Techniques are described that allow an implantable device to sense gastric data and activity data from a patient, and estimate the patient's amount of energy consumed and energy expended based on the sensed data. A system provides feedback to the patient, a family member, or a doctor about the patient's energy consumed, energy expended, and net energy. The data may be provided in table or graphical format, and may show daily or weekly energy balance data or may show a trend of the daily or weekly energy data. The patient may receive feedback by an implanted alert module that provides and audio alert or a vibration alert. In addition, data acquired by the system may be used to adjust the patient's stimulation therapy parameters.