BackgroundMobile phone short message service (SMS) text messaging, has the potential to serve as an intervention medium to promote sustainability of weight loss that can be easily and affordably used by clinicians and consumers.ObjectiveTo develop theoretically driven weight loss sustaining text messages and pilot an mHealth SMS text messaging intervention to promote sustaining recent weight loss in order to understand optimal frequency and timing of message delivery, and for feasibility and usability testing. Results from the pilot study were used to design and construct a patient privacy compliant automated SMS application to deliver weight loss sustaining messages.MethodsWe first conducted a pilot study in which participants (N=16) received a daily SMS text message for one month following a structured weight loss program. Messages were developed from diet and exercise guidelines. Following the intervention, interviews were conducted and self-reported weight was collected via SMS text messaging.ResultsAll participants (N=16) were capable of sending and receiving SMS text messages. During the phone interview at 1 month post-baseline and at 3 months post-baseline, 13/14 (93%) of participants who completed the study reported their weight via SMS. At 3 months post-baseline, 79% (11/14) participants sustained or continued to lose weight. Participants (13/14, 93%) were favorable toward the messages and the majority (10/14, 71%) felt they were useful in helping them sustain weight loss. All 14 participants who completed the interview thought SMS was a favorable communication medium and was useful to receive short relevant messages promptly and directly. All participants read the messages when they knew they arrived and most (11/14, 79%) read the messages at the time of delivery. All participants felt that at least one daily message is needed to sustain weight loss behaviors and that they should be delivered in the morning. Results were then used to develop the SMS text messaging application.ConclusionsStudy results demonstrated the feasibility of developing weight loss SMS text messages, and the development of an mHealth SMS text messaging application. SMS text messaging was perceived as an appropriate and accepted tool to deliver health promotion content.