System and method to determine user compliance with personalized diet and exercise plans by analyzing responses to messages about the plans. An expert system has a number of stored messages and display characteristics from which it chooses. The expert system generates message relating to the user's diet or physical activity that are sent to a user's mobile device and analyzes responses. Display characteristics change periodically and compliance data relating to the user's adherence to the plan when certain display characteristics are used is stored (e.g., meal plan adherence, acceptance of specific food selections, and adherence to instructions and advice in messages). The expert system then determines which messages and display characteristics achieve the greatest compliance to the dietary and physical activity schedule and goals.