Definition of new cut-offs of BMI and waist circumference based on body composition and insulin resistance: differences between children, adolescents and adults

Abstract

SummaryObjectiveThis study aims to determine associations between anthropometric traits, regional fat depots and insulin resistance in children, adolescents and adults to define new cut‐offs of body mass index (BMI) or waist circumference (WC).DesignCross‐sectional data were assessed in 433 children, adolescents and adults (aged: 6–60 years, BMI: 23.6 [21.0–27.7] kg m−2). Total adipose tissue (TAT), regional subcutaneous adipose tissue (SATtotal, SATtrunk) and visceral adipose tissue (VAT) were determined by whole‐body magnetic resonance imaging, fat mass by air‐displacement plethysmography. Insulin resistance was evaluated by homeostasis model assessment of insulin resistance (HOMA‐IR). Bivariate as well as partial correlations and regression analyses were used. Cut‐off values of BMI and WC related to regional fat depots and HOMA‐IR were analysed by receiver operating characteristics curve.ResultsIn adults, TAT, SATtotal and SATtrunk increased linearly with increasing BMI and WC, whereas they followed a cubic function in children and adolescents with a steep increase at BMI and WC ≥1 standard deviation score and VAT at WC ≥2 standard deviation score. Sex differences were apparent in adults with women having higher masses of TAT and SAT and men having higher VAT. Using established BMI or WC cut‐offs, correspondent masses of TAT, SATtotal, SATtrunk and VAT increased from childhood to adulthood. In all age groups, there were positive associations between BMI, WC, SATtrunk, VAT and HOMA‐IR. When compared with normative cut‐offs of BMI or WC, HOMA‐IR‐derived cut‐offs of regional fat depots were lower in all age groups.ConclusionsAssociations between BMI, WC and regional fat depots varied between children, adolescents, young and older adults. When compared with BMI‐derived and WC‐derived values, an insulin resistance‐derived cut‐off corresponded to lower masses of regional fat depots. Thus, established BMI and WC cut‐offs are not appropriate to assess metabolic disturbances associated with obesity; therefore, new cut‐offs of BMI and WC are needed for clinical practice.

Reaching the Tipping Point: Identification of Thresholds at which Visceral Adipose Tissue May Steeply Increase in Youth

“…To our knowledge, this is one of the first reports of the existence of such thresholds in the pediatric population, yet it is important to note that similar thresholds have been reported in adults, with an almost identical cut point in women versus girls but a lower cut point in men versus boys . Initial observations of potential nonlinear relationships of BMI and waist circumference with VAT in children and adolescents have been previously reported. Our results are in agreement with these studies and extend the findings within the context of a much larger sample with a wider range of BMI/adiposity levels and a higher proportion of participants within the severe obesity category.…”

“…In this scenario, constraints on subcutaneous fat expandability in the presence of weight gain would be biologically disadvantageous and would potentially accelerate the development of cardiometabolic risk factors. Though some studies have reported nonlinear associations of BMI and waist circumference with VAT in children and adolescents , this “threshold hypothesis” has been incompletely investigated in the pediatric population, especially in youth with high levels of BMI consistent with severe obesity. However, the impetus to do so is supported by our previous observations showing that youth with VAT at or above the cohort mean had stronger associations of VAT with cardiometabolic risk factors compared with those below .…”

Age- and Sex-Related Percentiles of Skinfold Thickness, Waist and Hip Circumference, Waist-to-Hip Ratio and Waist-to-Height Ratio: Results from a Population-Based Pediatric Cohort in Germany (LIFE Child)

“…WHR (WC/HC) cutoff points are used to categorize the distribution of body fat in adults with the same BMI and help to define overweight in terms of “apple shape” or “pear shape.” It is known that central obesity (apple-shape, high WHR) contributes a higher risk than general obesity [27]. However, to date there are no established cutoffs for clinical practice with children and adolescents [28], likewise with WHtR, which is a more accurate tool for obesity diagnosis and a better prognosticator of associated health risks than BMI [28-30]. Circumference measurements are cheap and simple anthropometric methods, and both HC and WC are good predictors of intra-abdominal fat and cardiovascular risk factors [31-34].…”

Relationship of obesity to adipose tissue insulin resistance

“…This finding was similar to the result from the Manfred James Müller's study on peripheral insulin resistance. 22 In this study, most of the participants were most likely postmenopausal women (aged 50 years and over). They exhibit lower serum estrogen levels than premenopausal women, 23 and estrogen deficiency was associated with increased inflammation 24 and development of obesity-induced insulin resistance, which may be a reason for females in this study to exhibit higher adipo-IRI.…”