Sep 30, 2010

Obese but Fit?

In a must-read 5-part series over on Obesity Panacea, Peter Janiszewski took a look from a scientific perspective at the question of people who are obese but otherwise fit, to see if they are actually "healthy."

Depending on how strictly you categorize someone as metabolically healthy, 6%-30% of people who are obese fit into this group, which they call "metabolically healthy obese" (which I'll abbreviate as MHO), and either way, I am one of them: My BMI is 34.4. (18-25 would be "normal." 25-30 would merely be "overweight." 40+, "morbidly obese.") Yet, as evidenced by my recent panel of cardiovascular fitness, I am otherwise completely fit and healthy.

In part 1, Dr. Janiszewski introduces the series, describes the phenotype, and gives a few examples. He is quick to point out in this post that MHOs' metabolic profile quickly deteriorates when they stop training, which left me asking if the same is true for their fit counterparts.

In part 2, he cites two studies which conclude that MHO individuals are not at greater risk of developing type 2 diabetes nor having a cardiovascular event than the fit and normal-weight people in the study.
So, not only may 1 in 3 obese individuals have a healthy metabolic profile, but, in fact, their future risk of developing diabetes and cardiovascular disease may be equal to that of healthy, lean individuals.
The bad news starts on part 3, where he interviewed Dr. Jennifer Kuk about a study she published in the journal Diabetes Care. Dr. Kuk and he colleagues, who used very strict standards when categorizing MHOs (and thus found only 6% of obese people were metabolically healthy), found that MHOs die at the same rate as their unfit obese counterparts, even though they're less likely to develop diabetes and heart disease. They reconcile this by pointing out the increased risk of death by cancer (80% of the MHOs who died) and higher likelihood of death due to trauma.

part 4 was downright alarming to me because it discussed a study of 20 women which showed that losing weight actually decreased their insulin sensitivity, increasing their risk of type 2 diabetes! This was in contrast to unhealthy obese women, who had a very significant increase in insulin sensitivity. The study suggested that perhaps doctors should recommend that MHOs not lose weight, but rather be careful not to gain. Dr. Janiszewski was skeptical:
In essence, the idea that healthy obese individuals may not have much to benefit from weight loss, metabolically speaking, is not that surprising – they are healthy to begin with! However, whether weight-loss may actually be ill-advised for healthy obese individuals needs to be investigated by future studies – until a counter-intuitive finding such as this one is corroborated, many remain doubtful (including me).
A cautious sigh of relief came in part 5, where Dr. Janiszewski discussed his own study which he conducted in response to the study presented in part 4. The study, published in the journal Diabetes Care, disagreed with the findings of the previous study - insulin sensitivity was increased by both groups (that is, MHOs and non-metabolically normal obese), though not as much in the MHOs. He attributes this to the ceiling effect:
That is, since they were healthy to begin with – they can only get so much healthier after weight loss.
My thoughts as an MHO
I always knew that I was healthier than friends who are obese and not active. I even suspected that I was at least as healthy as thin unfit friends. But the fact that my risk of developing cardiovascular disease or diabetes was as low as someone in great shape and active? Encouraging. However, that is not the end of the story by any means. The increased weight is a big deal in my performance as a runner - my theoretical best performance is much slower at 300 lbs than it is at 200lbs (which, by the way, would not be underweight for me.) Also, my joints and lower leg muscles would only appreciate having less of a load to carry through 30 or 40 miles per week. Dr. Janiszewski agrees when he concludes:

Given the numerous non-metabolic benefits of weight loss (mobility, joint problems, psychological status, sexual function, etc.), all obese individuals have something to gain from a modest 5-10% weight loss.
steve is taking a break from regularly updating this blog.