Even though you may just now be hearing about the body mass index, or BMI, it’s not a new way to estimate your body fat — it’s a really old way. The formula for BMI was established almost 200 years ago by a Belgian mathematician who was trying to standardize people’s weight into categories of healthy and unhealthy.
While this formula can be very helpful as an indicator of obesity, it should never be used as the only tool. Dr. Nirav Naik at New Life Medical in Bakersfield, California, helps patients understand the value of the BMI calculator as well as its limitations.
Here, he clears up some common myths about BMI and shares the facts you need to know to use the tool wisely.
The BMI formula explained
The BMI formula hasn’t changed since its inception, except the earliest iteration was metric. The United States uses the Imperial system of pounds and inches, so it’s: weight (pounds) divided by height (inches)-squared, then multiplied by 703.
For a person who is 6 feet tall and weighs 200 pounds, the formula would be: 200 divided by 5,184 times 703, which equals a BMI of 27.1.
The next thing you need to know is exactly what that BMI number means. According to the Centers for Disease Control and Prevention (CDC), if your BMI falls between 18.5 and 24.9, you're considered within a healthy weight range. Below that, you’re underweight; above that, you’re overweight. Over 30 means you’re obese.
Those are the facts. Here are the myths.
Myth: A high BMI means you’re unhealthy
This is where strict adherence to BMI can take a downward turn. The formula doesn’t take into account all of the variables involved with body weight, and it can’t make any determinations about your health.
Consider the examples of four different people, all the same height and weight with a BMI of 26 — technically overweight, according to the index:
- One is a 75-year-old man
- One is a bodybuilder
- One is a pregnant woman
- One is sedentary teenager
The pregnant woman tips the scales because she’s carrying another human. The bodybuilder goes over the limit because of his muscle mass and bone density, which weigh more than fat. The elderly man crosses the line because fat accumulates as people age. The teen may have some weight-related health concerns.
Myth: A low BMI means you’re healthy
Wrong again. Generally speaking — which is the only way you can approach the BMI — mid-range numbers are better than high or low numbers. But everybody is different, and variables such as gender, hormones, age, and muscle mass can skew your BMI and cause you to jump to the wrong conclusion if you don’t pay attention to the context.
So, does a low BMI mean you’re healthy? Maybe. But it may also mean that you’re underweight, which can lead to its own set of problems — like a weak immune system, osteoporosis, and infertility.
Myth: BMI measures fat
BMI does not measure body fat. It’s merely a screening tool that gives you an idea of how you compare to other healthy adults. The fact is, BMI is most useful when it shows extreme results. Really high or really low numbers make it clear that, despite variables, you need to pay attention to your weight and how it’s affecting your health.
If your BMI is high, we run additional tests to get a more accurate picture of what’s going on. Skinfold calipers and circumference measurements, especially around your belly, allow us to evaluate your body fat composition and location.
Some fat lives just beneath your skin — called subcutaneous fat — and other fat hangs out deeper than that, near your organs — called visceral fat. Too much of either can be dangerous.
My BMI is high, now what?
While diet and exercise is a great place to start, weight loss isn’t always that simple. You can reduce calories in and increase calories out and still not see or feel results. When you’re struggling to shed pounds and overcome obstacles that make it difficult or impossible, you may be a good candidate for weight loss surgery.
Dr. Naik specializes in several procedures that can help you finally bring your BMI into the healthy range:
- Gastric bypass reroutes your digestive tract
- Gastric band cinches your stomach to make it smaller
- Gastric balloon fills some of the space in your stomach
- Gastrectomy removes of part of the stomach
When you consult with Dr. Naik and he evaluates your medical history and current condition, he can help you decide if surgery is right for you. Living life overweight or obese leads to other serious and life-threatening conditions. Take control of your weight by calling for an appointment or requesting one online today.