The more specific you get about a diet, the more specific you need to get about the person eating it. So long as most dietary advice is designed and tested at population scale, it's going to be fuzzy and inconclusive.
Even the most basic advice we can give today comes with asterisks.
I agree. It’s true of many (all?) diets that its proponents tend to overestimate the applicability of any one diet to all people.
Dietary science is at its infancy. Contrary to what most people would assume, we have mountains of anecdotes, mountains of opinions, and very few hard facts. Navigating diet from a fact-first, science-first perspective is deeply frustrating.
It's possible that a) diet isn't that hard to figure out and b) gamifying, quantifying, testing, and over-extrapolation from isolated scientific results make people confused and much less effective at making the right decisions consistently, which is the part they really need help with.
I do agree with your general premise. Most health advice is too complex, and it can all be boiled down to: eat whole foods, mostly veggies. If you must eat processed, the less ingredients the better.
A lot of the confusion also has to do with people treating their diet as religion. Also, there's a lot of misinformation from the government (the normal Food Pyramid is the worst thing to follow if you need to lose weight), and as a result lots of conflict with popular wisdom. As such, when someone gives advice that is different from the norm, people immediately shoot it down as just a fad.
I didn’t ask for it to be universally applicable, or even broadly applicable. Or even applicable to more than the person the question imagines. I asked if we have enough information to know one single example of a healthy diet for one imaginary person who you are allowed to assume has no complicating factors.
Because if we can’t answer this much much simpler problem then we have no hope of giving nutritional advice to a population that is as varied as you describe.
Sometimes it seams that people are interested in these technical and highly specific debates on how to eat right to avoid responsibility. They want to "know" that eating right is so difficult and badly understood that it can't be done without a special diet. When they then select a diet and it works, they attribute it to the diet and not the utmost care that they followed the diet with.
This is a huge problem. Way too much diet advice takes the concept of a "balanced" diet for granted, while descriptions of what that means tend to be at least one of:
1) uselessly vague (eat "a variety" of foods, eat sugar "sparingly", get "enough" fiber, and so on; "eat lots of colors" is actual dietary advice that has been given by credentialed dietitians),
2) driven by some fringe/fad theory of nutrition, or
3) based on unrealistic or parochial assumptions of which foods are readily available/affordable.
This is the annoying thing about diet/nutrition advice, and why "The Hacker Diet" is really appealing to me, even if it's a little simplistic -- it's at least logically consistent and has some rationale behind it, even if it's a flawed one.
Most diet advice is vague and full of generalizations and never backed up. It makes sense, but you hear often opposing viewpoints made in the same hand-wavy fashion. For instance:
Okay, why avoid grains? Are some grains worse than others, or are they all magically bad? Either way, why, and what evidence supports it? Does this apply to any carbohydrate, or just strictly grains? What's wrong with industrial processing, and is there evidence to prove it? Does it apply to everything that could possibly be considered industrial processing, or just certain types of industrial processing that are particularly bad? Is it possible to make up for whatever negative effects it (anything one is advised not to eat) has, and does it apply to 100% of people, or a set of people that you make a set of assumptions about?
I'm not attacking your viewpoint specifically -- I think you're most likely right -- but this is just why I have a hard time believing most diet advice. It's always so wishy washy, and it always brings up more questions.
Another example: advice around drinking soda. There are many types of sweeteners used in diet sodas, and lots of studies done on their effects on humans and other mammals -- none particularly damning. But no one giving nutrition advice will say "avoid ingredient X because Y", they'll say "avoid (vague category of food which may or may not contain ingredient X)". And then someone else will come along and say the opposite. And then there's always some link to some study done in the 1940's that's since been discredited or something.
