What are the recommended investigations for an adult patient presenting with obesity?

Recommended Investigations for Obesity in Adults

All adults with obesity require basic anthropometric measurements (BMI and waist circumference), a comprehensive metabolic panel, fasting lipid profile, thyroid function tests, and screening for abnormal blood glucose, with additional targeted testing based on clinical findings. 1

Initial Anthropometric Assessment

• Measure BMI and waist circumference in all patients, as central obesity independently predicts mortality risk 1
• Waist circumference thresholds indicating increased risk: ≥88 cm (35 inches) for women, ≥102 cm (40 inches) for men 1
• Consider waist-to-hip ratio as an alternative measure of central adiposity 1

Physical Examination Findings to Document

The physical exam should specifically assess for:

• Acanthosis nigricans (darkened, velvety skin in body folds) indicating insulin resistance 1
• Hirsutism (excess facial/body hair) suggesting polycystic ovarian syndrome 1
• Large neck circumference (>17 inches in men, >16 inches in women) associated with obstructive sleep apnea 1
• Thin, atrophic skin with striae suggesting Cushing's syndrome 1
• Signs of hypothyroidism (dry skin, delayed reflexes, bradycardia) 2

Basic Laboratory Panel (Required for All Patients)

Core metabolic testing includes 1:

• Comprehensive metabolic panel (electrolytes, kidney function, liver enzymes)
• Fasting lipid profile (total cholesterol, LDL, HDL, triglycerides, non-HDL cholesterol) 1
• Thyroid-stimulating hormone (TSH) to screen for hypothyroidism 1, 3
• Hemoglobin A1C or fasting glucose for diabetes screening 1, 3
• Complete blood count 3

The U.S. Preventive Services Task Force specifically recommends screening for abnormal blood glucose in adults aged 40-70 years with overweight or obesity as part of cardiovascular risk assessment 1

Screening for Obesity-Related Comorbidities

Metabolic Syndrome Components

Screen for the presence of three or more criteria 1:

• Waist circumference ≥88 cm (women) or ≥102 cm (men)
• Triglycerides ≥150 mg/dL
• Fasting plasma glucose ≥100 mg/dL
• Blood pressure ≥130/85 mm Hg
• HDL cholesterol <40 mg/dL (men) or <50 mg/dL (women)

Cardiovascular Disease Screening

• Blood pressure measurement at every visit (hypertension defined as ≥130/80 mm Hg) 1
• Assess for symptoms of coronary artery disease, peripheral vascular disease, and heart failure 1
• Consider ECG if cardiovascular symptoms present 1

Sleep Apnea Assessment

Use validated screening tools for obstructive sleep apnea, particularly in patients with severe obesity 1:

• STOP-BANG questionnaire (scores ≥3 indicate high risk)
• Epworth Sleepiness Scale (scores >10 suggest excessive daytime sleepiness)
• Refer for polysomnography if screening positive 1

Liver Disease Evaluation

• Screen for metabolic-associated fatty liver disease (MAFLD) given high prevalence in obesity 1
• Elevated ALT/AST warrant further hepatic evaluation 1
• Consider hepatic ultrasound or FibroScan if transaminases elevated 1

Secondary Causes of Obesity (When Clinically Indicated)

Order additional testing only when history or physical examination suggests specific conditions 1, 2:

Endocrine Disorders

• 24-hour urinary free cortisol or late-night salivary cortisol if Cushing's syndrome suspected (central obesity, facial plethora, proximal muscle weakness, wide purple striae) 2
• Testosterone levels (total or free) in women with hirsutism, acne, or menstrual irregularities suggesting PCOS 2
• Prolactin level if menstrual irregularities or galactorrhea present 4
• Growth hormone stimulation testing if growth hormone deficiency suspected (rare, requires specialist referral) 2
• Testosterone levels in men with signs of hypogonadism 2

Genetic/Syndromic Obesity

Consider genetic testing referral if 2:

• Early-onset severe obesity (childhood)
• Hyperphagia (insatiable hunger)
• Developmental delay or intellectual disability
• Dysmorphic features or congenital malformations
• Strong family history of severe obesity

Additional Targeted Investigations

Cancer Screening

• Ensure adherence to age-appropriate cancer screening guidelines, as obesity increases risk for multiple malignancies (endometrial, breast, ovarian, prostate, pancreatic, colorectal, hepatic) 1

Mental Health Assessment

• Screen for depression using validated tools (PHQ-9) 2, 5
• Assess for binge eating disorder through clinical interview 2
• Evaluate for chronic stress and psychological barriers to weight management 2

Medication Review

• Document all current medications that may contribute to weight gain 1:
  • Psychiatric medications (antipsychotics, antidepressants, mood stabilizers)
  • Corticosteroids (systemic and high-potency topical)
  • Insulin and sulfonylureas
  • Certain beta-blockers
  • Anticonvulsants (valproate, gabapentin)

Lifestyle and Social Determinants

• Assess sleep quality and duration (poor sleep contributes to weight gain) 2
• Screen for food insecurity and housing stability 1
• Evaluate neighborhood environment and access to healthy food/physical activity 1

Common Pitfalls to Avoid

• Do not order extensive endocrine testing routinely—reserve for patients with specific clinical features suggesting secondary causes 2
• Do not overlook medication-induced weight gain—this is a common and modifiable contributor 1, 2
• Do not skip waist circumference measurement—BMI alone misses important metabolic risk from central adiposity 1
• Do not forget to screen for sleep apnea—it is highly prevalent but frequently undiagnosed in obesity 1

Risk Stratification

After completing investigations, use a clinical staging system to guide treatment intensity 1:

• Edmonton Obesity Staging System (EOSS) classifies patients into stages 0-4 based on presence and severity of obesity-related complications, mental health issues, and functional limitations 1
• Stage 0-1: No or subclinical complications (weight maintenance may suffice)
• Stage 2-3: Established complications or functional impairment (weight loss is clinical priority requiring intensive intervention) 1