" when I skip breakfast and after-dinner snacks. You've just explained a convincing reason why that would be the case.

Next level is removing most or all carbs from your diet and restricting your eating window to a short time every day, no more than 4 hours. Which is what I do besides longer fasts.

I now don't even need to eat every day -- I had situations where I skipped entire days of eating because I simply forgot about it.

If you think about it most people have hundreds of thousands of calories on them in form of a huge fat layer covering most of the body which is enough for even lean people to live off for weeks at a time. If you think about it, it is pretty silly to complain one is hungry when there is so much energy stored on us.

I remember this thought struck me when I was reading about first Inuits trading in Canadian outposts. They would sell their furs and buy food. When a curious scientist decided to follow them he discovered they would stop outside the outpost, eat ALL food they just bought in one huge binge and then travel back home for many days or even weeks without eating anything. They were not only good at storing fat, but they were also good at recovering the energy when they needed for however long they needed. This is what means to be fat adapted -- being able to completely separate intake of food from burning stored fat for energy.

People nowadays are like a car that does not have a tank for gas. You have to keep pouring the gasoline into the engine constantly or it will shut down. What you want is a large tank from which you can be constantly supplying energy to your engine but you can fill this tank at your convenience.

Yeah. But no. I naturally seem to eat once a day and am thoroughly overweight.

And this is meant to be proof of what exactly?

Somehow doing one thing right is supposed to prevent obesity in every single case?

That all obesity must necessarily be because of people eating multiple meals?

And you're not losing weight? What/how much are you eating?

>Correlation does not imply causation

Correlation does not guarantee causation. But the stronger the correlation, the more you suspect that two phenomena are causally linked somehow. In this case, three pounds over half a year is a surprisingly large effect. If it were to continue, even if it slowly approaches an equilibrium, it could be responsible for a substantial increase in total body weight in millions of people. It's very possible that PFAS is just acting as a proxy for exposure to packaged foods, but that would be interesting in itself.

In this case, the best course of action is to study the phenomenon more closely, mostly because it is large.

Causal link requires an investigation to understand what is the nature of the link.

Is it possible that people who are likely to be more obese are also likely to eat garbage food delivered in low quality plastic packaging? And more healthy people are more likely to cook their food from higher quality ingredients like fresh produce that is not delivered in plastic?

See, the above explanation, I think very reasonable (though requiring a proof), could explain why obese people could have higher PFAS?

Another possible explanation (again, I am just sayin', no proof for it): imagine all food is contaminated with PFAS, but obese people have different chemistry that is worse at removing PFAS from their bodies.

This is why we say "correlation does not imply causation". Yes, highly correlated things are interesting and require further investigation. Even if PFAS is not causing obesity we still might learn something interesting about either PFAS or obesity or something else that is connected to both.

> Again. Missing big fat disclaimer. "Correlation does not imply causation". It is wrong to jump from "Weight loss relapse associated with exposure to perfluoroalkylate substances" to "Obesogenic PFASs may cause weight gain and thus contribute to the obesity pandemic".

That's correct, but it's interesting to ask: what should public policy be in light of these findings?

None? There is nothing actionable here.

We already know PFAS are dangerous for other reasons and the war against them is warming up.

And policy is not/should not be made based on just one study. Sadly, there are too many contradicting studies. Things like this need to be re-checked so that policymakers and societies don't waste time chasing things that don't bring any results.

Even then, we need to understand what is magnitude of this effect, what level of PFAS translate to what increase in obesity risk, etc. Then put it in context of already planned PFAS reductions.

Then if I was policymaker I would also look at what are potential projects we are not working on and where are highest return on investments. Just because there is something you can fix doesn't mean you should fix it. There might be another thing with more ROI where you should be spending your efforts.

That is assuming the conclusions of this study are correct, which I don't believe they are.

The findings of this one study should be rigorously evaluated and replicated first, not that much of our public policy is based on any kind of evidence but that would be the right way to go about it.

You mean, it's correct that the facts are not actionable, but what should we do?

Of course the switch off to the likes of margarine, seed oils and other high omega-6/3 ratio fats doesn't help. Was just looking up the cost of Beef tallow, say if someone did want to try to convince a restaurant to switch back and it's now 5x the cost of the "vegetable" seed based oils. It may last longer in a commercial setting, but that's a hard pill.

You are right. Just because food is fatty doesn't mean it is healthy. I did not want to make the comment too long but there is the concern for the quality of fats which is pretty complicated problem. There are some simple rules -- for example you definitely want to stay away from highly processed fats. But further than that things get more complicated.

As an example, we are told that fish is generally one of the healthiest fats around. But what people forget is that this is assuming wild fish and the kind that does not accumulate rare metals. Salmon is pretty health... unless we are talking farmed salmon. Farmed salmon is fed with highly processed, carbohydrate-rich feed which completely changes the fat content of the salmon making it very high omega 6 to 3 ratio. And God knows what else...

Beef tallow -- I have simple solution for this at least for my home use. I buy lots of quality red meat. Whenever I may broth or render fats for any reason, I gather them all and store them for later.

That's cool.. honestly, when I've made beef broth myself, it never really tastes that good. But I will do a filter through a fine mesh chinoise, and take the fat out as it settles to cook with. I do try to keep about half my meat/egg intake "clean" (pasture raised, etc) but it can be cost prohibitive sometimes.

I can make good tasting beef broth but I usually don't even bother.

I make a huge, 15L pot of broth. I use various pieces of meat, especially ones that have a lot of collagen. If I think I have too little cartilage I will add achilles tendons which are pretty much pure collagen. I brown everything them either on a pan or in the oven and I simmer it for at least 12h until all meat disintegrates and all collagen and fats dissolve. I then remove and discard meat and bones and small particles by filtering it through fine mesh strainer, I remove (and store) the tallow. And then I reduce everything about four-five times to get the meatiest substance on Earth. Cool it down, it should completely congeal in room temperature. I cut it into cubes, throw it into plastic bags and into the freezer. Then whenever I want to make soup or a sauce or risotto or whatever else, I just take some cubes from the freezer and drop directly into the pan or pot.

I also make and freeze other useful things. For example, I always keep a supply of bolognese sauce which I make 9L at a time and then lasts me for a year.

Yeah, my SO has been volunteering with a charity that does a feed the homeless thing on Saturdays, so have a lot of staple items around... Though making from scratch takes effort, it does cost a lot less at anything resembling scale, even for a few hundred portions once a week. Basically she spends 2-3 days a week just on food prep. I help when/where I can.