On the basis of BMI obesity is labeled at
**Core Concept**
Obesity is a complex condition characterized by an excess of body fat, which has significant implications for overall health. The World Health Organization (WHO) has established a body mass index (BMI) classification system to categorize body weight in adults. BMI is calculated by dividing an individual's weight in kilograms by the square of their height in meters.
**Why the Correct Answer is Right**
The correct answer is C. 30, as this is the threshold for obesity according to the WHO classification system. A BMI of 30 or higher indicates that an individual is obese, which increases their risk for various health problems, including cardiovascular disease, type 2 diabetes, and certain types of cancer. The WHO defines the following BMI categories: underweight (BMI < 18.5), normal weight (BMI = 18.5-24.9), overweight (BMI = 25-29.9), and obesity (BMI ≥ 30).
**Why Each Wrong Option is Incorrect**
**Option A:** A BMI of 20 is actually within the normal weight range, as it falls between 18.5 and 24.9. This option is incorrect because it does not meet the criteria for obesity.
**Option B:** A BMI of 25 is classified as overweight, not obesity. While individuals with a BMI of 25 may be at risk for developing health problems, they do not meet the threshold for obesity.
**Option D:** A BMI of 18 is actually below the threshold for normal weight, as it falls below 18.5. This option is incorrect because it is actually considered underweight.
**Clinical Pearl / High-Yield Fact**
It's essential to note that BMI is not a perfect measure, as it does not account for muscle mass or body composition. However, it remains a widely used and accepted tool for assessing weight status and identifying individuals at risk for obesity-related health problems.
**✓ Correct Answer: C. 30**