Since I'm prepping a Research Methods course right now and putting together a unit on how inconsistent measurement fucks science up: this is your regular reminder that the obesity epidemic is not real. (short thread)
The NIH changed the BMI cutoffs arbitrarily in the late 90's, re-categorizing millions of people as overweight and obese overnight. This created the illusion that the average body size was increasing at an unprecedented rate.
Essentially, the NIH noticed that body size and heart health were *correlated*, and decided that labeling more people overweight/obese might somehow *cause* a reduction in heart disease.
You can see that this move required several logical jumps. 1. Assuming that just because body size is correlated with heart disease, that body size *causes* heart disease; 2. Assuming that labeling a person as overweight/obese would *cause* them to lose weight....
3. Assuming that losing weight would reduce the risk of heart disease (the research is actually mixed on this), and 4. Assuming that losing weight is a sustainable solution to health complaints associated with a large body size
We don't have good empirical support for any of these logical jumps. We know that a large body size and heart disease are associated, but we don't know that one causes the other, or that long-term weight loss is either a) possible for most people, or b) solves the heart disease
(It may be that both having a high BMI and having heart disease are caused by a third, separate factor and that attempts at addressing one of those things has no bearing on the other, for example).
Here's a source on all this btw: cnn.com/HEALTH/9806/17…
And here for a nice, approachable review of the flaws with the science on this: freakonomics.com/podcast/freako…
Anyway, by reclassifying tons of people as overweight and obese, the NIH manufactured a health crisis. And we've been dealing with the resultant freakout since uhhh 1998 when they made this move.
Always remember that when it *looks* like a group is growing, it may just be that we're identifying them differently from how we used to. See also: increased identification of Autism being mistaken for an increase in Autism.
Another example: increased acceptance and out-ness of trans people being mistaken for transness being a trend.
