Dietary carbohydrate quantity and quality in relation to obesity: A pooled analysis of three Finnish population-based studies

Background: The relationship between carbohydrate intake, dietary glycaemic index (GI) and load (GL), and obesity remains unsolved. Sugar intake and obesity represent a timely topic, but studies on sugar subcategories are scarce. We aimed to study whether total carbohydrate, sucrose, lactose, fibre, dietary GI, and GL are associated with obesity in 25–79-year-old Finns. Methods: Our pooled analysis included three cross-sectional population-based studies: the DILGOM Study (n = 4842), the Helsinki Birth Cohort Study (n =1979), and the Health 2000 Survey (n = 5521). Diet was assessed by a validated food-frequency questionnaire, and anthropometric measurements were collected by standardised protocols. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated using logistic regression analysis. Results: In the model, which included sex, age, education, smoking, physical activity, and energy intake, the likelihood of being obese (body mass index ⩾ 30 kg/m2) appeared lower in the highest quartiles of total carbohydrate (OR 0.65; 95% CI 0.57–0.74; P for trend < 0.0001), sucrose (OR 0.53; 95% CI 0.47–0.61; P < 0.0001), and dietary GL (OR 0.64; 95% CI 0.56–0.73; P < 0.0001) compared to the lowest quartiles. In contrast, dietary GI did not associate with obesity. Fibre intake associated inversely with abdominal obesity (OR 0.80; 95% CI 0.71–0.90; P < 0.001). The inverse sucrose–obesity relationship appeared stronger in high fruit consumers compared to low fruit consumers (P for interaction 0.02). Conclusions: Although most of the studied carbohydrate exposures were associated with a diminished likelihood of being obese, prospective studies are needed to assess temporal relations to support causal inference.