I think we should be pointing to science - which to date it hasn't been adequately done relating to diet, to see what diet is optimal, and how that varies per group whether that's by blood type, DNA/ancestral data, or other - while taking in the particular sensitivities of each individual as part of the research vs. making the reference points based on a structure of scarcity of what was available based on what people could afford; also having an idea of a person's current health state, how healthy their GI tract is and overall system needs to be taken into account as to how they may or may not respond to different diets - including not limited to how we're only just beginning to understand how gut bacteria and within the whole GI tract can strongly impact outcome.
Especially in the case of diets, I think personal experience should acccount for most of how you make your decisions. The human body is very flexible to different conditions, the science here is pretty flaky, that trying to make sense of diets by using logic only helps very little. Anyway I'm just repeating what you're saying, that personal experience may not be universal but it's important for yourself.
It sounds like you're expecting others to provide complex-but-accurate advice when OP and most of the responders are happy with simple-and-implementable advice. A lot of the discourse around diets comes down to tension between these two.
Simple-and-implementable is something you can deploy in the moment without knowing things beforehand. If you're at a grocery store, you can ask yourself "is this really processed?" as a simple filter that will largely steer you right. Similarly, Michael Pollan's advice to "Eat food. Not too much. Mostly plants" resonates with a huge number of people because it's a simple, actionable, not very fussy way to approach eating.
Complex-but-accurate advice is stuff like 'let me look up if this follows the definition of tier 3 or 4 processed', or 'I have to have 5g net carbs today and this is 1.2g so I have 3.8g left'. This has a much higher cognitive load, requires a lot of research and pre-planning, and is unlikely to be implemented in the moment nor sustained long term. It's also a place where people can develop unhealthy psychological relationships with food and eating by being hypervigilant about complex rules.
Most people find their lives work best with simple-and-implementable rules of thumb for food.
"go with a balanced diet."
As much as I'd like to, it's next to impossible to even figure out what a "balanced diet" is these days. The information conflicts even on something that basic.
I mean it might be a waste of money, but I think part of what they're trying to accomplish is not what's good generally, but also how certain people may respond to different foods, which they hope to leverage for doctors to personalize diet recommendations:
“There can be this public perception out there that ‘Oh, everyone knows what you’re supposed to eat, but it doesn’t work for me.’ But if this is for me and based on me,” people might be more likely to follow the plan, Nicastro said.
Which is not the end all be all for diet advice, but it generally works, and at minimum points people in the right direction. Of course there are edge cases, and other important factors. Consume less and move more is what most people need to do.
Dietary guidelines typically self-moderate to something that they think the populace has a chance of adopting. I.e., they don't want people to completely shrug it off as too drastic of a change.
I would like to see a different approach: show the actual best diet guidelines, and then explain which partial steps will do the most good. Or something like that. It's better to be up front with what's known and then proceed to harm reduction rather than telling people that these partial steps are where they should end up.
The point is we don't know, which is the case with most lifestyle/diet choices that aren't obviously bad in a vast majority of cases, like smoking and overeating.
Anyone trying to personalize their optimal nutrition is already in the top 5% of Americans in regards to healthy eating. We are so, so, so far from even baseline semi-ok diets in the most generalized all-of-humanity guidelines.
To believe the typical developed nation's dietary guidelines are the best advice on a healthy diet is to show a level of credulity and lack of critical thinking as silly as thinking paleo is rebranded Atkins.
I think after the last few years of these kinds of things coming out, the takeaway is pretty simple: be fairly sceptical of 'advice' coming out of large governing bodies and instead just be sensible.
Don't eat too much food. Limit processed foods. Eat lots of fruit and vegetables. Eat a large variety of foods. Be active.
These rudimentary guidelines are clearly difficult for a lot of people to follow, but I think it's pretty easy to avoid negative diet effects by just doing what most people intuitively know as the right thing, even if we consume some of all types of food. It seems to me this is more about self-control and effort level than any scientific knowledge, at this point.
The more specific you get about a diet, the more specific you need to get about the person eating it. So long as most dietary advice is designed and tested at population scale, it's going to be fuzzy and inconclusive.
Even the most basic advice we can give today comes with asterisks.
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