Body weight is a key concern in contemporary society, with large proportions of the population attempting to control their weight. However, losing weight and maintaining weight loss is notoriously difficult, and new strategies for weight loss attract significant interest. Writing about experiences of weight loss in online journals, or blogging, has recently expanded rapidly. Weight-loss bloggers typically write about daily successes and failures, report calorie consumption and exercise output, and post photographs of their changing bodies. Many bloggers openly court the surveillance of blog readers as a motivation for accountability to their weight-loss goals. Drawing from a sample of weight-loss blogs authored by women, we explore three issues arising from this practice of disclosing a conventionally private activity within an online public domain. First, we examine motivations for blogging, focusing on accountability. Secondly, we consider the online construction of self, exploring how weight-loss bloggers negotiate discourses around fatness, and rework selves as their bodies transform. Finally, we consider the communities of interest that form around weight-loss blogs. This ‘blogosphere’ provides mutual support for weight loss. However, participating in online social spaces is complicated and bloggers must carefully manage issues of privacy and disclosure.