Background: Regular consumption of fiber-rich foods is associated with reduced risk of chronic disease. Previous studies show that soluble fiber supplementation reduces fasting glucose and insulin levels by enhancing metabolism and promoting weight loss for overweight adults. The impact of dietary fiber on insulin is not fully understood in adolescents. Diet composition and nutrient metabolism are known to differ by sex.
Objective: To evaluate the association between dietary fiber intake and serum insulin levels among overweight adolescents.
Design/Methods: This is a retrospective cohort study using National Health and Nutrition Examination Surveys (NHANES) from 2003 to 2018. Inclusion criteria were ages 12-18 years with BMI ≥ 85th percentile for the respective age and sex. Subjects were excluded if missing any data on age, sex, BMI, dietary fiber, or serum insulin. Fiber intake was categorized as low (< subject age+5 g) or normal (≥ subject age+5 g) and insulin as high (≥17 uU/mL) or normal (<17 uU/mL). Student's t-tests and Chi-squared tests were used to compare demographic characteristics between male and females. Weighted Pearson's Chi-squared tests with Yates' continuity correction were conducted to test the bivariate relationships between fiber intake and serum insulin levels separately in males and females.
Results: 1597 subjects met criteria and univariate analyses showed significant differences in BMI and dietary fiber intake between females and males (Table 1). While the majority of subjects had low fiber intake, this characteristic was significantly more common in females. In females, low fiber intake was associated with high serum insulin, while normal fiber intake was associated with normal serum insulin (Table 2). In males, the relationship was the opposite-low fiber intake was associated with normal serum insulin, while normal fiber intake was associated with high serum insulin (Table 2).
Conclusions: There was a negative association for females between dietary fiber and serum insulin levels and a positive association for males. This difference may be related to differing compositions and metabolism of fiber sources in the diets of females and males. These findings inform future investigations of dietary fiber intake and its influence on insulin in overweight adolescents.
