OBJECTIVE: What happens when people see others making progress toward a goal that they also hold? Is it motivating or could it undermine goal pursuit because people feel that they have made progress themselves (i.e., they experience vicarious goal satiation)? METHODS: We investigated these questions in a longitudinal field context - a group weight loss programme. N = 132 participants who were overweight or obese and attended weekly weight loss classes completed questionnaires over 11 weeks to investigate the consequences of observing other people making progress toward their goal of losing weight RESULTS: Observing others making good progress was associated with participants holding stronger intentions to lose weight themselves (B = 0.04, p = .012), positive goal-related affect (B = 0.27, p = .017), and feeling that they were also making progress themselves (B = 0.22, p < .001). However, observing others making good progress was also associated with losing a smaller amount of weight over the following week (B = .13, p = .005). Mediation analyses showed a significant indirect effect of observing others making good progress, via feelings about their own progress, on changes in weight, B = .02, 95% CI [.00, .04]. CONCLUSIONS: People who view others making progress tend to be less successful at losing weight themselves over the following week. The findings suggest that this is, in part, explained by the person feeling as if they have made progress themselves; thereby providing the first demonstration of vicarious goal satiation in a field context. Statement of contribution What is already known on this subject? Many people strive toward health goals (e.g., try to lose weight) with other people. However, research into vicarious goal satiation (VGS) suggests that seeing someone else achieve their goal may lead people to believe that they have made progress themselves and undermine goal pursuit. What does this study add? A longitudinal test of VGS in a field context, namely weight loss groups. Observing other people do well was motivating for the observer. They also believed that they had made progress themselves and were less successful at losing weight