Personalized Nutrition: Fad or Future?

Companies like ZOE (UK) and Viome (US) now offer diets based on your gut microbiome, glucose response, and genetics. A friend who used ZOE found better sugar control and energy but the kits cost $300+ and aren’t FDA regulated.
Are these services scientifically strong or just wellness marketing?
They show promise, but large scale clinical validation is missing.
Would you trust a diet plan made from your poop sample and genome? Where should we draw the line between wellness and evidence-based medicine?