**Core Concept:** Understanding the definition and classification of body mass index (BMI) as a measure of obesity and its relation to health risks.

BMI is a mathematical formula that calculates an individual's body mass index based on their weight and height. It is calculated as weight (in kilograms) divided by the square of height (in meters). The World Health Organization (WHO) provides guidelines for interpreting BMI values:

1. Underweight: BMI < 18.5 kg/m² 2. Normal weight: BMI 18.5 to 24.9 kg/m² 3. Overweight: BMI 25 to 29.9 kg/m² 4. Obesity: BMI ≥ 30 kg/m² **Why the Correct Answer is Right:** The correct answer, "Overweight BMI," refers to a BMI value between 25 and 29.9 kg/m², which indicates an increased risk of health problems associated with excess body fat. This is because a higher BMI indicates higher body fat percentage, which is linked to a higher risk of chronic diseases such as diabetes, hypertension, and cardiovascular diseases. **Why Each Wrong Option is Incorrect:** A. Underweight BMI (BMI < 18.5 kg/m²): While underweight is generally considered a risk factor due to lower muscle mass and immune function, the focus here is on the overweight category. B. Normal weight BMI (18.5 to 24.9 kg/m²): This category represents a healthy BMI range, not relevant to the overweight question. C. Underweight BMI (BMI < 18.5 kg/m²): As mentioned before, underweight is not the focus here. D. Obesity (BMI ≥ 30 kg/m²): This category represents a severe obesity risk and is not applicable to the overweight question. **Clinical Pearl:** Monitoring and managing BMI is crucial for maintaining optimal health. Encouraging individuals with a BMI in the overweight range to adopt a balanced diet, regular physical activity, and lifestyle modifications can help prevent or delay the onset of obesity-related health problems. **Correct Answer:** Overweight BMI (25 to 29.9 kg/m²)