How To Calculate Your BMI, Why It Matters, And Some Other Numbers To Watch
While some people decide for themselves what they believe to be "overweight," if you asked your doctor where you stand, they would most likely start by determining your Body Mass Index, or "BMI."
The formula for BMI has been in use for over 100 years. It was devised way back in the 1830s by Lambert Adolphe Jacques Quetelet, a Belgian statistician and sociologist.Body Mass Index can be determined by dividing your weight (in pounds) by your height (in inches) squared, and multiplying the result by 703. You can also use one of the many BMI calculators out there, or this handy-dandy chart!
A BMI over 25 is qualified as an overweight one, and a BMI of 30 or more puts you into the obese category. If your BMI is over 40, you are considered morbidly obese and at an even greater health risk.
Those with overweight and obese BMIs have been found to be at higher risk for various health conditions, including coronary artery disease, type 2 diabetes, hypertension, osteoarthritis, sleep apnea, stroke, and many types of cancer.
On the other hand, a BMI under 18.5, which can be caused by malnutrition, eating disorders, or other health conditions that can interfere with your absorption of nutrients, qualifies you as underweight. This puts you at risk for a whole 'nother set of health problems, including osteoperosis, decreased immune function, and fertility issues. As Goldilocks learned, your best bet is to stay in the just-right middle, between 19 and 24!
But BMI isn't a foolproof formula. It doesn't, for instance, take into account muscle weight, so it shouldn't be used to assess the health of hardcore athletes. It also is unsuitable for pregnant women, the elderly, or children (who should instead be compared against other children of the same sex and age).
And since the number used for division in BMI is the same no matter your height, some suggest that it misleads short people into thinking that they are, relatively, thinner than they are, while tall people are misled into thinking they are relatively fatter.
It's also a far-from-perfect measure of overall health; many overweight and obese Americans have been found to be healthy by cardiometabolic measures, while many "normal-weight" people can still have worrisome health profiles.
Another way of evaluating whether someone is overweight or not is by measuring what percentage of their body consists of fat. For women, 10 to 13 percent fat is healthy, but over 32 percent is considered a sign of obesity; for men, 2 to 4 percent fat is considered healthy, and over 25 percent is classed as obesity. You can measure your body fat percentage with a tool called a caliper, or with a specialized scale.
You can also calculate it yourself. If you're a man, measure the circumference of your abdomen and neck, then subtract the neck value from the abdomen's. Women should add the measurements of their waist and hips and then subtract the measurement of their neck.
Fat around the abdomen is considered the most risky, so waist circumference itself is also sometimes used to determine metabolic health. For women, a healthy waist circumference is less than 35 inches. For men, it should be less than 40 inches.
Check out these numbers to give yourself an idea of where you stand and how much weight you should aim to lose, but don't obsess over them! Focusing on eating clean, healthy foods will almost definitely get your body where it needs to be.