I personally think that the recommendations are healthy and are what is best for the majority of healthy people who want to stay healthy. Because that is what the recommendations are for. If someone is at an extreme, either too low weight or too high weight, or has an illness then the recommendations are of course different, and that is what people need to remember. But also that the recommendations are set a "group level" and not an individual level. So every individual can adjust the recommendations based on how their body works or their lifestyle and such. For example some find that they function best with a lower colohydrate intake and more fats, while others are the opposite and find that they function better with more colohydrates and less fat. And that is inidividual, the recommendations arent saying that everyone should eat like this. But what i do like about the recommendations is that they encourage all the food groups, that a food group shouldnt be eliminated or severly restricted... but that all the macronutrients are needed for optimal health and thats what everyone should realise.
With studies, i havent read so many of the studies but what i know is that the recommendations and everything written about the recommendations is based on study and research, and unbiased research as far as i am aware. (Of course, correct me if i am wrong). But many diets or fad diets that come around, their "research" is biased and created in a way that they get the results they wanted... they arent fair studies. And if a study doesnt give them the results they wanted they have 5 others they can use. But also... many diets claim that their way works, and why it works is because people do it for a short term and restrict alot and lose weight.... thats why all the diets work, because their is a decrease in calories. But if a person finds a balance and learns lifestyle types, such as lets take the LCHF diet which is an extreme diet mostly and there is research behind it, but i wouldnt trust the research because there is lots of research and studies going against them, which says why too much fat is bad for the body. But for example, if someone starts the LCHF diet and learns healthier tips and habits, they might not be so strict, they still eat a moderate amount of carbs and enough protein and not too high fat and they change their lifestyle... then the "diet" works long term when all they really did was change their habits. But then if someone goes strict on the LCHF diet, loses lots of weight and doesnt change their lifestyle then the results wont last and the "Health benefits" they get was just because of the decrease in calories compared to before (i.e an overweight person who eats far too much each day, then decreases to the right amount they should eat... that will help their body and those results will show if they do tests), and if those results are taken into studies it shows that "positive results were shown" but it wont say anymore about whether the person regained weight afterwards etc etc
Back to the main question...... the recommendations are based on studies, however the studies are oftne done on people who have problems or have the capacity to show change. For example if you take 50 people with high blood pressure and you put them on a diet with less sodium and less sugar, then after a few weeks their blood pressure will have decreased and maybe decreased even more after another few weeks, and then they write that less sodium is a recommendation. The studies arent done on fully healthy people, because there isnt so much to change... if a person has a healthy fat percent or a normal blood pressure or heart rate, then they shouldnt exactly lower it.
So my teacher told us, that if someone is healthy then they can keep doing what they are doing. The recommendations are just that...recommendations but also about helping people make lifestyle changes and about staying healthy.
Long answer, hahaha... but when i am studying things like this i could write lots about it :)
And then. Have you ever thought about getting paid for blogging?