"We found weak evidence of ..." becomes "New study ABSOLUTELY DESTROYS the myth that..."

I see this claim semi frequently online. So I'll just ask.

What is meant by "processed"? What does it mean to be "worse" (Worse than meat? Regular foods?) What is meant by "whole foods"? And finally, what's the evidence for these assertions?

Is black tea a processed food? How about coffee grounds? When does something cross the rubric of processed vs unprocessed?

To me, it's not obvious that "processed is bad" particularly because I don't know what "processed" means.

As a side, how do fortified foods fit in with processed foods? Iodine in salt, for example, has been a huge public health success. Goiters have practically been eliminated as a result.

When people use the term "processed foods" colloquially they are generally referring to NOVA group 4, ultra-processed foods. It seems that that group is implicated in worse health outcomes and it is also that group that has proliferated the most significantly over the past 40 years in tandem with rising rates of obesity and poor health outcomes.

The term is quiet loose.

And I'd agree, that category does generally seem to be an issue. Though, I have to wonder if it's more a problem that that category typically has foods with an absurd amount of calories that are easy to consume.

For instance, pure peanut butter is unprocessed. While it runs through a mechanism to change it from peanuts to peanut butter, there is no oil added, nor are any of the healthful nutrients of peanut butter extracted. Opposite to this is peanut butter like JIF which is processed - the mix is diluted with sugar and vegetable oil to make the same amount of food for cheaper.

Same with tofu - it starts as soybeans and is ran through a mechanism to turn it into the blocks of tofu we see in stores, but we do not add sugar or oils to change the contents of that block, nor do we remove nutrients from the soybean (this may not be 100% accurate, but generally speaking, nutrients are not removed in this). However, many vegan meat products put a lot of unhealthy additions into the mix, thus making it processed.

Even if I accept that "Processed foods are more or less the only remaining food-based explanation." My questions really boil down to "what are processed foods" and "What's the evidence they are bad"?

The study includes an appendix with photos of all the meals - it's very interesting!

The evidence suggests that various qualities of ultra-processed foods drive overconsumption. There is also speculation that the calories in ultra-processed foods are more bioavailable than those in less processed foods because ultra-processed foods are easier to digest due to their low fiber content, though I don't have any evidence for than on hand (will update if I find it).

Definitely send more studies if you find them. This one seems to suggest the main problem with ultraprocessed foods is they are easier to over eat (they taste better? Are less filling?) but it doesn't really show that they are necessarily bad.

Seems to jive with how food works for me. I've been counting calories as of late and it's definitely easy to down a bag of doritos or drink a bottle of soda

Have you heard of Stephan Guyenet? His book The Hungry Brain is a good read on the neuroscience of obesity. He proposes that eating highly palatable calorie-dense foods changes the brain in various ways that ultimately drive us to consume more of those foods and to have difficulty changing our eating behavior. Unfortunately his suggestion is to eat an intentionally bland diet, which is obviously unappealing, but my anecdotal experience is that highly palatable but less processed foods (e.g. a wheel of brie) are far more satiating than similar but ultra-processed foods (e.g. queso made from velveeta).

I'm not sold on the idea that we need to eat bland foods, or only foods familiar to our hunter-gatherer ancestors, or only plant products...it seems to me that we only need to go back 50 years or so to before the dramatic rise in obesity started, which points toward avoiding ultra-processed foods. I hope we get more studies on this eventually!

Note that I'm not saying we should do this - I believe obesity is much more likely caused by a wide array of lifestyle factors that no study to date accurately controls for (including diet, exercise, stress, environmental factors, mental status, medication etc), not a single dietary style.

Now, "processed foods" is indeed a very vague term, and people tend to include/exclude different foods based on their pet theory of what may lead to the link "observed" in the previous paragraph.

For example, some people strongly believe that glycemic spikes are strongly coupled with diabetes and obesity, and they would include things like fruit juices (as opposed to eating whole fruits) into this category, as well as high glycemic index foods such as bread (in both cases, even home-made ones).

Other people believe that certain additives are likely to have undocumented side-effects, so they will tend to only include foods with synthetic additives, such as preservatives and food colouring, but exclude traditional highly processed foods such as bread or butter as long as they are home-made without additives.

Yet other groups believe the correlation is related to palatability and/or satiety, so they will consider processed foods to be any foods which contain high ratios of palatable substances (like fat, sugar, salt, MSG, other flavour enhancers) to less palatable macro-nutrients. These people would probably include home-made fruit juice or ramen into the processed foods category, but may exclude things like pickles.

If it's unreasonable to pin down what is processed, it seems unreasonable to make a claim about the effects of processing.

Our understanding of nutrition and health isn't keeping up in pace with innovations in the food industry. And due to the scale and depth of it I think it's unavoidable that many small bad things will sum up over time leading to health problems without a clear root cause.

Reasons why "processed" food might be bad for health:

- skewed omega-3/omega-6 ratio

- micro-nutrients depletion

Also it's just not economical or environmentally sustainable to feed everyone with "real food". At least not without radical change and trade-offs in other areas.

> Processed meat – meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavor or improve preservation

> Red meat – unprocessed mammalian muscle meat such as beef, veal, pork, lamb, mutton, horse and goat meat

> Consumption of processed meat was classified as carcinogenic and red meat as probably carcinogenic after the IARC Working Group – comprised of 22 scientists from ten countries – evaluated over 800 studies. Conclusions were primarily based on the evidence for colorectal cancer. Data also showed positive associations between processed meat consumption and stomach cancer, and between red meat consumption and pancreatic and prostate cancer.

When they talk about causing cancer they're talking about two things: the quality of the evidence, and then the strength of the effect.

For processed red meat the evidence is very strong: processed red meat does cause colorectal cancer.

But how much cancer does it cause? It doesn't appear to cause much cancer. If you have a genetic predisposition to colorectal cancer, or if you want to be very cautious, you might want to think about avoiding processed red meat. But otherwise, well, the small increase in risk might be worth it for the benefits you get from eating food you enjoy.

In the case of meat I think it's usually referring to added nitrates as a result of processing, which is linked to health problems [0].

> To me, it's not obvious that "processed is bad" particularly because I don't know what "processed" means.

Yeah I think your point is valid - "whole" is a bit like "natural". Too broad and undefined. We're supposed to think one is good and one is bad because marketing of "whole" and "natural" is trying to create that impression. No-one says "chemical" in their marketing, like no-one says "processed". You only advertise as "natural" or "whole".

[0] WebMD, but there's loads of articles about it https://www.webmd.com/diet/foods-high-in-nitrates

I think the closest you can get to a "real" definition is food that has added ingredients, usually oils or preservatives, not found in traditional cooking. Usually these are added more for reasons of shelf-life or in order to cram in extra taste, or both.

But this is very, very weak evidence.

edit: of course I have to assume something about the structure of the data to say it's very weak evidence. It may be very strong evidence of a very weak effect.

Right, because the results of the previous studies amount to evidence that is too weak to conclude that red meat is inherently unhealthy to consume. I'm not sure how your comment contradicts this.

> The available evidence suggests that eating no unprocessed red meat may minimize the risk of disease incidence and mortality compared to consuming any, but there is insufficient evidence to make stronger or more conclusive recommendations. More rigorous, well-powered research is needed to better understand and quantify the relationship between unprocessed red meat intake and chronic disease.