The study will evaluate whether a technology-based lifestyle intervention program using primarily a smartphone platform is an acceptable and effective way for treating obesity. The goal of the program is to achieve weight loss and enhance the health of overweight or obese subjects by improving their diet and activity via smartphone applications as compared with conventional in-person weight management programs.

Inclusion Criteria:

• Overweight or obese BMI 25-42 kg/m2
• Employed in sedentary occupations
• Own a personal smartphone with unlimited data plan or >4 GigaByte data
• Proficient with use of smartphone applications and technology with current daily usage
• Ability to engage in moderate intensity exercise
• Weight stability for the last 2 months
• Participants must be willing to comply with all study-related procedures

Exclusion Criteria:

• Current or planned pregnancy
• Cardiovascular, pulmonary, renal disease, joint disease
• Uncontrolled thyroid disease
• History of eating disorders, psychiatric disease
• History of substance abuse or dependence in the last 1 year
• Diabetes
• Shift work
• Previous weight loss surgery
• Use of weight loss drugs/diet/program in the last 6 weeks
• Inability to increase walking as a form of exercise and to engage in moderate intensity exercise
• Other conditions or medications that affect body weight/appetite/metabolism
• Serious or unstable medical or psychological conditions that would compromise the subject's safety for successful participation
• Incapable of adhering with an intensive lifestyle intervention using technology and smartphone applications