200 overweight adults aged 18 to 65 years will be randomly assigned to one of four groups: (1) a standard behavior change weight loss group-based program (14 group sessions over a 4 month period followed by 6 phone calls over a 5 month period), (2) a standard behavior change weight loss group-based program (15 group session over a 4 month period followed by 6 phone calls over a 5 month period) combined with the armband, (3) the armband alone (training in the use of the armband and a follow up telephone call), or (4) a self-directed weight loss control group.