Dietary fiber density as an important modifying factor in the association between rice intake and obesity in Japanese type 2 diabetes outpatients: a sex and age-stratified cross-sectional investigation (JDDM 80)

A meta-analysis of cohort studies found a positive association between white rice consumption and chronic disease risk, particularly in women. However, the association between rice intake and obesity remains inconsistent across populations. We aimed to examine the relationship between rice intake and obesity stratified by sex and age. This cross-sectional study used nationwide registry data from Japanese type 2 diabetes outpatients (2014-2019). Obesity was defined as BMI ≥25 kg/m². The study included 1,565 outpatients aged 30-89 years (mean age: 62.3 ± 11.6 years), with 63.1% being male. Rice intake was associated with a diet low in energy from protein, fiber density, and dairy products. In adjusted multivariate analysis, older women in the highest tertile of rice intake had a higher prevalence of obesity (95% CI = 1.104-4.260, p trend = 0.042); however, this association lost significance after adjusting for fiber density (95% CI = 0.864-3.558, p trend = 0.080). In younger women, an inverse association with obesity emerged after fiber density adjustment in the supplementary quartile analysis. No significant associations were found in men. These results suggest that the association between rice intake and obesity is influenced by overall dietary quality rather than rice consumption alone. Promoting greater dietary diversity while maintaining traditional staples like rice may be a practical strategy to improve diet quality in Japan. Prospective studies in Japanese and other populations are needed to confirm these associations.