Create a program that accepts a person's BMI score and outputs an appropriate comment on the score based on the following information:
For adults 20 years and older:
- A BMI below 18.5 is considered underweight.
- A BMI of 18.5 to 24.9 is considered healthy.
- A BMI of 25 to 29.9 is considered overweight.
- A BMI of 30 or higher is considered obese.