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"?
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.
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!