I do this at the moment in my hand rolled personal assistant experiment built out of Claude code agents and hooks. I describe my workouts to Claude (among other things) and they are logged to a csv table. Then it reads the recent workouts and makes recommendations on exercises when I plan my next session etc. It also helps me manage projects, todos, and time blocked schedules using a similar system. I think the calorie counter that the OP describes would be very easy to add to this sort of set up.