Food-tracking apps constitute a major category of the thousands of food-related apps now available. They are promoted as helping users monitor and measure their food consumption to improve their health or to lose weight. In this article, I present six vignettes drawn from interviews with Australian women about their use and non-use of food-tracking apps. The vignettes provide detailed insights into the experiences of these women and their broader sociocultural and biographical contexts. The analysis is based on feminist materialism theoretical perspectives, seeking to identify the relational connections, affective forces, and agential capacities generated in and through the human-app assemblage. The vignettes reveal that affective forces related to the desire to control and manage the body and conform to norms and ideals about good health and body weight inspire people to try food-tracking apps. However, the agential capacities promised by app developers may not be generated even when people have committed hope and effort in using the app. Frustration, disappointment, the fear of becoming too controlled, and annoyance or guilt evoked by the demands of the app can be barriers to continued and successful use. Sociocultural and biographical contexts and relational connections are also central to the capacities of human-app assemblages. Women’s ambivalences about using apps as part of efforts to control their body weight are sited within their struggles to conform to accepted ideals of physical appearance but also their awareness that these struggles may be too limiting of their agency. This analysis, therefore, draws attention to what a body can and cannot do as it comes together with food tracking apps.