The Coast Guard requires a Body Mass Index calculation on your physical exam form. If your BMI is 40 or above, you may be required to submit a letter from an occupational therapist or a physician stating that you have demonstrated performance of certain physical tasks, such as climbing ladders or pulling a fire hose over a distance. You may also be required to submit a sleep study to rule out sleep apnea, which is common complication for those who are obese.

The BMI formula is a simple combination of your height and weight, which is designed to provide valuable information concerning the health of an individual. The number determines whether or not you are at a healthy weight for your height or if you are overweight, obese or even underweight.