When a weight-care sign-up form turns you down over your body mass index, or BMI, the no rests on a screening measure that is not intended to diagnose disease or illness. You can work that number out yourself, see where it sits against the two BMI cut-offs for a weight-management medication, and bring your own doctor what a BMI leaves out.
What your BMI is calculated from
Your BMI is calculated from your weight and your height and nothing else, and it is a measurement used to estimate overweight and obesity. In US units, multiply your weight in pounds by 703, divide that answer by your height in inches, then divide that answer by your height in inches again.
In metric units it is your weight in kilograms divided by your height in meters squared. An adult who is 5 feet 8 inches tall and weighs 200 pounds has a BMI of 30.4, which falls in the obesity category.
To check a number a sign-up form showed you, enter the same height and weight in CDC's adult BMI calculator. The result lands in one of these categories:
- Underweight, below 18.5
- Healthy Weight, 18.5 to 24.9
- Overweight, 25.0 to 29.9
- Obesity, 30.0 or greater, in three classes starting at 30.0, 35.0 and 40.0, with the third also called severe obesity
Every adult 20 and older is read against those same categories, regardless of age, sex, or race. Children and teens are read another way: because they are still growing, their BMI is compared with other children and teens of the same sex and age. An adult BMI calculator is not for evaluating a child. For a child's number, talk to your child's doctor about the right weight for your child's age.
How much your BMI can tell anyone about you
Your BMI can tell you about body fat only indirectly. For most people it is a good indicator of whether they have too much or too little body fat, though it is not a direct measure of body fat. It cannot tell fat apart from lean body mass, meaning muscle and bone, and it cannot show where in the body the fat is located. It does line up moderately to strongly with other measures that capture the amount, type and spread of fat, and a health care provider can help evaluate the health risks tied to your BMI and your body fat. A BMI outside the healthy weight range can increase a person's risk for certain health problems, and people in the obesity category are at increased risk for type 2 diabetes, heart disease and other health problems.
If you have more or less muscle than is normal, your BMI may not be a perfect measure of how much body fat you have. Because muscle weighs more than fat, people who are very muscular may have a high BMI, and on BMI alone, someone with a lot of muscle might land in the overweight category or the obesity category.
The cut-offs between the categories do not move with age, but healthy weight ranges for older adults are different than for other age groups, so the Healthy Weight category may not be the range that fits an older adult. An older adult with a normal BMI may have less muscle than others who are slightly overweight. If you are 65 or older, a slightly higher BMI may help protect you from thinning of the bones, called osteoporosis. Talk to your doctor before you try to lose or gain weight.
Despite those limits, BMI is a quick, inexpensive and reliable screening measure of a person's weight relative to their height.
Why one place turned you away on your BMI and another let you through
A weight-management medication has two BMI cut-offs, and only the lower one depends on your health, so an eligibility rule that uses only the higher cut-off can turn away a number that a rule using both would let through. Health care professionals use BMI to help decide whether you might benefit from that kind of medication, and your health care professional may prescribe a weight-management medication if you are an adult with:
- a BMI of 30 or greater, or
- a BMI of 27 or greater, together with a weight-related health problem such as high blood pressure or type 2 diabetes
If your BMI sits between those two cut-offs, only the second can let you in, and only if you have a weight-related health problem such as high blood pressure. The first cut-off is where the obesity category starts, and the second sits inside the overweight category, so a person whose BMI is 27 to 29.9 and who has high blood pressure can meet the second. Work out your own number with the steps above to see which side of each cut-off it sits on.
High blood pressure and type 2 diabetes are among the weight-related health problems that count. If another condition is in your history, ask your doctor whether it is one of them.Weight management medications are meant to help people who have health problems related to overweight or obesity, and they aren't for everyone with a high BMI: clearing either cut-off makes you someone a health care professional may prescribe for, not someone who will be. A health care professional can also assess your individual risk caused by your weight.
Bringing your doctor more than a BMI
Bring your doctor a waist measurement as well as your BMI, since a BMI cannot show where your body carries its fat. To measure your waist, stand, place a tape measure around your middle just above your hipbones, and take the reading just after you breathe out. Fat carried mostly around the waist rather than at the hips raises the risk of heart disease and type 2 diabetes, and so does a waist of more than 35 inches for women or more than 40 inches for men.
Your provider may also take your waist circumference and waist-to-hip ratio into consideration, and your doctor can take both measurements during your appointment and compare them with the reading you took at home.
Your medical history belongs at the same appointment, starting with the condition that got you through at the second place. For a more complete picture than a BMI gives, health care providers should consider other factors, which may include a patient's medical history, health behaviors, physical exam findings and laboratory findings. A blood result already in your patient portal is one of those laboratory findings, so bring it too (see An A1C result nobody explained, and when to test again). For health behaviors, a few days kept in a food diary can show how you eat when no day is typical (see A food diary for the doctor when none of your days is typical).
Then ask your doctor what your BMI means for you, with your waist, your history and your age in front of you both. If your BMI is above the healthy weight range, your doctor might look for possible reasons for the excess weight and recommend support or treatment.
With NicoCares, a physician prescribes, and the platform never does.If you are already a patient, ask your care team what your BMI means for your treatment through Spruce, the secure messaging Spruce Health hosts between you and your care team, and attach the waist reading you took at home; your own doctor can repeat that measurement, and take your waist-to-hip ratio, at your appointment.
