Forget BMI. Do You Know Your 'Best Weight'?

Health is so much more than a number on the scale.

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When it comes to weight, we physicians seem to be woefully bad at addressing the individual sitting in front of us. A typical scenario goes something like this: Overweight patient comes in; doctor consults either an "ideal weight" table or the body mass index (BMI) chart, which reports weight as a function of height and suggests there's only a narrow "healthy range." Doctor comes up with a ridiculously low number for that patient to "aim" for, and infers—or explicitly states—that if the patient doesn't reach that goal, his or her weight will remain unhealthy.

Unfortunately, that practice flies in the face of two incredibly important things—the first being medical evidence. There is no shortage of papers reporting that healthy living—through regular exercise and nutritious eating—provides truly dramatic protection against the risks most commonly associated with weight, even for folks whose BMIs put them well into the realm of medical obesity. Getting just 30 minutes of daily exercise most days of the week, and eating a plant-inclusive, minimally processed diet will confer more benefit to folks at any weight than any medication ever could.

The second is the idea that you need to be at (or very near to) some specific, ideal weight to be considered healthy, which is what those favored charts imply. Consider the analogy of school. While it's true that getting good grades likely does somewhat correlate with future success, does that mean that if you're not in the top of your class you're doomed? Other factors—like your work ethic, your ability to work with others, your persistence, your having tried your best—are as important, if not more important, to future success than grades.

So why do we place such a premium on the notion of that perfect, healthy weight? Why isn't "trying our best" enough when it comes to weight loss? A brief review of the history of dieting suggests that our personal best has never been enough. We seem bent on bouncing from dietary extreme to dietary extreme, serially adopting—and ditching—truly traumatic diets. We aim to suffer and sacrifice and restrict far beyond what's comfortable, and then try to convince ourselves that somehow results won by under-eating and over-exercising will last—that, "nothing tastes as good as thin feels." But of course extremes don't last. As a species, we're simply not built to endure unnecessary suffering for the long haul. And yet each year spawns a new crop of books claiming to have found the latest, greatest (and, of course, highly restrictive) route to weight loss.

Well here are two long-term weight management truisms for you. If you can't happily eat less, you're not going to eat less. And if you can't happily exercise more, you're not going to exercise more. Next time you're considering a new diet or other weight-loss technique, ask yourself a simple question: "Could I happily continue living this way?" If the answer is no, you're just wasting your time. Ultimately, weight lost through suffering almost always finds its way back. You need to like your life.

If you truly want to improve your health, don't aim for perfection. Aim for what I like to call your "best weight." Never forget that your personal best, even when it comes to weight, is always great. Don't let anyone, any chart or any doctor, ever tell you differently.

Corrected on 9/13/2012: An earlier version of this piece made mention of a plant-based diet, when the author intended it to read plant-inclusive.

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Yoni Freedhoff, MD, is an assistant professor of family medicine at the University of Ottawa, where he's the founder and medical director of the Bariatric Medical Institute—dedicated to non-surgical weight management since 2004. Dr. Freedhoff sounds off daily on his award-winning blog, Weighty Matters, and is also easily reachable on Twitter. Dr. Freedhoff's latest book Why Diets Fail and How to Make Yours Work will be published by Simon & Schuster's Free Press in April 2013.