New Delhi, July 27 -- A mother brought her twelve-year-old son to my clinic last year because she had noticed a dark, velvety patch on the back of his neck. She had been scrubbing it for weeks, convinced it was dirt. It was not dirt. It was acanthosis nigricans, a skin change that appears when insulin levels in the blood have been running high for a long time. His fasting glucose was normal. His HbA1c was unremarkable. His ultrasound showed a fatty liver, and his fasting insulin was more than three times what it should have been at his age.

Are parents the cause of childhood obesity?

This is the part of childhood obesity that parents rarely see. The weight is visible. The metabolic damage underneath it is not. That is not how the biolog...