Obesity, Lipids, and Energy Metabolism
Obesity assessment
Use BMI percentile for age and sex; obesity is ≥95th percentile and overweight is 85th–94th. Assess blood pressure, fasting glucose or HbA1c, lipids, liver enzymes, and sleep symptoms. Most obesity is multifactorial. Endocrine causes are uncommon: hypothyroidism, Cushing syndrome, growth hormone deficiency, and hypothalamic injury. Syndromic obesity includes Prader-Willi, with hypotonia, hyperphagia, and hypogonadism, and Bardet-Biedl. Monogenic obesity involves leptin, leptin receptor, POMC, and MC4R pathways.
Lipids and traps
Screen children with obesity for dyslipidemia; familial hypercholesterolemia may present with tendon xanthomas or a strong family history. Do not use adult BMI cutoffs. Do not label a child as having constitutional delay or growth failure from obesity without measuring height velocity. Rapid weight gain with growth deceleration suggests an endocrine cause; obesity with tall stature is more typical of simple obesity. Metformin is not a weight-loss drug for most children. Treat persistent hypertension or dyslipidemia rather than assuming it will resolve.
Worked example
A 12-year-old with BMI 98th percentile has acanthosis nigricans, HbA1c 6.0%, and ALT 60. Screen for type 2 diabetes and fatty liver, counsel on nutrition and activity, and recheck in 3–6 months. If hypertension or dyslipidemia persists, treat.