Dear Holly: What is BMI? -Body Mass What?
Dear Body Mass What: If you’ve been to a health screening lately or had an annual physical with your doctor, you may have heard the term BMI. What is it exactly, and what should yours be?
BMI stand for Body Mass Index and is one tool to assess your health. It is a measure of how much body weight you have relative to your height. Healthy range for adults is 18.5 to 24.9 kg/m2. It is simple and inexpensive to measure and is great for looking at large groups of people, like scientists do for research projects. Like any tool, BMI has pros and cons; it is not perfect. However, BMI is pretty accurate for most, especially for those who are sedentary.
One flaw is that BMI looks only at total weight, not type of weight. There is no distinction between fat or muscle. For this reason, your average athlete with a high amount of muscle tissue may register falsely as “overweight” according to their BMI. For those who are have a lot of muscle on their frame, they are healthy, even if their weight may be higher than a more sedentary person.
BMI is not appropriate to use during pregnancy. A pregnant woman will register as “overweight” because of the baby on board. We can use BMI to gauge how much weight would be healthy to gain during pregnancy. If a woman is overweight prior to becoming pregnant, it would be healthier for her to gain less weight than a woman who is normal weight.
To check your own BMI, look online for a free BMI calculator, or download a free app to do the math for you. I use a BMI calculator on my phone when working with clients.
What about kids? You can also assess their weight for their height using BMI, but the guidelines are dependent on their age and gender. The CDC has a BMI calculator for kids. Kids are growing, and a healthy weight depends on where they are on their growth continuum. A healthy toddler has chubby thighs and cheeks while a healthy 4-6 year old is quite lean.
One other simple tool that complements BMI is measuring your waist as well as a waist to hip ratio. Lean, healthy folks have a small waist. For men, we are aiming for less than 40 inches, ladies less than 35. For the ratio of waist circumference divided by hip circumference, men are striving for less than 1 and women less than 0.8. As one pound of muscle tissue is more compact than fat tissue, those with more of their weight coming from muscle will have a more compact frame.
Tip: pay attention to how your pants and belts are fitting. If you gain 5 pounds of fat and lose five pounds of muscle, the scale will not have budged an ounce, but your pants will be tighter. Conversely, if you improve your fitness, gain muscle and lose fat, don’t get frustrated if the scale isn’t budging, you are still a healthier person, as evidenced by your leaner, tighter frame.
BMI is just one tool to assess health. When doing a health assessment for yourself, also consider your waist circumference, your weight, your eating habits, what your usual beverages are, your stress level, your fitness level and usual hours per night of sleep. No single tool will perfectly assess health, but it can add dimension to the overall picture.
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What’s your question for Holly? Send them to firstname.lastname@example.org. For more information and to make an appointment to work on your goals, visit Grass Roots Nutrition, LLC and BrideBod, owned by me, Holly Larson, a Registered Dietitian. Visit me online at hollylarsonrd.com and follow us on Facebook. Have a delicious, healthy day!