Workup for Weight Loss in a Teenage Male
The first critical step is determining whether this is intentional or unintentional weight loss, as this fundamentally changes the diagnostic and management approach. 1
Initial Assessment: Distinguishing Intentional from Unintentional Weight Loss
For Unintentional Weight Loss
Plot height, weight, and BMI on CDC 2000 growth charts and compare with as many previous data points as possible to identify the trajectory and severity of weight loss. 1
- A BMI below the 5th percentile is underweight and may indicate an eating disorder (ED). 1
- An unusually rapid decline in BMI percentile, even in normal-weight or overweight adolescents, raises concern for an ED. 1
- Missed menstrual periods in girls is another indicator of possible ED. 1
Comprehensive Physical Examination and Review of Systems
Conduct a thorough physical examination specifically assessing for vital sign instability and signs of malnutrition or underlying organic disease. 1
High-risk clinical findings requiring urgent evaluation include: 1
- Bradycardia (heart rate <50 beats/minute during the day)
- Hypotension (<90/45 mm Hg)
- Hypothermia (body temperature <96°F [<35.6°C])
- Orthostasis (increase in pulse >20 beats/min or decrease in blood pressure >20 mm Hg systolic or >10 mm Hg diastolic on standing)
Screen for high-risk eating and activity behaviors: 1
- Severe dietary restriction (<500 kcal/day)
- Skipping meals to lose weight
- Prolonged periods of starvation
- Self-induced vomiting
- Use of diet pills, laxatives, or diuretics
- Compulsive and excessive exercise
- Social isolation, irritability, profound fear of gaining weight, body image distortion
Laboratory Workup for Unintentional Weight Loss
If the baseline evaluation (clinical examination, standard laboratory tests, chest X-ray, and abdominal ultrasound) is completely normal, major organic and especially malignant diseases are highly unlikely. 2
Standard laboratory examination should include: 2
- C-reactive protein
- Albumin
- Hemoglobin
- Liver function tests
In one prospective study of 101 patients with unexplained weight loss, a completely normal baseline evaluation was found in 0% of patients with malignancy, 5.7% with non-malignant organic disease, and 52% without physical diagnosis. 2 This suggests that when the baseline workup is entirely normal, a watchful waiting approach may be preferable to undirected invasive testing.
For Intentional Weight Loss (Overweight/Obesity Context)
If the teenage male is attempting weight loss due to overweight or obesity, assess BMI percentile and screen for obesity-related comorbidities. 1
Comorbidity Assessment
Specific assessment for comorbidities is strongly recommended when BMI ≥95th percentile. 1
Screen for: 1
- Hypertension
- Dyslipidemia
- Type 2 diabetes mellitus (T2DM)
- Impaired glucose tolerance
- Insulin resistance
Additional obesity-related conditions to evaluate include: 3
- Obstructive sleep apnea
- Nonalcoholic fatty liver disease
- Musculoskeletal problems
- Psychosocial issues (depression, anxiety, social stigmatization)
Laboratory Workup for Obesity-Related Weight Loss
For adolescents with BMI ≥95th percentile, obtain: 1
- Fasting glucose and hemoglobin A1c
- Lipid panel
- Blood pressure measurement
- Liver function tests (if nonalcoholic fatty liver disease suspected)
If presenting with marked hyperglycemia (blood glucose ≥250 mg/dL) without acidosis but with symptoms of polyuria, polydipsia, nocturia, and/or weight loss, initiate basal insulin while starting metformin. 1
If presenting with ketosis/ketoacidosis, obtain: 1, 4
- Complete metabolic panel
- Venous blood gases (pH, bicarbonate)
- Serum ketones (preferably direct β-hydroxybutyrate measurement)
- Urinalysis
- Complete blood count
DKA diagnostic criteria include: 4
- Blood glucose >250 mg/dL
- Venous pH <7.3
- Serum bicarbonate <15 mEq/L
- Moderate ketonuria or ketonemia
Common Pitfalls to Avoid
Do not dismiss weight loss in normal-weight or overweight adolescents as "healthy dieting"—disordered eating behaviors can occur at any weight and require evaluation. 1
Do not rely solely on urine ketones for diagnosis or monitoring of ketoacidosis—direct blood β-hydroxybutyrate measurement is preferred. 4
Do not assume psychiatric causes without completing a thorough organic workup first, but recognize that psychiatric disorders (especially eating disorders) are common causes of weight loss in adolescents. 1, 2
Early diagnosis and intervention for eating disorders are associated with improved outcomes, so maintain a low threshold for referral to a multidisciplinary ED team. 1