What does an AI coach need to remember to be useful? Your goal, your current plan, your recent progress, the days you missed, and what has already been changed. Without that memory layer, advice is generated in isolation and cannot tell whether it contradicts what was recommended last week.
What is the difference between a fitness chatbot and a coaching system? A chatbot handles the answer layer. A coaching system handles the follow-through layer: workouts that know what the food guidance is supporting, food guidance that changes when training changes, and progress that influences the next decision rather than only producing a recap.
Is AI fitness advice unreliable? Not usually at the level of individual answers, which are often reasonable. The failure is structural: disconnected answers over several weeks do not add up to a coherent plan, and nothing in the exchange notices when they stop fitting together.