BMI Blues

The Death Knell of a Diet Diagnostic

We get all excited when we hit on something that (we think, we hope, we pray) will give us an objective measure we can point to on a chart and say, “You see here, this says you’re going to have x, y, or z.” In fact, making our decisions objective and quantifiable is one of the goals of the scientific process.

But in diet and nutrition, this is very difficult. We tried calorie counting, carb counting, fat gram counting and every other variant to plug into an equation that equals low weight and healthy lives. The obesity diabetes heart disease metabolic-syndrome mess we’re in right now doesn’t speak well for these strategies.

Another testament to their failure is the repeat business that new objective measures get. After all, if our current strategies were working, why would we glom onto the latest greatest new tool in the toolbox, which hopes to finally make a dent in the obesity epidemic.

We saw the “glycemic index” arrive in the intoxicating flurry of the Atkins Revolution. The GI is the number that should tell you how much your foods will spike blood sugar and stimulate an insulin response.

You know what they say, “When you have a hammer, everything looks like a nail.” Ture to form, the GI spawned scads of diet approaches along with actuarial tables of foods paired with numbers representing their GI values. This worked very well for diet books, and very poorly as a diet because it actually can help in the short term but typically fails in the long term.

The bloom faded from the GI rose and, although you still see the cling-ons hangers on, this tool is not the end-all it was touted to be. The reason is that the GI of your food (remember all those tables you had to consult?) varied depending on what you ate it with. A banana with peanut butter was not the same as a banana eaten alone, for example.

In any case, with obesity roiling, and clinicians a bit queasy about telling overweight people that they’re overweight without the protective shield of an objective number to hide behind, they turned to another shiny tool: Body Mass Index.

And, as it stands now, BMI is really the only objective “number” we have to measure overweight/obesity, and has been latched onto so strongly that several tipsy individuals have even proposed to apply this measure (a ratio of height to weight) to every school child.

The BMI value, however, is totally flawed. Because it only measures weight (and muscle weighs more per volume than fat), a muscular person who is completely fit will be called overweight or even obese. This makes BMI a ballpark rough estimate guestimation of something you can already see with your own eyes – this person is either overweight or not.

In fact, researchers at the Mayo Clinic just published a paper showing that the BMI tool should be shelved completely. Their results, which just appeared in the journal Lancet, showed that patients with a low BMI had a one-third higher risk of dying and dying of cardiovascular disease. Overweight patients had the lowest risk of dying in general and from cardiovascular causes as well. Obese patients had no increased risk at all.

It’s time to go shopping for another tool.

Alternatively, we could just default our humanity, our instincts, our gut. Crazy idea, I know. But what would it be like if you went into a doctor (this is a science fiction scenario a al George Lucas, so hang on to your light sabers) and you were a person rather than a chart of BMI values? What if you went in and the physician was charged with looking at you to see how you were, not how your data point filled out the pie chart?

In the second scenario, an overweight person and an athlete with the very same BMI value, who both saw the doctor, would both get meaningful responses. The doc would look at each and immediately know that one was obese and the other was not. It’s not objective, but who cares? It is more accurate.

So maybe the solution is less number crunching and more humanity in diagnosis; less glycemic index and more common wisdom; less BMI charts and more straight talking advice. After all, which of these would you rather hear (and which would be more effective for you)?

1. “Your BMI places you in the 73rd percentile of caucasians of your age range within your demographic, indicating that you might possibly need to alter the glycemic index range of your diet, depending on your particular build and muscular profile.”

versus

2. “Looks like you’re getting a little heavy in the middle. Pull back on your portions at the plate. Instead of snacking on Ho Hos and Jolly Ranchers between meals, have some water or some unsalted nuts once in a while. Try that and let me know how you’re doing next time.”

When we go shopping for that new diagnostic tool we desperately need, let’s start with the instincts and humanity of the physicians themselves. That is a tool we can all use in the long term.