Lowering the glycemic index (GI) and glycemic load (GL) as a strategy to prevent weight gain, enable weight maintenance, and/or promote weight loss is a subject in the popular and scientific literature. Proponents both for and against such a dietary strategy can produce data from the scientific literature that support either position. This narrative review focuses on the role of GI or GL and weight and emanates from the white paper completed for the Wheat Foods Council. In addition, for the series in this publication, findings from relevant papers published since the completion of the white paper were added to the review. Overall, the findings are mixed. Studies in the aggregate fail to show a clear conclusion regarding the efficacy of adopting a low-GI or low-GL strategy for prevention of obesity or for any other aspect of weight control. Large cohort studies actually show that those whose diets are highest in GL tend to have lower body mass indexes. Intervention studies do not show an advantage of a low-GI or -GL diet for weight loss when calories are controlled. The impact of GI and GL on waist circumference, satiety, and hormones or other measures appears to be dependent on the characteristics of the participant, such as age and gender. Differences in diet composition to achieve lower GI or GL also impact outcomes. One large, recent study suggests that changes in GI alone may not matter, but that the interaction of high dietary protein and low-GI diets may help with prevent weight gain in children and aid weight loss and maintenance in adults, but more research is needed.