Does this index make me look fat?

Weight is a funny thing. It seems that experts can never agree on what constitutes the "right" weight. Should we eat a low calorie diet and be a little underweight? Should we be a little overweight? Who decides what is overweight or underweight anyway? One of the sticking points in these conversations is the Body Mass Index, more commonly known as BMI.

I recently told a friend that I was trying to reach a healthy BMI. He immediately went off on how BMI is a scheme concocted by capitalism and physicians to scare the American populace into losing weight, and how I should not even try to reach a healthy BMI because I might kill myself in the process. Now, I don't put much stock in such an extreme reaction, especially since this same person told me I couldn't be "serious" about losing weight without restricting my exercise to only cardio and cutting out certain "bad" foods. I'm certainly trying to exercise and eat healthier for better reasons than to reach a number on a scale. But it did get me wondering: how good of a goal is a healthy BMI?

BMI is a measurement calculated by taking a weight (in kilograms) and dividing it by a height (in meters) squared. It was originally designed in the mid-1800s, and first started to be used as a proxy for body fat percentage in the 1970s. Despite warning that BMI should only be used on a population level and not to determine any one individual's health, it is currently used by insurance companies and physicians as a diagnostic tool for personal obesity. In the average person, BMI can aid physicians in determining who may be at increased risk. Anything below 18.5 is considered underweight, while 18.5 to 24.9 is considered normal. 25 to 29.9 makes you overweight, and anything over 30 enters you into the "obese" categories.

Take a look at this handy-dandy chart!

The problem with BMI is that it cannot distinguish between fat and lean body mass. This means that it fails to mark some people as obese who have excess body fat, while it marks some people (like athletes) as obese who clearly do not have excess body fat. It also fails to adjust for the extremes of height, which gives taller people a deceptively high BMI and shorter people a deceptively low BMI. At least one physician has altered the formula to correct for this, and you can view the comparison between the two here.

So if BMI is so flawed, how can we use it? A study conducted in 2007 looked at the relationship between BMI and body fat percentage in college students: males and females, athletes and nonathletes. They suggested altering the cutoffs for what should be "overweight" and "obese" based on the population being examined. For example, if you're a female athlete, your cutoff for overweight should be 27.7, but if you're a female nonathlete your cutoff should be 24.0. Linebackers shouldn't be considered overweight until they reach above 34.1. Clearly, there's a lot of wiggle room.

Why not just measure body fat? Measuring body fat percentage directly is a real chore, requiring an individual to wear special clothing and be submerged in a water or gas chamber with trained personnel at special sites. Slightly more intensive than hopping on a scale and backing up against a wall. Even the body fat percentage calculated by electrical currents or measurements with skin calipers can be way off if performed by inexperienced people or on someone with significant obesity.

The BOD POD method of measuring body fat

But there are other measures that can add good information to BMI. For example, waist-to-hip ratio is a good indicator of how much fat a person stores in the belly. Where you store your fat is just as important as how much of it you have. More fat around the abdomen (i.e., a higher waist-to-hip ratio) is associated with poorer health outcomes than more fat around the hips or thighs. Your level of cardiovascular fitness is also important, like the fastest possible speed you can run on a treadmill.

So my original question: how good of a goal is a healthy BMI? I think no one would argue that I am an athlete, and I'm smack dab in the middle of the curve as far as height. So none of the pitfalls of using BMI apply to me, and I can trust that my BMI correlates with my body fat percentage fairly well. If anything I should aim a little lower than the upper end of "normal" given the 2007 study. For me, at least, BMI is a good measure of progress in my attempt to get healthier, in addition to waist-to-hip ratio and cardiovascular fitness.

What do you think about using BMI? Is it fair for physicians to calculate BMI and potentially base treatment decisions on it? Should we be required to obtain other complementary information to get a more complete picture of a patient's obesity status?

Fancy seeing you again!

I've been away from the blog for a while. First there were away rotations to make a good impression on, then a giant test to study for, then applications to submit, then interviews to attend. The thing about medicine is there's always something that makes you "really busy", something coming up that you can use as an excuse not to do something. The trick is going to be finding a way to do the things that are important to me anyway. And, despite my small number of posts, this blog is important to me.

I mentioned that I'm going on interviews. For those of you unfamiliar with the process, during the fourth and final year of medical school, students must decide what specialty they are going to train in. When we graduate from medical school in May, we will receive our diploma, become doctors, and have the much-worked-for M.D. placed after our names. However, we can't just go out and hang up our shingle and start practicing medicine on patients. No no, first we have to complete a residency. While we do finally get paid during this period (hooray!), we are still under constant supervision and continuing to learn, albeit less than a medical student. We will be known as "residents", and this process could take anywhere from 3 to 7+ years depending on the specialty.

So I'm traveling around the country, interviewing at different residency programs, trying to convince people of why I would make a good doctor and a valuable addition to their institution. It's rather intimidating and exhausting, not to mention I've now developed a surprisingly passionate hatred of people who place both of their carry-on items in the overhead compartments on airline flights. However, it has brought about a great deal of introspection regarding my life and what's important to me. One of the things I find myself talking about time and time again is communication, and my interest in writing naturally comes up as an example of practicing my communication skills.

I do want to be a writer as part of my career. The best way to do that is to write as much as I can and read what other people have written. I need to make it a priority. While interviews may be nerve-wracking, the questions I've been asked have helped me remember experiences during medical school that affected me in different ways. I plan to write about these experiences and other random thoughts in the near future. So, stay tuned! I promise I'm not going anywhere this time.