What is the BMI classification and recommended management for a 50-year-old female, 5 feet tall, weighing 75 kilos?

BMI Calculation and Classification

This 50-year-old female with a height of 5 feet (152.4 cm) and weight of 75 kg has a BMI of 32.3 kg/m², which classifies her as Class 1 (mild) obesity, and she requires weight loss treatment with an initial goal of 10% body weight reduction. 1, 2

BMI Calculation

• BMI is calculated as weight in kilograms divided by height in meters squared: 75 kg ÷ (1.524 m)² = 32.3 kg/m² 1
• This calculation can also be performed using the formula: [weight (in pounds)/height (in inches)²] × 703 1

Classification According to Current Guidelines

The patient falls into Class 1 obesity (BMI 30-34.9 kg/m²) based on the World Health Organization and American Heart Association classification systems. 3, 1, 2

The obesity classification system defines:

• Normal weight: BMI 18.5-24.9 kg/m² 3, 1
• Overweight: BMI 25-29.9 kg/m² 3, 1
• Class 1 obesity (mild): BMI 30-34.9 kg/m² 1, 2
• Class 2 obesity (moderate): BMI 35-39.9 kg/m² 2, 4
• Class 3 obesity (severe/morbid): BMI ≥40 kg/m² 2, 4

Health Risk Assessment

• Class 1 obesity is associated with increased risk for cardiovascular disease, type 2 diabetes, hypertension, dyslipidemia, sleep apnea, and certain cancers. 1, 4
• Disease risk increases significantly when BMI exceeds 25.0 kg/m², with overall mortality beginning to increase at BMI levels greater than 25 kg/m² 3
• Cardiovascular and other obesity-related disease risks increase independently with increasing BMI and excess abdominal fat 3

Recommended Management Algorithm

Based on the American College of Cardiology guidelines, weight loss treatment is recommended for this patient because her BMI is ≥30.0 kg/m², with an initial goal of 10% body weight reduction (7.5 kg). 1, 2

Additional Assessment Required

• Measure waist circumference to assess central adiposity and further stratify cardiovascular risk. 1, 2, 4
  • For women, waist circumference >88 cm (>35 inches) indicates increased cardiovascular risk 1, 2
• Screen for obesity-related comorbidities including hypertension, dyslipidemia, type 2 diabetes, sleep apnea, and fatty liver disease 4

Treatment Components

High-frequency counseling (≥16 sessions in 6 months) focusing on nutrition, physical activity, and behavioral therapy is recommended. 4

• Caloric restriction to 1200-1500 kcal/day for women 4
• For women aged 51+ years, recommended daily energy allowance is approximately 1,900 kcal for light to moderate physical activity 3
• Physical activity should be incorporated as part of comprehensive lifestyle modification 1, 4

Pharmacotherapy should be considered as an adjunct to lifestyle interventions for patients with BMI ≥30 kg/m². 4

• GLP-1 receptor agonists (semaglutide, liraglutide) are particularly beneficial options 4
• Pharmacotherapy is recommended in combination with, not as a replacement for, lifestyle modifications 4

Monitoring

• During active weight management, monitor anthropometric measurements at least every 3 months 4
• Regularly assess for improvements in obesity-related comorbidities 4
• Even 3-7% weight loss improves glycemia and cardiovascular risk factors, though >10% weight loss provides greater benefits 4

Important Clinical Considerations

BMI has limitations as it does not distinguish between lean and fat mass, potentially misclassifying individuals with high muscle mass. 1, 2

• BMI has good specificity (90%) but low sensitivity (50%) for diagnosing excess adiposity 1, 2
• Waist circumference measurement provides additional information about central adiposity, which increases risk for cardiovascular and other diseases independent of overall obesity 1
• The combination of BMI and waist circumference provides more comprehensive risk assessment than BMI alone 1, 2