A person with a BMI under 18 is categorized as which of the following?

Being categorized as underweight is based on the Body Mass Index (BMI) calculations, which are designed to assess an individual's weight in relation to their height. A BMI under 18 indicates that a person is significantly below the average weight for their height, suggesting potential health risks due to inadequate body mass. This can lead to nutritional deficiencies, weakened immune function, and other health issues. It's important to recognize that this classification highlights the need for nutritional support and intervention for individuals in this range to achieve a healthier weight.

The other classifications—normal weight, overweight, and obese—apply to higher BMI ranges, which do not correspond to a BMI under 18. Normal weight is typically classified within a BMI range of 18.5 to 24.9, while overweight and obesity are defined by progressively higher BMI thresholds, reflecting excess body weight that may pose health risks.