I tried the vegetarian diet and concluded it was not for me, by assuming it was doing without meat causing the problem, and thinking l could not absorb vegetable protein as well, but now, having adopted the whole food plant based, no sugar salt or oil, see that l was mistaken and it was because l had increased dairy and that was a major problem for me.
This is a problem for many l think, making such assumptions because they are not basing their choice on research and the plant based diet has more of that, and going on for longer, than any other diet. It is proven to reverse heart disease and no other diet has that record.
If you cover the few possible deficiencies which will always include b12 your body will be your guide and will clearly show you what not to eat, and after having tried just about every diet known l have found that no other diet can be relied on in this way.
You do not have to spend acres of time studying nutrition, you only have to listen to the top plant based doctors on YouTube, who will cite the research they use including the China Study, and basically just see for yourselves how they look in their old age. I dont see any keto fans in their old age.
Low carbing nearly destroyed my health despite eating masses of leafy greens as it increased insulin resistance and gave me gall bladder and pancreas attacks.