Impaired glucose tolerance in healthy men with low body weight

Background: Impaired glucose tolerance (IGT) and high body mass index (BMI) are recognized risk factors for type 2 diabetes mellitus (T2DM). However, data suggest that also underweight predisposes people to develop T2DM. Here, we experimentally tested if already moderate underweight is associated with impaired glucose tolerance as compared to normal weight controls. Obese subjects were included as additional reference group. Method: We included three groups of low weight, normal weight, and obese subjects comprising 15 healthy male participants each. All participants underwent a standardized hyperinsulinemic-euglycemic glucose clamp intervention to determine glucose tolerance. In addition, insulin sensitivity index (ISI) was calculated by established equation. Results: ISI values were higher in low and normal weight than in obese subjects (P < 0.010) without any difference between low and normal weight groups (P = 0.303). Comparable to obese participants (P = 0.178), glucose tolerance was found decreased in low weight as compared with normal weight subjects (P = 0.007). Pearson's correlation analysis revealed a positive relationship between glucose tolerance and BMI in low (P = 0.043) and normal weight subjects (P = 0.021), an effect that was found inverse in obese participants (P = 0.028). Conclusion: Our study demonstrates that not only obese but also healthy people with moderate underweight display glucose intolerance. It is therefore suggested that all deviations from normal BMI may be accompanied by an increased risk of developing T2DM in later life indicating that the maintenance of body weight within the normal range has first priority in the prevention of this disease.