How to write the health evaluation with body mass index below 18.5?

The health evaluation with body mass index lower than 18.5 says: It is suggested to strengthen nutrition, eat more fruits and vegetables and drink more milk and eggs. Body mass index (bmi)= weight (kg)/ height (m2), which is one of the important indexes to evaluate the body shape, nutritional status and obesity. According to the proportion of adult residents in China with different bmi intervals to the total population, B and I were divided into normal interval (18.5-23.9) and low weight (