Weight Watchers: Hold the CO2

By Jonathan Marshall

A surprising new academic study finds that today’s young adults—or Millenials—are less interested in the environment than their parents’ generation, even though they stand to inherit a planet that is undergoing rapid and dangerous climate change.

If the specter of mega-storms, extreme droughts, surging sea levels, and acidified oceans doesn’t move them to action, perhaps this news will: Rising levels of carbon dioxide in the atmosphere may contribute not only to global warming but to the global obesity epidemic.

At least that’s a new theory announced by Danish researchers at the University of Copenhagen.

It’s not as crazy as it sounds at first. Apparently CO2 levels may affect levels of the brain hormones, known as orexins, that regulate our metabolism and stimulate our desire to consume food. As we inhale higher levels of CO2 in the atmosphere, our blood may become more acidic (like the oceans), which in turn affects the activity of orexins and makes us hungrier for food.

A small-scale experiment at the university’s nutrition department found that young men exposed for several hours to elevated levels of CO2 ate 6 percent more food than a control group with normal levels of the greenhouse gas.

A similar but uncontrolled experiment has been going on for decades on a global level. Levels of CO2 in the atmosphere have been rising since the industrial revolution, with the widespread burning of fossil fuels. In just the four decades since 1970, the level of CO2 has jumped from 325 parts per million to 390 parts per million, a 20 percent increase.

“This could give us an explanation for why the entire population on this planet is increasing in body weight,” said Arne Astrup, head of the department of obesity and nutrition at the University of Copenhagen. It would explain why even thin people are getting fatter over time, as are many laboratory animals with controlled diets—not just junk-food-eating humans.

Then again, it could all prove to be a spurious correlation. That’s something few serious scientists say any longer about CO2 and global temperature trends, however. The British government’s meteorological office has just confirmed that 2010 was the hottest year on record, and that 10 of the warmest years ever occurred over the past 14 years.

It’s much too soon to tell what 2012 will bring, but temperatures this month in South Dakota hit 94 degrees and Chicago just experienced an unprecedented five straight days over 80 degrees.

If ice cream sales are soaring and waistlines are bulging as a result, one way or another you can blame too much CO2.

Email Jonathan Marshall at jonathan.marshall@pge.com.




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