1. A system to provide feedback for an individual's weight-loss goal, said system comprising: a. a wearable sensor device for detecting data; and b. a processing unit in electronic communication with said sensor device, said processing unit configured to accomplish the following steps, thus providing said feedback: (i) derive physiological and contextual data of the individual from data detected by said sensor device; (ii) prompt said individual to establish a weight-loss goal; (iii) generate a first suggestion to engage in an activity to assist said individual to achieve said weight-loss goal; (iv) determine weight-loss; (v) generate a second suggestion to engage in an activity to assist said individual to achieve said weight-loss goal if said weight-loss goal is not progressing toward the goal; wherein said second suggestion is based upon a determination of whether or not the individual complied with said first suggestion; and wherein said determination of whether or not the individual complied with said first suggestion is based on said derived physiological and contextual data of the individual.