I don't know why people are using AI to meal track and count calories. MyFitnessPal is dumb easy to use already, and it has, by far, the most robust nutrition facts database out there (they've been in the same for 20 years now; I've been using it since 2008.)

Any nutrition facts these models might use are vectoring either to data from this database or FatSecret. Anything custom, like estimating meals at most restaurants, is going to involve adding and multiplying stuff, and we know how great LLMs are at that.