April 10, 2013

Does #altitude ameliorate #obesity? Color me skeptical

Theoretically, one might think that it would.

The exertion of working in oxygen-lessened air might cause people to burn more calories. Or, the fact that thinner air is less insulating, and it's generally cooler at higher elevations, might cause people to burn more calories to maintain constant body temperature.

That's why, why friend Leo Lincourt posted this link from the Public Library of Science, with the map image at top included, I was intrigued.

And skeptical.

Very skeptical. 

First, there's a lot of Mormons in high-altitude areas of the West. And, per a response on the PLoS page by the author, he admits that, while the study allowed for some demographics, it did NOT allow for religion. Given strong Mormon dietary strictures, including no drinking of alcohol with its "empty" calories, that seems like a pretty serious omission.

As I posted at the PLoS site, the only relatively easy way to determine whether it's likely that Mormonism is at least as causal as altitude or not is to compare obesity in high-altitude areas worldwide versus neighboring flatland areas, i.e., Himalayas vs Asia, Alps vs Europe and Andes vs South America.

I'll be skeptical until I see such research.

Second, the altitude-obesity correlation isn't very strong outside the Rockies.

It looks decent but not fantastic in the Sierras. It appears almost nonexistent in the Cascades.

Third, has this research been "normalized" to allow for larger margins of error in sparsely populated high-elevation counties? I don't know.

Fourth, don't these relatively numerous lower-obesity counties in flatland Florida, flatland New England and New Jersey, and lowland east Texas and coastal California, also undermine any obesity-altitude correlation claims. 

The study author does say that hypoxia is demonstrated as a cause of anorexia and weight loss. He doesn't say how much weight loss it causes. Nor does he say whether this is short-term laboratory-induced hypoxia, or what.

After all, we know that, speaking of the Andes and Himalayas, in the two highest-altitude areas of our world, long term residents, the Inca and Tibetans, actually have their bodies adjust to bind oxygen to hemoglobin more efficiently, or otherwise use oxygen better. Now, in more transient American society, such effects might not "take" for several years. So, obesity as a weight-loss aid might only be of shorter-term benefit.

Jamieson also doesn't say how much less oxygen is needed for the effect. This study mentions an Austrian study that used 1,700 meters, or about 5,500 feet, as a "baseline" altitude for noticeable benefits from hypoxia. In that case, almost all the Mountain States ... just about all of Colorado, Utah and Wyoming, most of Montana, much of New Mexico and Arizona, and a fair portion of Idaho ... should have no darker shading than the medium orange, third level of obesity, if there's much strength to the correlation. However, the map shows MASSIVE variations in those states.

Beyond that, failure to control for Mormonism in the US West, in this study, is questionable.

And, that Austrian study was of only 22 people, and for only three weeks.

Update, April 12: There's more reason to disbelieve these claims. Turns out "fat Southerners" are just more honest about their weight than other parts of the country, often. The Northern High Plains states are the biggest weight liars, and the Southeast among the mildest, research shows.

Here's the money quote on a possible "why," too:
"It is hard to know exactly what is going on, but my speculation is that people in the South are telling the truth more," (biostatistician George) Howard said. "Perhaps there is not as much stigma connected to obesity as say someone in California, or in this case, Minnesota."
Sounds plausible, at least. And, that white area in western Colorado? Ski resort heartland. Think rich, white, Volvo-driving, latte-sipping neoliberal narcissists.

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