OBJECTIVES: To investigate whether dietary glycaemic index (GI) and glycaemic load (GL) were associated with subsequent weight and waist circumference change. DESIGN: Population-based prospective cohort study. SETTING: Five European countries, which are Denmark, Germany, Italy, The Netherlands and the United Kingdom. PARTICIPANTS: A total of 89,432 participants, aged 20-78 years (mean =53 years) at baseline and followed for 1.9-12.5 years (mean=6.5 years). All participants were free of self-reported cancer, cardiovascular diseases and diabetes at baseline. METHODS: Glycaemic index and GL were calculated on the basis of dietary intake assessed by food frequency questionnaires and by using a GI table developed for this study with published GI values as the main sources. Anthropometric data were collected both at baseline and at the end of follow-up. Multiple linear regression analyses were conducted in each centre and random-effect meta-analyses were used to combine the effects. Adjustment was made for baseline anthropometrics, demographic and lifestyle factors, follow-up duration and other dietary factors. RESULTS: Mean GI and GL were 57 and 134, respectively. Associations of GI and GL with subsequent changes of weight and waist circumference were heterogeneous across centres. Overall, with every 10-unit higher in GI, weight increased by 34 g per year (95% confidence interval (CI): -47, 115) and waist circumference increased by 0.19 cm per year (95% CI: 0.11, 0.27). With every 50-unit higher in GL, weight increased by 10 g per year (95% CI: -65, 85) and waist circumference increased by 0.06 cm per year (95% CI: -0.01, 0.13). CONCLUSIONS: Our findings do not support an effect of GI or GL on weight change. The positively significant association between GI, not GL, and subsequent gain in waist circumference may imply a beneficial role of lower GI diets in the prevention of abdominal obesity. However, further studies are needed to confirm this finding given the small effect observed in this study.