OBJECTIVE: To evaluate the association between dietary fibre intake and obesity in Japanese outpatients with type 2 diabetes, as well as the demographic and dietary factors influencing this association. DESIGN: Cross-sectional study with nationwide registry data on Japanese type 2 diabetes outpatients (2014–2019). Diet was self-reported via a FFQ. Obesity was defined as BMI ≥ 25 kg/m SETTING: Clinics throughout Japan. PARTICIPANTS: 1565 Japanese outpatients with type 2 diabetes (63·1 % men
age range 30–89 years). RESULTS: Multivariate analysis revealed that a higher dietary fibre intake was associated with a lower risk of obesity in all participants (95 % CI = 0·439, 0·795, CONCLUSION: Higher fibre intake was associated with lower obesity risk, particularly in men and older age groups. These findings emphasise the need for targeted public health initiatives promoting the intake of diverse fibre-rich foods to effectively manage obesity. Further research is needed to understand sex- and age-specific factors in the fibre–obesity relationship in diverse populations.