It is well known that the United States is facing an obesity epidemic and the long-term sequela are costly. Researchers continue the search for effective weight loss interventions that can be applied in outpatient settings but these are often time consuming and resource intensive, requiring repeated counseling . It is no surprise that primary care providers often omit discussing weight loss with obese patients and rarely spend adequate time on counseling. Smartphone applications (apps) may provide an alternative to resource intensive weight loss programs. In December 2013, a Pew survey found that 58% of Americans own smartphones and ownership is increasing among every demographic group including low-income populations . The nascent field of mobile health (mHealth) is rapidly expanding with experts estimating as many as 40,000 health related apps available in 2012, comprising a $718 million industry . Many of these apps aim to help individuals change behaviors to improve health, including weight loss, yet exceedingly few have been rigorously evaluated. An effective app for reducing weight could produce tremendous cost-savings by preventing long-term complications such as diabetes and cardiovascular events. To our knowledge, however, no studies have examined the effectiveness of delivering or “prescribing” an app for weight loss to patients in a clinical setting.