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Questions and Answers
Which factor is NOT considered an environmental cause of obesity?
What percentile indicates a child is classified as underweight?
What is the percentage range of heritability of BMI based on studies?
In clinical practice, which assessment is used for children and adolescents between the ages of 2–20 for obesity?
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Which class of obesity is defined as a BMI greater than 40 kg/m²?
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Monogenic obesity is typically linked to mutations in which pathway?
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What characteristic is often associated with obesity-related low-grade systemic inflammation?
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Which of the following is NOT a commonly cited psychosocial impact of obesity?
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What characteristic is typically associated with primary obesity?
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Which of the following endocrine disorders is associated with secondary obesity?
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What is a common genetic variant associated with monogenic obesity?
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What key factor is assessed when evaluating childhood obesity?
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Which psychosocial impact is commonly observed in children with obesity?
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What is likely to indicate an endocrine cause in a child with obesity?
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Which of the following medications is known to contribute to obesity?
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Which statement regarding lipid intermediates and insulin resistance is true?
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Which of the following skin findings is commonly associated with insulin resistance?
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Which sign is NOT associated with syndromic obesity?
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What is one of the recommended first steps to assess for glycemic dysregulation in children?
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Which of the following conditions is suggested by severe acne and hirsutism in pubertal girls?
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Which obesity-associated comorbidity may present with right upper quadrant tenderness?
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What test is suggested if liver function tests are elevated in a child?
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Which of the following features is characteristic of Bardet-Biedl syndrome?
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Which test would be appropriate for children exhibiting symptoms of disrupted sleep cycles and hyperactivity?
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Study Notes
Obesity Definition
- Obesity is an excess of body fat.
- It's estimated by the relationship between height and weight, considering age and sex.
Assessing Obesity
- Growth charts from the CDC or WHO are used to assess obesity.
- For children under 2 years old:
- Weight percentiles and weight-for-length charts are used.
- For children and adolescents ages 2-20:
- Body mass index (BMI) percentile is used.
- For children and adolescents ages 2-20 with BMIs greater than the 95th percentile:
- Percent of the 95th percentile is used.
Obesity Categories
- Underweight: less than the 5th percentile
- Healthy weight: 5th to 84th percentile
- Overweight: 85th to 94th percentile
- Class 1 obesity: 95th percentile to 119% of the 95th percentile
- Class 2 obesity: 120% to 139% of the 95th percentile or a BMI greater than 35 kg/m2 and less than 39 kg/m2
- Class 3 obesity: greater than 140% of the 95th percentile or a BMI greater than 40 kg/m2
Pathophysiology of Obesity
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Environmental Factors:
- High-calorie food supplies
- Large portion sizes
- Increased sedentary activities
- Decreased time spent in physical activities
- Television watching
- Use of electronic devices
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Genetic Factors:
- BMI heritability is estimated at 40%-70% based on studies.
- Single-gene mutation (monogenic) obesity is rare.
- Most single-gene mutations are connected to the leptin-melanocortin pathway.
Pathogenesis of Complications
- Adipocytes synthesize adipokines and hormones, which are affected by the amount and distribution of adipose tissue.
- Excess proinflammatory adipokines from adipocytes and macrophages within adipose tissue cause a low-grade systemic inflammatory state in obese individuals.
- Elevated levels of free fatty acids, inflammatory cytokines, and lipid intermediates in nonadipose tissues contribute to impaired insulin signaling and insulin resistance.
Etiological Classification
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Primary Obesity (Exogenous or Simple Obesity):
- Caused by unhealthy diet and lack of physical activity.
- Results in increased or consistent linear growth.
- Precocious puberty can occur.
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Secondary Obesity:
-
Endocrinopathies:
- Hypothalamic/pituitary dysfunction (with growth hormone deficiency)
- Hypercortisolism (Cushingoid features, consider a dexamethasone suppression test or 24-hour urinary free cortisol)
- Hypothyroidism (check thyroid-stimulating hormone [TSH], free thyroxine [T4] test)
- Pseudohypoparathyroidism
- Neonatal hyperinsulinemia
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Genetic syndromes:
- Down syndrome
- Beckwith-Wiedemann syndrome
- Accompanied by other behavior, functional, or anatomic abnormalities.
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Monogenic Obesity:
- Affects a minority of children with obesity.
- Alterations in a single gene lead to early-onset severe obesity.
- Common mutation: MC4R (melanocortin 4 receptor).
- Other forms: Leptin deficiency, leptin receptor variants, and POMC (pro-opiomelanocortin) mutation
- May be associated with syndromes like Prader-Willi or Bardet-Biedl.
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Medications:
- Antipsychotic drugs
- Glucocorticoids
-
Endocrinopathies:
Clinical Picture of Childhood Obesity
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Height and weight:
- Calculate BMI from weight and height, plot on appropriate growth chart.
- Compare weight gain with height gain.
- Normal or increased height and height velocity in exogenous obesity.
- Short stature and decreased height velocity suggest possible endocrine cause.
- Waist circumference at the level of the iliac crest.
- Central obesity more commonly seen in Cushing syndrome.
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Vital signs:
- Eg., bradycardia in hypothyroidism
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Skin findings:
- Striae caused by rapid weight gain.
- Violaceous striae may indicate Cushing syndrome.
- Acanthosis nigricans and skin tags may indicate insulin resistance.
- Severe acne and hirsutism in pubertal girls may suggest polycystic ovary disease.
- Striae caused by rapid weight gain.
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Signs associated with syndromic obesity:
- Neurodevelopmental delay
- Dysmorphic facial features
- Polydactyly
- Short stature
- Hypotonia
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Signs associated with underlying causes or complications of obesity:
- Abnormal gait, hip, knee, or foot tenderness, or limited range of motion in the hip.
- Hepatomegaly or right upper quadrant tenderness.
- Goiter.
- Premature appearance of secondary sexual characteristics in females.
- Pseudogynecomastia (adipose tissue mimicking breast development)
Complications and Associated Comorbidities
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Metabolic:
- Insulin resistance
- Type 2 diabetes
- Dyslipidemia
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Cardiovascular:
- Hypertension
- Coronary artery disease
-
Hepatic:
- Non-alcoholic fatty liver disease (NAFLD)
- Non-alcoholic steatohepatitis (NASH)
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Respiratory:
- Obstructive sleep apnea
- Asthma
-
Musculoskeletal:
- Osteoarthritis
- Pseudotumor cerebri
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Dermatological:
- Acanthosis nigricans
- Skin tags
- Striae
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Psychosocial:
- Low self-esteem
- Social stigmatization
- Depression
- Anxiety
Diagnostic Workup
- Fasting blood glucose or HbA1c test: To determine glycemic dysregulation.
- Fasting or non-fasting lipid profile: To assess dyslipidemia.
- Liver function tests (ALT and AST): To screen for NAFLD.
- 25-hydroxy (25OH) vitamin D test: Many children have vitamin D deficiency.
- Blood pressure: If the child is older than three years of age.
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Other studies based on history:
- Sleep study for snoring, daytime sleepiness, disrupted sleep cycle, or hyperactivity.
- Liver imaging if liver function tests are high.
- Uric acid level for children with diabetes, prediabetes, high-intake of high fructose corn syrup and table sugar.
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Description
This quiz explores the definition, assessment, and categories of obesity. It includes information on BMI percentiles and growth charts used for determining weight status in children and adolescents. Delve into the various classifications of obesity and the implications of excess body fat.
