Standard behavioral treatment (SBT) for obesity is often effective, but weight losses are highly variable, and patients sometimes fail to achieve a "successful" weight loss of 5-10% of their starting weight. It has been suggested that the "one size fits all" approach of SBT may be responsible for many treatment failures because the intervention is not sufficiently tailored to address the unique needs of each patient. Moreover, treatment is delivered in the clinic, not in the settings and the times when it is needed most. The primary aim of the proposed research is to develop and pilot test a behavioral weight loss intervention that combines in-person sessions with treatment delivered via an electronic handheld device to provide highly individualized weight loss treatment in patients' natural environment. In a critical departure from previous research using cell phone technology, the portion of intervention that is delivered via handheld device will be of equal sophistication and importance to the portion of the intervention that is delivered in face-to-face treatment sessions. The proposed study seeks to determine the feasibility and preliminary efficacy of an individually tailored behavioral weight loss program that integrates clinic-based care and smartphone technology.

Inclusion Criteria:

• Body Mass Index (kg/m2) of 30-45.
• English language fluency
• Basic familiarity with cell phone technology
• Ability to read at a 6th grade level
• Availability to attend weekly treatment sessions in Providence, RI

Exclusion Criteria:

• Any heart condition that limits ability to participate in physical activity
• Chest Pain
• Any cognitive of physical limitation that would preclude use of a smartphone
• Serious mental illness
• Historical or current eating disorder
• Previous or planned bariatric surgery
• Use of weight loss medication
• Recent pregnancy or a plan to become pregnant in the next 6 months
• Participation in a study at the Weight Control and Diabetes Research Center within the last two years
• A weight loss of greater than 5% body weight in the last 6 months