Most young adults gain weight while attending college, setting the stage for long-term weight gain, and associated chronic disease. Interventions that use social and mobile technologies, and leverage social network support may help students adopt health-enhancing habits such as regular exercise. The first study explored how overweight/obese college students participa-ting in project SMART (N=404), a remotely delivered 2-year weightloss trial, engaged their social networks, and used social and mobile technologies xxiii while trying to lose weight. The second study tested whether participants in the treatment (versus control) group talked more about diet and exercise with their Facebook friends, and the third study tested whether this type of online communication, and receiving social support for it was associated with weight loss. Study One involved qualitative interviews with a convenience sample of participants (n=38), intercepted after one of their measurement visits. Study Two involved building a dictionary of diet and exercise words that was used to classify participants' Facebook posts as being about HAL or not. Study Three quantified the number of likes and comments on posts (i.e., social support), and tested whether posting about HAL or receiving social support for HAL was associated with weight loss. Study One found that participants in the control and treatment groups used non-study designed apps to help them lose weight and many participants knew one another. Individuals talked about their weight-loss goals with friends and felt accountable to follow through with their intentions. Study Two found that treatment group participants posted more HAL than those in the control from baseline to +6 months of participation (Beta=1.75; p<0.05) but this effect did not persist over time. Study Three found no association between HAL posts and weight loss but the association between social support for HAL posts and weight loss (kg) approached significance at +18 months of participation (Beta= -0.20; p=0.07). xxiv Interventions using social and mobile technologies should measure participants' direct-to-consumer technology use and interconnectivity so that treatment effects can be isolated and cross-contamination accounted for. Future work will test how social network connections, and network structure is associated with weight loss among this population.