Purpose: Worldwide, the number of obese persons continues to grow. Online-mediated self-help groups represent an opportunity for obese persons to support each other. The aim of our study was to evaluate whether and how the use of and active participation in online self-help groups is associated with perceived informational and emotional support among obese adults. Methods: We conducted an online-based questionnaire (N= 230) with users of online self-help groups for obese adults in Germany. Results: Findings revealed that forum activity is significantly correlated with perceived informational and emotional support. While asking questions was strongly correlated with both types of social support, sharing opinions and answering posts were more strongly correlated with perceived emotional support. Conclusion: The level of social support in online communities depends on an individual's forum activity. Our findings offer a foundation for professionals in the health care sector to enhance their understanding, make recommendations, and further develop online self-help groups. (C) 2017 Elsevier B.V. All rights reserved.