Obesity and fat quantification in lean tissues using three-point Dixon MR imaging

Background: It has been suggested that increased hepatic and intramuscular fat is associated with insulin resistance, and that increased pancreatic fat is related to impaired insulin secretion. Objective: We postulated that in obese nondiabetic teenagers insulin levels would be directly related to increases in intramuscular and hepatic fat and inversely related to increases in pancreatic fat. Materials and methods: MRI was used to assess the percentage of fat in the liver, muscle and pancreas in 15 healthy Mexican-American girls, 14–17 years old, with body mass indexes (BMIs) ranging from 17.7 kg/m² to 46 kg/m². Results: Strong correlations were observed between BMI and fat content in the liver, muscle, and pancreas (r²s between 0.50 and 0.89; P<0.003). Serum insulin levels were closely associated with fat measures in the muscle and liver (r^2s=0.63 and 0.29, and P=0.001 and P=0.023, respectively). In contrast to our hypothesis, fat content in the pancreas was also directly related to insulin secretion (r²=0.74; P=0.001). Summary: We conclude that in nondiabetic teenagers, obesity is associated with an increased accumulation of fat in the pancreas without impairment of insulin secretion.