A low visceral fat proportion, independent of total body fat mass, protects obese adolescent girls against fatty liver and glucose dysregulation: a longitudinal study.

ABSTRACT

BACKGROUND: The relative proportion of visceral fat (VAT) to subcutaneous fat (SAT) has been described as a major determinant of insulin resistance (IR). Our study sought to evaluate the effect of body fat distribution on glucose metabolism and intrahepatic fat content over time in a multiethnic cohort of obese adolescents. SUBJECTS/METHODS: We examined markers of glucose metabolism by oral glucose tolerance test, and body fat distribution by abdominal MRI at baseline and after 19.2 ± 11.4 months in a cohort of 151 obese adolescents (88 girls, 63 boys; mean age 13.3 ± 3.4 years; mean BMI z-score 2.15 ± 0.70). Hepatic fat content was assessed by fast-gradient MRI in a subset of 93 subjects. We used the median value of VAT/(VAT + SAT) ratio within each gender at baseline to stratify our sample into high and low ratio groups (median value 0.0972 in girls and 0.118 in boys). RESULTS: Female subjects tended to remain in their VAT/(VAT + SAT) category over time (change over follow-up P = 0.14 among girls, and P = 0.04 among boys). Baseline VAT/(VAT + SAT) strongly predicted the hepatic fat content, fasting insulin, 2-h glucose, and whole-body insulin sensitivity index at follow-up among girls, but not in boys. CONCLUSIONS: The VAT/(VAT + SAT) ratio is a major determinant of impaired glucose metabolism and hepatic fat accumulation over time, and its effects are more pronounced in girls than in boys.