The consumption of prebiotics (fermentable and nondigestible carbohydrates) has been proposed as a potentially protective factor against overweight and obesity. However, to our knowledge, no previous prospective studies have assessed the association between the consumption of prebiotics and the incidence of overweight or obesity.We evaluated the association between prebiotic consumption [fructans and galacto-oligosaccharides (GOSs)] and the incidence of overweight [body mass index (BMI; in kg/m(2)) ≥25] in the SUN (Seguimiento Universidad de Navarra) Project, which is a prospective cohort of Spanish, middle-aged university graduates with initial BMI <25.The SUN Project is a dynamic, prospective, multipurpose cohort of Spanish university graduates with an overall retention rate of 90%. The study population encompassed 8569 Spanish university graduates (mean age: 37 y) who were initially free of overweight or obesity. Self-reported weight (previously validated) was collected at baseline and updated every 2 y during the follow-up period. Fructan consumption and GOS consumption were assessed with the use of a validated semiquantitative 136-item food-frequency questionnaire and were updated after 10 y. Time-dependent Cox proportional hazards models were used to estimate HRs and 95% CIs for incident overweight and to adjust for potential confounding factors.During follow-up (median: 9 y), 1964 incident cases of overweight were identified. After potential confounders were adjusted for, risk of overweight was 15% lower in participants in the highest quartile of fructan consumption (≥2.3 g/d) (95% CI: 0.74, 0.97; P-trend = 0.019). Subjects in the highest quartile of GOS consumption (≥0.45 g/d) had 17% lower risk of overweight (95% CI: 0.74, 0.94; P-trend = 0.001).Higher prebiotic consumption was associated with lower risk of overweight in a cohort of initially normal-weight, middle-aged adults. This potential protection has been previously scarcely assessed; therefore, additional longitudinal studies are needed to confirm our results.