By Jordana Bieze Foster, Editor
It’s hard to remember sometimes that being thin was once undesirable, a sign of poverty, poor nutrition, and low social status. These days, Hollywood-style thinness is associated with wealth—the kind of wealth that might buy the services of a personal dietitian, personal chef, and personal trainer.
Too often, thinness is also equated with healthiness, even by health care practitioners who should know better.
To be sure, the medical consequences of obesity are very real, affecting the lower extremity as well as the rest of the body. But obesity has become so prominent in practitioners’ consciousness that they might fail to recognize that a thin person can also be at risk for osteoarthritis or type 2 diabetes.
I’m no better. A biomechanics researcher who would not be considered obese by any measure recently mentioned in passing that he has type 2 diabetes, and my immediate reaction was one of utter disbelief. Really? But you’re so fit!
Not long thereafter, I came across a recent study in Nature Genetics that found some individuals are genetically predisposed to heart disease and diabetes in spite of also being predisposed to low levels of body fat. These diseases in such patients tend to be more severe when finally diagnosed after years of poor diet, lack of exercise, and other risk factors have been overlooked because the patients appeared to be so healthy.
What isn’t discussed much in the health care community is that individuals with low body weight have their own unique vulnerabilities. Very thin people are far more likely than others to
be anemic or infertile. They have higher rates of osteoporosis and lower extremity stress fractures.
A 2010 study on U. S. Air Force recruits published in the American Journal of Preventive Medicine found that both low and high body mass indices (BMI) were associated with an increased risk of basic training injuries in men. That study found that only high BMI was associated with injury risk in women, but previous basic training studies have found low BMI to be a risk factor in female recruits too.
And at the 2011 annual meeting of the American Podiatric Medical Association, researchers presented data from the Framingham Foot Study suggesting that a high BMI is actually protective against hallux valgus (see “Handicapping hallux valgus”). This seems to be consistent with my personal experience; everyone I know who has hallux valgus is definitely on the low end of the BMI spectrum. I guess that’s not a coincidence, now that I think about it.
But I hadn’t thought about it. And I’d be willing to bet a lot of lower extremity practitioners haven’t thought about it either. That’s the point.
Obesity is a significant risk factor for a number of conditions, and that shouldn’t be ignored. But being thin shouldn’t automatically warrant a clean bill of health either. All patients deserve a thorough history and physical examination, regardless of what they weigh. Because the risk factors that aren’t visible might end up being even more significant than the ones that are.