One key problem is it’s not a simple rule like x diet is “best”, or even x diet is “good.” Instead it depends on what are you trying to accomplish – best for losing weight (and keeping it off)? best for athletic performance or general day to day functioning? best for longevity? best to support your unique medical conditions such as insulin sensitivity or genetic cardiovascular risk? best to get adequate nutrition while maintaining a low calories? … Many of these goals are also going to depend on the individual. For example, the most effective diet for losing weight may be completely different for different persons. This can be a limitation for apps like Yuka that give a simple number that is not associated with for your particular goals.
However, there are some basic recommendations that are not constantly shifting such as eating lots of fruits and vegetables; eating a combination of foods that supports adequate protein, fiber, vitamins, minerals, EFAs…; limiting/avoiding processed foods, particularly highly processed foods; etc.
A huge variety of diets that meet these basic recommendations may work well for different people in different situations. For example, the relatively small population of Tarahumara Indians in Mexico became will known for their performance in endurance events, such as 100+ mile runs. When they started showing up at US endurance events in the 90s, they appeared to be doing everything wrong… no stretching or warming up, wearing sandals, smoking… yet a 55-year-old Tarahumara farmer set a course record in the Leadville 100 by a large margin, with 3 of the top 4 being Tarahumaras; shortly followed by Tarahumaras getting 3 of top 10 in the 95 Western States 100 (one of the biggest and most challenging ultramarathon events in US). Their traditional diet is ~80% carbs / 10% protein / 10% fat. That traditional diet has worked very well for the tribe with low rates of cardiovascular disease, cancer, diabetes, being overweight… in addition to their performance in endurance sports. One study writes,
“Particularly notable was the virtual absence of the hypertension, obesity, and the usual age rise of the serum cholesterol in adults. Thus, the customary diet of the Tarahumaras is adequate in all nutrients, is hypolipidemic, and is presumably antiatherogenic.”
It’s only after their diet became more Americanized in recent decades that negative health effects became more common.
At the other extreme, the traditional Innuit diet is ~50% fat / 30% protein / 20% carbs. They also had relatively low rates of most of the common diseases associated with diet… or at least lower than Americans.
I could list many more examples of different diets that seem to work well for different populations – " Mediterranean? Low carb? High protein?.." they all may work well for different people in different situations. However, one diet that does not work well is the common American diet, that gets the bulk of calories from ultra-processed foods and few calories from natural, unprocessed foods.
