Friday, July 31, 2009

More on Megan McArdle's War on a Healthy Diet and Exercise

I have to admit I'm in a bad mood this morning for unrelated reasons, but Megan McArdle's glib misstatements of reality are getting a little irritating:
You can find the same results yourself by reading any study of weight loss: outside of gastric bypass surgery, no system has ever produced any significant long-term weight loss. None. As Paul remarked to me once, "We've run this experiment approximately 220 million times and the result is always the same. Why can't anyone believe it?"
Why won't anyone believe it? Because it's demonstatably untrue, and she and Paul Campos need to stop saying it. Here is a meta-analysis(a statistical combination of many studies - so like a more rigorous review article) from which I will quote:
Although weight regain prevention remains a challenge, there is room for optimism; a nationally representative survey estimates that 20% of individuals attempting weight loss are able to achieve and maintain 5% weight reductions for at least 1 year.[McGuire et al]. Among successful weight losers, various studies indicate that more than 60, 35, and 19% of individuals are able to maintain 10% weight reductions for 1, 3, and 5 years, respectively.[Weiss et al, Lowe et al, Wadden et al]
I can only guess she means "significant" in the non-statistical sense, i.e. that she has some conception of what "real" weight loss is, and these studies just don't measure up. She appears to be of the opinion that losing 10 or 20 pounds and a couple inches off your waist is meaningless, so that's probably what she means... but once again have a proponent of the idea of an "Obesity Myth" stating things in a misleading way. Why not actually state what you mean? Why use such a loaded term as "significant" in such a careless way?

This is what happens when people play advocate for an idea instead of trying to get at underlying truth and have a productive discussion. There are interesting and valid points that have been made by McArdle/Campos, but they are being completely lost because of the pair's apparent attempt to "Win the Internet".