Is Fat the new Thin?

JAMA just published a meta-analysis that the media has been reporting with headlines like "Thin is In, but Fat is Better."  I hate how the media treats meta-analyses as "proof" of something.  To me, a meta-analysis can cue us in on something that needs more study, but not prove that a slightly high BMI offers some sort of protective effect.

The study authors analyzed nearly 100 studies that included more than 2.8 million people. The researchers found that obese people (particularly when BMI was over 35) had a higher all cause incidence of death than normal weight people. However, slightly overweight people (with a BMI of 25 to 30) had a lower risk of dying than people of normal weight.

The idea of body mass index and prediction of mortality risks has been tossed around medicine forever.  It's commonly told to new interns and medical students that thin patients do worse after surgery, for example, than those that are slightly overweight.  I remember being told in rounds that seniors who are slightly overweight live longer than normal weight ones, as if it were a fact.  Intuitively, that makes sense.  If you have extra weight, you have more reserves when you get sick than someone who doesn't.  Oftentimes, thin seniors are malnourished and not physically active.  Those factors lead to increased mortality, and complications.


It's also true that overweight people tend to get more tests and check-ups than thin people.  Even doctors sometimes look at thin people and assume they're healthy, whereas the overweight person would probably get panels of blood tests and an EKG.  That would catch things earlier. The overweight  person with high blood pressure and cholesterol might be on life prolonging-drugs before the normal weight person with the same problems.

JAMA has an interesting commentary about the article that says that it used to be assumed that lifespan was the longest when body weight was maintained at the same level as a 25-year old with similar height and frame size.  Should we compare ourselves to our 25-year old selves?  If you've always been larger, does it confer you with some sort of protective effect?  Are some people's metabolism setup to be healthier at a larger size?  Would losing weight actually increase mortality in some?

I don't think the JAMA article answers any of these questions, but it does question the current dogma that the ultimate goal for our health is to be thin.  What I really think needs to be said is that extremes of anything are bad.  Being "thin" can be just as bad as being "fat" if you take it to extremes.  Exercising too much can be just as bad as not exercising at all.  Eating too little can be just as bad as eating too much.

People make snap judgements based on weight.  That heavy person must sit on their butt all day and eat chips and ice cream.  That thin person must be hitting the gym everyday and living clean.    These assumptions, that thin is fit and fat is not, are not always true.  If only obesity were that easy to cure. Unfortunately, the human body is complex and I don't even think we really understand all the elements that lead to obesity, health and fitness yet.  That slightly overweight person might be the one hitting the gym everyday and eating healthy, whole foods.  The thin one could be living off mountain dew and pop-tarts. You really never know.