An BMI of 18.5-29.9 kg/m2 is the normal range between malnutrition and obesity. BMI 25-29.9 kg/m2 is overweight in adults and greater identifies obesity.
BMI 30.0-34.9 is Grade I,
35.0-39.9 is Grade II and
greater than 40 kg is Grade III obesity.
Shortness in a race could change the proper scale to: normal 18.5-29.9, overweight 30.0-34.9 and obese 35.0-39.5.

However, the presently accepted BMI reads Grade I 30.0-34.9, Grade II 35.0-39.5 and Grade III over 40 BMI. BMI has the equation BMI = a + b/x.