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Childhood obesity
Childhood obesity is defined by BMI percentile for age and sex (85th–94th overweight, 95th and above obesity), and most is "exogenous" in a child who is tall for age; an obese short child whose growth velocity has slowed needs a search for an endocrine or genetic cause.
Why it matters in the exam
The basic question is definition and calculation: BMI alone is not enough in a child — a percentile for age and sex is needed, and severe obesity is 120% or more of the 95th-percentile value. The more important question is the distinction: an obese, tall child with slightly advanced bone age — exogenous obesity; an obese child whose growth has stalled — think of hypothyroidism, Cushing syndrome or growth hormone deficiency.
The AAP 2023 guideline changed the approach: not "watchful waiting" but prolonged intensive health-behaviour and lifestyle treatment (at least 26 contact hours over 3–12 months). Pharmacotherapy is offered from age 12 (for example GLP-1 receptor agonists), and referral for bariatric surgery is considered from age 13 in severe obesity. From age 10, a child with obesity is tested for lipids, glucose (HbA1c or fasting glucose) and ALT.
The exam also asks about comorbidities: type 2 diabetes with acanthosis nigricans, fatty liver disease (MASLD), hypertension, obstructive sleep apnoea, slipped capital femoral epiphysis (SCFE) with a limp and knee pain, Blount disease, idiopathic intracranial hypertension, PCOS and depression. Genetic syndromes such as Prader-Willi (infant hypotonia, later hyperphagia, hypogonadism) and MC4R appear as early severe obesity before age 5.
Key points
- Overweight: 85th–94th percentile; obesity: 95th percentile or above.
- Severe obesity: 120% or more of the 95th percentile.
- An obese short child → endocrine work-up.
- From age 10: lipids, glucose and ALT in a child with obesity.
- Drugs from age 12; bariatric surgery considered from age 13 in severe obesity.
Summary table
| Situation | Definition or clue | Work-up | Approach |
|---|---|---|---|
| Overweight | BMI 85th–94th percentile for age and sex | Assess risk factors | Diet and activity counselling |
| Obesity | BMI 95th percentile or above | From age 10: lipids, HbA1c or fasting glucose, ALT | Intensive behavioural treatment; drugs from age 12 |
| Severe obesity | 120% or more of the 95th percentile | Full comorbidity work-up | Referral for bariatric surgery from age 13 |
| Obesity with slowing growth | Short child with slow growth velocity | TSH, cortisol, growth hormone work-up | Treat the endocrine cause |
| Genetic obesity | Onset before age 5 with severe hyperphagia, hypotonia or intellectual disability | Genetic tests (Prader-Willi, MC4R, leptin) | Cause-specific treatment |
A free exam question
A 16-year-old girl, with overweight and hirsutism, complains of irregular menstruation. Investigation that included prolactin levels, thyroid function, ACTH test, and urine collection for cortisol was normal. Which of the following findings would support the most likely diagnosis?
- A. Multiple follicles in the ovaries on an US
- B. Low levels of androstenedione in the blood
- C. Low LH levels relative to FSH levels in the blood
- D. Low levels of estrogen in the blood
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Sources
- AAP Clinical Practice Guideline for the Evaluation and Treatment of Children and Adolescents With Obesity, 2023 — Evaluation, comorbidity screening and treatment
- Endocrine Society Clinical Practice Guideline: Pediatric Obesity — Assessment, Treatment, and Prevention, 2017 — Endocrine and genetic evaluation
- Nelson Textbook of Pediatrics, 22nd edition (2024) — Overweight and Obesity
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.