It’s Real

In my previous post, I described two key limitations of the body mass index (BMI), and this post will continue the discussion with a related topic.  Having mentioned the BMI limitations, I do believe that the BMI is helpful in assessing the population at large.  Through various studies, we’ve learned that the BMI of American adults has increased steadily for several years now – presented here graphically by the CDC.  As I mentioned previously, BMI data are only part of the story, so the trend seen in that CDC map doesn’t by itself necessarily mean that people are getting fatter – it only means that they’re getting heavier.  Theoretically, American adults could be exercising more, eating healthier, and subsequently increasing their lean body mass (i.e. muscle) as they become more fit, which would result in a higher BMI, but a lower body fat percentage.  Overall Physical activity, strength training, and nutritional data tell us though that this isn’t the case, so one can reasonably assume right now that the steady increase in BMI is due to increased body fat.

Now, some critics of the obesity epidemic say that it’s overblown or even non-existant.  Examples include the authors of the books The Obesity Myth and Fat Politics.  Critics decry the legitimacy of the obesity epidemic by pointing to:

• Self-serving interests (e.g. the weight-loss industry, Big Pharma, etc.)
• Questionable definition and diagnostic method (i.e. BMI)
• Exaggerated links between weight gain and health

Are there people and organizations with motive to promote an obesity problem?  Absolutely.  Their existence though only means that data and events should be considered with a critical eye, not dismissed outright.  Is the BMI imperfect?  It is, as I’ve already mentioned.  Considered with other data however, BMI data still reasonably suggest that people are getting larger, and not due to healthy behaviors.  Are the links between health and weight exaggerated?  No, the links aren’t, because research shows correlations between the two.  What’s in dispute is the strength of that relationship – that is, to what extent a person can be overweight before health issues come into play, and whether lifestyle factors can delay those effects (as mentioned in a previous post about the ‘fit but fat’ theory).  However, even if we determine that a little extra weight isn’t problematic and that a person would have to gain quite a bit to experience health problems, we’re clearly headed in that direction as indicated by the CDC map.

So that’s why I say that the BMI can be helpful if used properly, and why I say the obesity epidemic is real.  The point is that when assessing health as it relates to body weight, whether for an individual or the population, we need to recognize the limitations of the measurement tools and look to fill the gaps to get the complete story.