Prevalence and Clinical Characteristics of Children and Adolescents with Metabolically Healthy Obesity: Role of Insulin Sensitivity

Abstract

Obesity represents a major risk factor for metabolic disorders, but some individuals, "metabolically healthy" (MHO), show less clinical evidence of these complications, in contrast to "metabolically unhealthy" (MUO) individuals. The aim of this cross-sectional study is to assess the prevalence of the MHO phenotype in a cohort of 246 overweight/obese Italian children and adolescents, and to evaluate their characteristics and the role of insulin resistance. Homeostasis model assessment-insulin resistance (HOMA-IR), insulin sensitivity index (ISI), insulinogenic index (IGI) and disposition index (DI) were all calculated from the Oral Glucose Tolerance Test (OGTT). MHO was defined by either: (1) HOMA-IR < 2.5 (MHO-IRes), or (2) absence of the criteria for metabolic syndrome (MHO-MetS). The MHO prevalence, according to MHO-MetS or MHO-IRes criteria, was 37.4% and 15.8%, respectively. ISI was the strongest predictor of the MHO phenotype, independently associated with both MHO-IRes and MHO-MetS. The MHO-MetS group was further subdivided into insulin sensitive or insulin resistant on the basis of HOMA-IR (either < or ≥ 2.5). Insulin sensitive MHO-MetS patients had a better metabolic profile compared to both insulin resistant MHO-MetS and MUO-MetS individuals. These data underscore the relevance of insulin sensitivity to identifying, among young individuals with overweight/obesity, the ones who have a more favorable metabolic phenotype.

Keywords: adolescents; children; insulin resistance; metabolic syndrome; metabolically healthy obesity.

Figure 1

Plasma glucose and insulin levels during OGTT in MHO-IRes vs. MUO-IRes (A). Plasma glucose and insulin levels (B) and OGTT-derived indices (C) in insulin sensitive MHO-MetS, insulin resistant MHO-MetS and MUO-MetS subjects. * Indicates significant differences.

Figure 2

Prevalence of the MHO condition. In our cohort of subjects, 37.4% had none of the criteria of metabolic syndrome (MHO-MetS), and 15.8% were classified as MHO on the basis of the absence of insulin resistance (HOMA-IR < 2.5, MHO-IRes). The blue area of the Venn diagram represents MHO-MetS having HOMA-IR ≥ 2.5 (insulin resistant MHO-MetS). The overlap of the two definitions (the green area) identifies the sub-cohort of MHO-MetS with HOMA-IR < 2.5 (insulin sensitive MHO-MetS).