Comparison of a Technology-based System and an In-person Behavioral Weight Loss Intervention in the Severely Obese

Inclusion Criteria: * 21-55 years of age * Body mass index (BMI) between 35.0-45.0 kg/m2 Exclusion Criteria: * Reports not having access to a computer, access to the Internet, or the availability to download software onto a computer. * Reports not having a smart phone device that is compatible with the BodyMedia® FIT Bluetooth® System that will be examined in this study. * Has a physical limitation that would prevent engaging in physical activity. * Participates in structured aerobic exercise for ≥ 60 minutes per week over the prior ≥ 3 months. * Reports being treated for a current medical condition that could affect body weight. These may include the following: cancer; diabetes mellitus; hyperthyroidism; inadequately controlled hypothyroidism; chronic renal insufficiency; chronic liver disease; gastrointestinal disorders including ulcerative colitis, Crohn's disease, or malabsorption syndromes, etc. * Reports current congestive heart failure, angina, uncontrolled arrhythmia, symptoms indicative of increase risk of an acute cardiovascular event, coronary artery bypass grafting or angioplasty, prior myocardial infarction, and conditions requiring anticoagulation therapy (i.e. deep vein thrombosis). * Has a resting systolic blood pressure ≥ 150 mmHg or resting diastolic blood pressure of ≥ 100 mmHg or taking medications to control blood pressure. * Being treated for any psychological issues (i.e., depression, bipolar disorder, etc) or taking psychotropic medications within the previous 12 months. * Taking prescription or over-the-counter medications that affect body weight and metabolism. * Has lost \> 5% of current body weight in the past 3 months and maintained this weight loss at the time of recruitment for this study. * Currently participating in an exercise or weight control study, had participated in an exercise or weight control study within the previous 6 months, or a current participant in a commercial weight reduction program. * Has undergone bariatric surgery (e.g., gastric bypass, lap-band) for weight loss. * Currently being treated for an eating disorder. * Currently pregnant, pregnant in the last 6 months, breast feeding in the last 3 months, lactating, to planning on becoming pregnant in the next 3 months. * Planning on relocating outside of the greater Pittsburgh area within the next 6 months.