Nutrition studies are not very useful because generally speaking scientists can't control every aspect of a person's nutrition. With practices like fasting and rigid dietary restrictions rarely can you get a volunteer normie to change their life so significantly for a study, so all of them are so unbelievably tame like intermittent fasting only instead of 3,4,5+ day fasts. If it turned out that not consuming anything is actually great for you, no legitimate food corporation would fund its publishing lol. Also, the testing categories are very vague. Many studies list lean, organic meats in the same category as junk food and processed, canned meats. Populations react differently to different diets, consider that more than half of the world finds Lactose inflammatory despite milk products being a healthful source of proteins, calcium, Bvits and beneficial micro-organisms for a minority.
In short, the 'healthiest' foods are the most subsidized and cheapest to mass-produce at the time. However you have to be careful with so-called independent researchers too. Most of the time they're trying to sell their all-natural-organic-supplements-that-totally-work™. I'm talking about the Bergs, the Johnsons, the Gundrys. The best approach is to simply be sensible and eat a variety of whole foods. Emergent research is starting to focus more on how your diet affects the bacterial and fungal colonies that populate your body, which tweak biochemical conversion pathways, so I'm sure we'll learn in 10 years or so that simple sugars are actually great for you because they're easily converted to energy for symbiotic bacteria in the gut(!).
