While I agree with the larger sentiment, there is a rather substantial amount of diet and nutrition science with the core being quite an agreed upon set of foundational principles.
If I were to summarize:
1. We derive energy from three major macronutrients (protein, fat and carbohydrates)
2. Our body has certain macronutrients it cannot synthesize and NEEDS for healthy functioning (essential fatty acids and essential amino acids)
3. Our bodies are largely energy efficient (by which I mean the processes to produce energy are readily actionable with average hormone levels of insulin/ghrelin/leptin etc.) when consuming carbohydrates, but can turn to other nutrient sources when they are not to be found.
4. Our body composition can be manipulated by manipulating our energy expenditure either via manipulating the caloric content of food or via the preferential production of body tissue from horomonal influence (this is why muscle mass increases when using testosterone even if caloric intake is kept constant but above a certain macronutrient threshold).
5.There are a certain set of micronutrients we need on a continuous basis (the exact amounts of which are up for debate but the ranges seem to be reasonably agreed upon).
6. Our diet influences our gut fauna and this further influences how much nutritional value we get from our diet, it is quite a symbiotic cycle.
7. Barring certain specific horomonal imbalance diseases, everyone's body largely abides by the above principles, (i.e as special as everyone thinks they are, they're probably more average than not when it comes their metabolism).
> On 3. note that carbohydrates are the only of the three macronutient we don't need to eat at all (see eskimo).
This isn't true. Although the Intuit people were largely carnivorous, they did not have a "keto" diet. They ate a lot of meat, but the animals they ate have extremely high amounts of natural glycogen. They also did not eat as much fat as expected, because animal fat was their source of heat and light for long winter nights.
> ...When is abundant, the average daily diet of the adult Eskimo consists approximately of 30 to 40 grams of carbohydrate (which includes glycogen), 250 to 300 grams of protein, and about 150 grams of fat (FA/G=1.2). These amounts of meat are apparently not heroic, for it has been alleged that the Yakuts, on the Low Steppe, east of the Lena, eat as much as 25 and 30 pounds of meat a day.”
—I.M. Rabinowitch (1936)
If you are curious, this is an accessible review of the available materials.[1]
I think when walking on the street of place like US (or UK, Australia etc.) its pretty damn obvious that many folks didn't accept that 'earth is round' in nutrition world, based on their weight and self-inflicted diseases stemming from it.
I'd say globally we can add on average 10 years of good quality life to every single person if they understood the points above and acted accordingly.
This and some form of healthy regular exercise and one is basically maximizing his lifespan in best currently available way. Increased happiness level is just a nice by-product.
If I were to summarize:
1. We derive energy from three major macronutrients (protein, fat and carbohydrates)
2. Our body has certain macronutrients it cannot synthesize and NEEDS for healthy functioning (essential fatty acids and essential amino acids)
3. Our bodies are largely energy efficient (by which I mean the processes to produce energy are readily actionable with average hormone levels of insulin/ghrelin/leptin etc.) when consuming carbohydrates, but can turn to other nutrient sources when they are not to be found.
4. Our body composition can be manipulated by manipulating our energy expenditure either via manipulating the caloric content of food or via the preferential production of body tissue from horomonal influence (this is why muscle mass increases when using testosterone even if caloric intake is kept constant but above a certain macronutrient threshold).
5.There are a certain set of micronutrients we need on a continuous basis (the exact amounts of which are up for debate but the ranges seem to be reasonably agreed upon).
6. Our diet influences our gut fauna and this further influences how much nutritional value we get from our diet, it is quite a symbiotic cycle.
7. Barring certain specific horomonal imbalance diseases, everyone's body largely abides by the above principles, (i.e as special as everyone thinks they are, they're probably more average than not when it comes their metabolism).