Amazon lists 60,000 books under the search term diet. That many books on the same subject tells me that there is no accepted standard. Different books propose different styles of eating: “Avoid carbohydrates!” “Eat intermittently!” “Eat like a caveman!” “Increase foods that are antioxidants!” The list of recommendations is vast.
Assuming that “healthy eating” refers to a diet that will allow you to avoid disease and enhance your strength and vigor, your search is in vain. Why? Because accepting existing reports of healthy eating on a similar basis to other reports on health-promoting, or unhealthy behaviors, misses an important difference. To prove the effects of any one of the numerous published “healthy eating” proposals requires information that is not available.
Let’s review how something is proved. In medicine, the gold standard is the controlled clinical trial. Here, two or more groups are stratified by some blind, randomized process into what seem like equally eligible participants. Each group gets a unique treatment: one may get one drug while one may get another or may get a placebo. When the populations are compared after a predetermined period of time, any difference between them must have been due to their specific treatment. There are no random events to confuse the conclusions.