Not exclusively, of course, but the degree of processing of food greatly influences our body’s insulin response, which can over time have huge impacts on health (leading to fatty liver disease / metabolic syndrome / obesity / diabetes). This is why, for instance, fruit juice is so much worse for us than the whole fruit — most of the fiber is removed which would otherwise slow down digestion and temper insulin response. For more info I’d highly recommend Jason Fung’s Obesity Code book — he’s a nephrologist specializing in diabetes treatment.

Categorically? Absolutely!

But as humans we can't read every study for every ingredient. We have to use heuristics to guesstimate a healthy diet. Reducing (not eliminating) processed foods is a decent one. Same goes for including protein, increasing fiber (so whole wheat instead of the cake americans call "bread"), including veggies.

This source says differently [0], at least for meat. Do you have any evidence or reasoning?

[0] https://pubmed.ncbi.nlm.nih.gov/18444144/

What makes you think so? Do you have any examples of particularly healthful highly processed foodstuff in mind? Or is this more some "there are no slow programming languages, only slow implementations" type of argument about the absence of strict logical necessity?

Healthy food is basically a lemon market, so what would a plausible mechanism to economically incentivize high processing for healthfulness look like?

Conversely there is a clear economic incentive to highly process food in order to decrease unit cost at fixed palatability. By increasing yield (pink slime) or shelf-life (trans-fats) or taste and looks (flavor enhancer etc).

None of these are necessarily bad in all cases, and in some cases might even correspond to increases in healthfulness (e.g. by killing harmful micro-organisms).

But on average, in the absence of some additional economic incentive to keep or increase healthfulness, I'd expect optimization for these criteria to decrease it.

For example, a lot of nutrients have short shelf-lives, so if there is an incentive to increase shelf-life but not an equal incentive to preserve nutritiousness (and I don't think there is), you'd expect healthfulness to go down, no?

Saying there's necessarily a causal relationship is probably not well supported, but there's absolutely a correlation, and as a rule of thumb, if you choose whole foods over processed foods it will tend to net out as more healthy.

Nutrition pretty much by definition requires a lot of simplification to allow people to make quick decisions on food choices, and so broad rules that are mostly right are pretty useful (and pretty much the basis of how most diets work).

You are technically correct. However...

The complexity of digestion rivals that of cryptography. And the same caveats apply.

Ultraprocessed foods, let's say a [plant] burger, are the food equivalent of "roll your own crypto".

Less processing = fewer things we break without knowing we broke them. I'm in no way actually arguing against cooking.

This would take a fair bit of time and space to explain in general, but if you have specific questions I'll do my best to address them.

I agree in so far that I believe that the observation of "more processing > less health" is not caused directly by the amount of processing, but by the way those highly processed products are designed to match as many "appetites" as possible. I use the term "appetites" in the sense of a low intensity craving, the feedback signal the body sends to fill some nutrient deficit. But our taste buds can't really identify most of the nutrients in question, we just have is a set of complicated heuristics taking an educated guess. And many of those highly processed foods, in their quest to maximise desire, will fool those heuristics, matching the "appetite" without fulfilling the deficit. Perhaps not by deliberate design, but by market selection.

On one hand, the faux meats sound quite risky, but in the other hand they are under extreme scrutiny like no highly processed food before them, so they might not actually be bad at all.