Background: Arguments supporting the involvement of users in research have even more weight when involving the public in systematic reviews of research. We aimed to explore the potential for public involvement in systematic reviews of observational and qualitative studies. Methods: Two consultative workshops were carried out with a group of young people (YP) aged 12-17 years to examine two ongoing reviews about obesity: one about children's views and one on the link between obesity and educational attainment. YP were invited to comment on the credibility of themes, to propose elements of interventions, to suggest links between educational attainment and obesity and to comment on their plausibility. Results: Researchers had more confidence in review findings, after checking that themes identified as important by YP were emphasised appropriately. Researchers were able to use factors linking obesity and attainment identified as important by YP to identify limitations in the scope of extant research. Conclusion: Consultative workshops helped researchers draw on the perspectives of YP when interpreting and reflecting upon two systematic reviews. Involving users in judging synthesis credibility and identifying concepts was easier than involving them in interpreting findings. Involvement activities for reviews should be designed with review stage, purpose and group in mind.