<qa>  How many obese participants will be randomized to a condition in which they will be ableIn a pilot randomized trial of 160 obese participants, investigators will test the feasibility of a behavioral weight loss program delivered entirely via Facebook. Participants will be randomized to a condition in which they will be able to invite their friends, or a condition with study participants only. All participants will receive behavioral counseling via the private Facebook group from the coaches who are present on the network daily. Participants will track their diet and exercise via a free commercial mobile app. 