I was on a keto diet — a low-carb high-fat diet — for several years, but I switched to a whole-food (no refined foods or “product foods”) plant-based (no food from animal sources) with very good results wrt weight loss, control of blood glucose (without medication), and so on.

The problem with a keto diet is that such a diet in general is very low in dietary fiber, and dietary fiber is what nourishes the gut microbiome. I do understand that in a keto/low-carb diet one limits net carbs (total carbs minus dietary fiber), so in theory one could maintain a good intake of dietary fiber, but in practice I believe that the keto diet will not provide even the minimum recommended intake of dietary fiber. In the US, the percentage of men age 18–50 who consume even the minimum recommend daily intake of dietary fiber is 0%. Zero.

I will point out that the statements regarding the plant-based diet are supported by research, some of which is cited in the footnotes.