destitute nutrition or underlying health conditions can result in adults being underweight. Results from the 2013-2014 National Health and Nutrition Examination Survey (NHANES),using measured heights and weights, indicate that an estimated 1.4% of U.
S. adults aged 20 and over are underweight. Body mass index (BMI), or expressed as weight in kilograms divided by height in meters squared (kg/m2),is commonly used to classify underweight (BMI less than 18.5) among adults aged 20 and over.
Source: cdc.gov