I've seen/noticed this simply from being on a low carb (aka KETO) diet.

Besides AI grossly over/under estimating values even when you give it a photo of the packaging with nutritional table and tell it weight you used.

The other thing that surprised me, at least until I read up on how LLMs are actually working. Was how it would confidently BS you for your daily total.

Even when the chat/messages are just "Ate ABC with XYZ values, what's my daily total?"

While I guess new chat for each day, or some MCP for storing and retrieval of record/meals would've helped with those daily totals.

The total would still be wrong - unless you explicitly specified each of the values you need to track (e.g. carbs, fat, protein, kcal) to be put into records.

At which point of course - you're not really using AI/LLM but basically an CRUD application.