Laboratory Workup for Patients with Obesity Seeking Weight Loss
The recommended laboratory workup for patients with obesity seeking weight loss should include a comprehensive metabolic panel, fasting lipid profile, thyroid function tests, and blood glucose screening. 1
Initial Laboratory Assessment
Core Laboratory Tests
- Comprehensive metabolic panel - to assess liver function, kidney function, and electrolyte balance 1
- Fasting lipid profile - to evaluate cardiovascular risk 1
- Thyroid function tests - to rule out hypothyroidism as a contributor to weight gain 1
- Blood glucose screening - hemoglobin A1C or fasting glucose to assess for diabetes or prediabetes 1, 2
Additional Tests Based on Clinical Presentation
- Complete blood count - to assess for anemia and other hematologic abnormalities 2
- Liver function tests - particularly important when evaluating for non-alcoholic fatty liver disease (NAFLD) 1
- Specific hormone testing - if clinical suspicion of endocrine disorders exists 1
Targeted Testing Based on Risk Factors and Symptoms
Sleep Disorder Evaluation
- Consider sleep studies for patients with symptoms suggestive of obstructive sleep apnea (OSA) or obesity hypoventilation syndrome, particularly those with large neck circumference 1
- Screening tools like the Epworth Sleepiness Scale and STOPBANG questionnaire can help identify candidates for sleep studies 1
Cardiovascular Assessment
- ECG to check for evidence of coronary heart disease and establish a baseline 1
- Consider exercise stress testing in patients with cardiac symptoms or multiple cardiovascular risk factors 1
Secondary Causes of Obesity
- Targeted testing if history and physical exam suggest secondary causes of obesity (e.g., Cushing's syndrome, hypothyroidism) 1
Clinical Context for Laboratory Testing
Anthropometric Measurements
Laboratory testing should be interpreted in the context of:
- BMI calculation (weight in kg/height in m²) 1
- Waist circumference (≥88 cm for women, ≥102 cm for men indicates increased risk) 1
- Physical examination findings such as acanthosis nigricans (insulin resistance), hirsutism (polycystic ovarian syndrome), or thin atrophic skin (Cushing's disease) 1
Timing and Frequency
- Baseline testing before initiating weight loss interventions 1
- Follow-up testing to monitor progress and adjust treatment plans 3
- Regular monitoring every 4-6 weeks during active weight loss phase 3
Interpreting Results
Metabolic Risk Assessment
- Use laboratory results to identify components of metabolic syndrome:
- Elevated triglycerides (≥150 mg/dL)
- Reduced HDL cholesterol (<40 mg/dL in men, <50 mg/dL in women)
- Elevated fasting glucose (≥100 mg/dL)
- These findings, along with elevated blood pressure and increased waist circumference, constitute metabolic syndrome 4
Treatment Planning
- Laboratory results help determine appropriate weight loss targets:
Common Pitfalls to Avoid
- Overlooking thyroid function - Hypothyroidism can contribute to weight gain and make weight loss more difficult 1
- Failing to screen for diabetes - Undiagnosed diabetes affects treatment approach and targets 1, 2
- Not considering medication effects - Many medications can contribute to weight gain; review current medications as part of workup 2
- Inadequate follow-up testing - Laboratory parameters should be monitored throughout weight loss journey to assess metabolic improvements 3
- Focusing solely on BMI - Laboratory abnormalities can exist in patients with normal BMI but increased visceral adiposity 7
By systematically evaluating these laboratory parameters, clinicians can identify obesity-related complications, establish baseline values for monitoring progress, and develop personalized weight management strategies that address each patient's specific metabolic risks.