Body mass index (BMI) is one’s weight in kilograms (2.2 kg per pound) divided by the height in meters-squared (1 meter = 39.37 inches). It is a measure that is often used to define health and body fat. It is also a measure that can be quite deceptive on paper—without knowing the individual.
A BMI of ≥30 kg·m2 is classified as obese.
A BMI of ≥25 kg·m2 is defined as the threshold for “overfat”, and a lower BMI is considered “healthy.” But wait a second….
Muscle is denser than fat. Excess muscle is healthier than excess fat. Conversely, under-muscled and under-fat is also unhealthy. So, BMI is meaningless without an understanding of body composition. Someone with a BMI of 20 kg·m2, for example, may have a high percent-bodyfat or they may be a very lean and moderately muscled athlete. Likewise, someone in the range of 25-30 kg·m2 may be over-fat or well-muscled (or somewhere in-between).
I will consistently argue that more muscle is always better—male or female. For some, this may mean an increase in BMI. What??! It may even mean moving into a category of “over-fat.”
Let’s look at this with some easy numbers: 220 lb (100 kg) and 78.75 inches (2 m). This individual has a BMI of 25 kg·m2. At 20% body fat (BF), the lean body weight is 176 lb. At a healthier 10% BF, the lean body weight increases to 198 lb (i.e., a 12 lb gain of muscle and loss of fat). BMI? Unchanged. Now suppose our subject gains 10 lb of muscle without losing any body fat (now 230 lb). The body composition improves to 19.1% BF (not a tremendous improvement, but likely a much-improved appearance). BMI, however, is now 26.1 kg·m2. More unhealthy? Not likely. Indeed, with more muscle mass the subject is now able to do more physical activity and will be on a path to possibly getting healthier. (And, at a higher body weight, will actually be able to eat more healthy food to maintain the weight!) More muscle is more metabolic. Over time, it will actually be easier to lose body fat.
What is one is at a higher BMI and over-fat. Shouldn’t they focus on caloric restriction and cardio to “burn” more calories and thereby lose fat? Caloric restriction? Yes. Cardio? Well, some. Muscle strengthening exercise, however, should not be neglected. Perhaps, the scale will not drop as quickly (though it could quite likely drop faster as the metabolism steadily increases to burn more fat rather than slowing to protect fat stores), but the change in appearance and health will be more dramatic.
For many, the goal of exercise might be to improve appearance. Ideally, though, the goal should be better health and longevity. The goal should be to be able to do more—not less—as we age. The goal should be to avoid hospitals and debilitating medical conditions. Numbers like body weight, BMI, waist circumference, and percent body fat are really just number that may or may not reflect one’s health. What is most important is that we are able to live our years well. Health and physical activity need not decline as we age. At the very least we should seek to slow the natural decline that is perceived to be caused by aging (which, in fact, is more a reflection of decreased physical activity—and poor diet). It is great to be able to say, “I weight the same as I did in high school,” but the mirror and a body composition test might tell a different tale.
There is no need to train like a bodybuilder, but a more hypertrophic approach to exercise may be warranted for better long-term health. Don’t be afraid to have a higher BMI, if it means you have gained muscle mass and strength. Focus on being healthier and increasingly more active.
Be your best today; be better tomorrow.
Carpe momento!
