Approach
Diagnosis is based primarily on a thorough history and examination in conjunction with the child's body mass index (BMI). Waist circumference and skinfold thickness may be used to support the diagnosis. Imaging techniques are rarely used.
History
Many children do not present with a specific complaint of obesity or rapid weight gain; thus, screening for excess adiposity is important at all visits.
Review environmental, social, and family factors that may contribute to obesity and influence the likelihood of successful treatment.[42][57]
Children who have one or two parents with obesity are at higher risk of developing obesity, as are children who are overweight at a young age, non-Hispanic black children and Hispanic children, and children raised in families of lower socioeconomic status.[5][17][25] Maternal history of gestational diabetes, weight gain or obesity during pregnancy, or poor nutrition during pregnancy should be noted.[24][25] The child may have been born small for gestational age.
Reviewing dietary history is important to assess potential modifiable dietary choices. Assessing daily exercise patterns is also important, as sedentary behavior (e.g., computer/television screen time >2-3 hours/day) has been associated with obesity.[27][28] Enquire specifically about the duration, intensity, and type of physical activity.[58]
Patients may present with symptoms of complications/comorbidities associated with obesity including:
Headache (associated with hypertension and pseudotumor cerebri)
Snoring or daytime somnolence (obstructive sleep apnea)
Abdominal pain (cholelithiasis)
Hip pain (slipped capital femoral epiphysis)
Polyuria or polydipsia (type 2 diabetes)
Irregular menses and/or hirsutism (polycystic ovary disease).
A full medical and family history should also be obtained as indicated to rule out other causes of obesity due to disease such as hypothyroidism, Cushing syndrome, pseudohypoparathyroidism, and hypothalamic obesity following surgery for a craniopharyngioma.
Medication history for drugs including neuropsychiatric medications, corticosteroids, antibiotics, and acid-suppressing agents should be elicited.[31][32][59]
Enquire about psychosocial consequences of obesity: for example, bullying, teasing, and low self-esteem. Ask specifically about any disordered eating habits or attempts to lose/control weight. Children may use unhealthy methods such as vomiting, laxative misuse, or diet pills, in an attempt to lose or control weight.[60] Binge eating (eating large amounts in the absence of hunger) is common among children and adolescents with overweight/obesity, and is associated with increased hours of screen time.[61] Obesity increases a child's risk of anxiety and depression.[62][63]
Children with gene mutations present with severe, early-onset obesity, usually associated with disruption of normal appetite control mechanisms.
Physical exam
Children with overweight or obesity have a higher prevalence of hypertension; thus, blood pressure should be measured.[3][64] Acanthosis nigricans may be seen in children with obesity and is associated with insulin resistance. Acne and/or hirsutism may be associated with polycystic ovary syndrome.
Short stature associated with obesity should raise the suspicion of a hormonal abnormality as the cause of obesity (e.g., hypothyroidism, Cushing syndrome). Developmental delay, dysmorphic features, and hypogonadism in addition to short stature suggest a genetic syndrome such as Prader-Willi and Bardet-Biedl syndromes. Hypogonadism may also be present with leptin deficiency, and red hair and hypocortisolism are observed in pro-opiomelanocortin deficiency.
Indices of body fat
BMI
The most widely accepted measure of body fat is the BMI (weight in kilograms divided by height in meters squared).[64] Accurate measurements of both height and weight are therefore very important.
Abnormal BMI cutoffs in children are determined by age- and sex-specific percentiles based on the Centers for Disease Control and Prevention growth charts.[2] A BMI between the 85th and 94th percentile is defined as overweight.[4][64]
Obesity is classified as:[3][5][6][65]
Class 1 (BMI ≥95th percentile)
Class 2 (BMI 120% to 139% of the 95th percentile, or an absolute BMI of ≥35 kg/m² to <40 kg/m², whichever is the lower for age and sex)
Class 3 (BMI ≥140% of the 95th percentile, or an absolute BMI ≥40 kg/m², whichever is the lower for age and sex).
For children <2 years of age, BMI normative values are not available. Weight-for-height values above the 95th percentile in this age group can be categorized as overweight.[7]
Although BMI is an indirect measure of body fat, it has been found to correlate with adiposity.[1][66] However, it does not distinguish between subcutaneous and visceral fat (the latter having been shown to be associated with cardiovascular and metabolic risk factors).[67][68] Children who are very muscular may have a BMI in the abnormal range despite having normal to low adiposity.
Waist circumference
Waist circumference or waist-hip ratio can be used as an indirect measure of visceral adiposity (which has been shown to be associated with cardiovascular and metabolic risk factors).[67][68]
Measuring waist circumference is noninvasive and may be helpful in addition to BMI to identify overweight children at a higher metabolic risk.
Waist circumference percentiles have been developed for children ages 2 to 19 years.[2] However, the cutoff values that would indicate risk above that of BMI measurement are not available.[59]
In adults, waist circumferences >40 inches (>102 cm) for men and >34 inches (>88 cm) for women are associated with an increased risk of metabolic problems.[69]
Growth charts can be found at the Centers for Disease Control and Prevention: CDC: growth charts Opens in new window The World Health Organization 2006 growth standard is recommended in many countries for children ages 0-5 years, and for children ages 0-2 years in the US. WHO: Child growth standards. Opens in new window
Investigations
Investigations to screen for common complications/comorbidities:[18][64][70]
Fasting lipoproteins to screen for dyslipidemia in children over the age of 10 years, with a BMI ≥85th percentile
Fasting glucose, a 2-h plasma glucose during a 75-g oral glucose tolerance test, or hemoglobin A1c to screen for type 2 diabetes mellitus in children with obesity, or overweight and over the age of 10 years
Liver function tests (LFTs) to screen for nonalcoholic fatty liver disease in children with obesity, or overweight and over the age of 10 years.[71][72]
Investigations to identify medical causes of obesity depend on the patient's symptoms and presentation (e.g., short stature, fatigue, violaceous striae, hirsutism, irregular menses, or dysmorphic features) but could include:
Thyroid function tests for hypothyroidism
Urinary free cortisol or midnight salivary cortisol for Cushing syndrome
Serum calcium, phosphate, and parathyroid hormone for pseudohypoparathyroidism
Hypothalamopituitary testing in hypothalamic obesity following surgery for craniopharyngioma
Therapeutic trial of discontinuing medications suspected of causing obesity, where possible[59]
Genetic testing in patients suspected of having:
Monogenic obesity
Bardet-Biedl syndrome
Prader-Willi syndrome.
Appropriate tests for the primary care physician to obtain include fasting lipoproteins, fasting glucose or hemoglobin A1c, a comprehensive metabolic panel, and thyroid function tests. The physician should consider referring the patient to a pediatric endocrinologist if any of these tests are abnormal, or if more specific tests such as urinary free cortisol, midnight salivary cortisol, pituitary hormones, or genetic testing are thought to be needed.
Comorbidities
In a review of studies, the American Academy of Pediatrics found that the prevalence of abnormal lipid values and glucose metabolism, and raised blood pressure and mean alanine transaminase varied with weight classification. It found children with overweight or obesity to be associated with greater comorbidity prevalence.[72] Overall, however, the results showed that the vast majority of children, even those with obesity, have normal values.[72]
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