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Overweight, obese adolescents more insulin-resistant than BMI-matched adults
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Overweight and obese adolescents have a lower visceral fat mass than their adult counterparts, but they are more insulin-resistant than sex- and BMI-matched adults, according to recent findings published in Obesity.
Moreover, researchers found that as early as adolescence, liver fat content is independently predictive of insulin resistance.
In a retrospective study, researchers extracted data on 39 obese or overweight adolescents and 39 BMI and sex-matched adults from two different studies conducted in Tübingen, Germany. Researchers took anthropometric measurements of study participants and assessed BMI as a continuous measure. In the adolescents, BMI data were categorized as age- and sex-specific percentiles, and the percentile value of each adolescent was projected to age 18 years. Using these projections, the researchers were able to identify adults with similar BMI for a matched comparison.
Using whole-body MRI, spectroscopy or blood work, the investigators also assessed the following for each participant: lean body mass, visceral fat mass, total subcutaneous and abdominal subcutaneous fat mass, liver fat content, fasting blood glucose and fasting insulin. They estimated insulin resistance using the homeostasis model assessment of insulin resistance (HOMA-IR).
The researchers found that adolescents had higher HOMA-IR (P<.001) and lower lean body mass (P=.002) than the adult participants. The adolescents also had higher total body fat mass (P=.02) but lower visceral fat mass (P<.001).
Although there was not a significant difference in mean fasting glucose between the groups, fewer adolescents had impaired fasting glucose vs. adults.
Liver fat content did not differ significantly between adolescents and adults (P=.16) and was found to be an independent predictor of insulin resistance in both groups (both P≤.007), but not total body or visceral fat mass (all P≥.64).
According to the researchers, the increased insulin resistance seen in adolescents may not be related to dysregulated adipokine, cytokine, myokine or hepatokine secretion, as is generally the case in obese adults.
“Rather than the body fat mass, the body fat distribution or the liver fat content, the altered sex-hormone levels and sex-hormone sensitivity, and the increased growth hormone
signaling may result in the hyperinsulinemia,” the researchers wrote. “These findings may be particularly relevant for future studies aiming at understanding the role of sex-hormone levels and sex-hormone sensitivity, as well as growth hormone signaling in the determination of body fat distribution and glucose metabolism in adolescents.”
Disclosure: This study was funded in part by the Tübingen University Hospital, the German Research Foundation and the German Federal Ministry of Education and Research to the German Center for Diabetes Research.
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