Sometimes I think "fitness gurus" overstate the importance of the gut microbiome, but this is one area of research that is really in its very early stages.
It does make sense that what you eat will influence the makeup of your gut microbiome, and based on what I know about microbiology, it stands to reason that you would want a diverse population of bacteria in your gut. If all you eat is protein and fat, then that's likely going to push out bacteria that utilize carbs, sugars, and fiber.
That in turn is going to make it more difficult for your body to process fibrous veggies - and you will further exclude that food group from your diet.
There are a lot of studies that demonstrate the benefits of fiber, so I personally feel like that could be one negative effect of diets like carnivore.
It does make sense that what you eat will influence the makeup of your gut microbiome, and based on what I know about microbiology, it stands to reason that you would want a diverse population of bacteria in your gut. If all you eat is protein and fat, then that's likely going to push out bacteria that utilize carbs, sugars, and fiber.
That in turn is going to make it more difficult for your body to process fibrous veggies - and you will further exclude that food group from your diet.
There are a lot of studies that demonstrate the benefits of fiber, so I personally feel like that could be one negative effect of diets like carnivore.