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/m(2)) 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.