The Obesity Paradox: Does being slightly "overweight" decrease mortality risk?

Image courtesy of livelaughlipstick.blogspot.com
Image courtesy of livelaughlipstick.blogspot.com

At AprilAge, we're always on the lookout for new research into any of the areas that the APRIL Face Aging software covers - from smoking, to sun exposure, to weight and obesity.   Health educators know that showing patients how they will age with various lifestyle effects on their appearance can be a compelling factor in health education.    Therefore, a new study (and resulting discussion in the media) about the relationship between weight and mortality risk, involving nearly three million subjects from more than a dozen countries, was recently conducted by Katherine M. Flegal and her associates at the C.D.C. and the National Institutes of Health, recently caught our eye.  The researchers found that all adults categorized as overweight and most of those categorized as obese have a lower mortality risk than so-called normal-weight individuals.

Contrary to expectations, higher all-cause mortality was NOT observed in individuals with BMIs of between 30 and 35, the “obese” range. Furthermore, mortality was significantly LOWER among those who were “overweight” with a BMI of 25 – 30 than those in the normal weight range. These findings remained consistent even after adjusting for smoking status and pre-existing disease.

Writing about the discussion, John LaMattina in Fobes says that Flegal’s paper provides yet another example of what is termed in the medical literature as the “obesity paradox”. While obesity is a major risk factor for heart disease as well as other diseases like diabetes and even cancer, obese patients seem to have a survival benefit in certain situations. How can this be? An editorial in JAMA  rightly points out that BMI is inadequate as a sole predictor of metabolic risk. BMI doesn’t take into account nutritional status, disability and disease; any analysis of overweight and moderately obesity people needs to include a variety of parameters such as blood pressure, lipid levels, fast blood sugar levels and even waist circumference.

Also adding to the Obesity Paradox discussion is Paul Campos, a professor of law at the University of Colorado, Boulder, and the author of “The Obesity Myth: Why America’s Obsession With Weight Is Hazardous to Your Health.”  Writing recently in a New York Times Op-ed, Professor Campos states:  "In reality, of course, it would be nonsensical to tell so-called normal-weight people to try to become heavier to lower their mortality risk. Such advice would ignore the fact that tiny variations in relative risk in observational studies provide no scientific basis for concluding either that those variations are causally related to the variable in question or that this risk would change if the variable were altered.  This is because observational studies merely record statistical correlations: we don’t know to what extent, if any, the slight decrease in mortality risk observed among people defined as overweight or moderately obese is caused by higher weight or by other factors. Similarly, we don’t know whether the small increase in mortality risk observed among very obese people is caused by their weight or by any number of other factors, including lower socioeconomic status, dieting and the weight cycling that accompanies it, social discrimination and stigma, or stress."

All this seems to point to the conclusion that many factors must be considered when assessing mortality risk - BMI is just one.