BMI Calculation for a 23-Year-Old Female
The BMI is 35 kg/m², which classifies this patient as Class II obesity.
Calculation Method
BMI is calculated as weight in kilograms divided by height in meters squared. 1, 2
For this patient:
- Height = 1.57 m (157 cm)
- Weight = 87 kg
- BMI = 87 ÷ (1.57)² = 87 ÷ 2.4649 = 35.3 kg/m²
This rounds to 35 kg/m², which is the correct answer from the options provided. 2
BMI Classification
According to the American Heart Association and World Health Organization guidelines, this BMI of 35 kg/m² falls into Class II (moderate) obesity. 3, 2
The standard BMI categories are: 3, 2
- Normal weight: 18.5-24.9 kg/m²
- Overweight: 25.0-29.9 kg/m²
- Class I obesity: 30.0-34.9 kg/m²
- Class II obesity: 35.0-39.9 kg/m² ← This patient
- Class III obesity: ≥40.0 kg/m²
Clinical Implications for This Patient
At BMI 35 kg/m², this patient requires comprehensive cardiovascular risk assessment and intensive weight management intervention. 3
The American College of Cardiology/American Heart Association guidelines recommend weight-loss treatment for all individuals with BMI ≥30 kg/m², with an initial goal of 10% body weight reduction. 3
Additional Assessment Required
Waist circumference measurement is NOT necessary in this patient because her BMI ≥35 kg/m²—it will almost invariably be elevated and adds no incremental risk information. 3
However, the following assessments ARE indicated: 3
- Fasting glucose, HbA1c, and fasting insulin to screen for diabetes/prediabetes
- Blood pressure, triglycerides, and HDL-cholesterol for metabolic syndrome
- Physical activity level (target ≥150 min/week moderate-intensity)
- Dietary habits and adherence to heart-healthy patterns
- Weight history, prior weight-loss attempts, and maintenance patterns
- Family history of obesity
- Review of medications that affect weight
Important Caveat
BMI has good specificity (90%) but poor sensitivity (50%) for detecting excess body fat, meaning it rarely misclassifies lean individuals as obese but frequently misses obesity in those with normal BMI. 1 However, at BMI 35 kg/m², this limitation is irrelevant—this patient definitively has obesity regardless of body composition. 4