Aria Air does not measure body fat. I'm not sure, but thinking it does not display BMI either. You might see body fat & BMI faintly on the scale display, seemingly implying they should show, but I suspect that is just using a "canned" readily available part for the display. You can see BMI on the app, though it changes quite slowly.
Best AnswerWhat makes it a smart scale then? Too much hype.