For years, researchers have been warning of the costs of trending weight gains around the world. Obesity increases medical costs and decreases quality of life for many people struggling to figure out why their otherwise exemplary discipline falls flat when it comes to maintaining a healthy weight.
Many studies attempt to identify the underlying causes. Is it too many computer games, not enough walk-able spaces, something in our food? Add one more theory to the pile of potential explanations: carbon dioxide activates the hormones that make us hungry.
An alert reader already commented to a report in TreeHugger about the shocking rate at which people all over the world are gaining weight, by pointing out a study that attempted to discover if obesity and diabetes could be correlated with elevated carbon dioxide (CO2) emissions, while controlling for other pollutants such as inhalable particulates (PM).
This CO2-obesity theory is rooted in studies showing that inhalation of CO2 activates neurons responsible for controlling appetite and spurred by the way in which obesity trends have risen as CO2 levels in the atmosphere are rising. A study of carbon dioxide and obesity in Nature went so far as to note that rising obesity has been observed in animal species, presumably indicating a common underlying cause -- which is not likely to be overuse of computer monitor time. The article hypothesizes that
"an increased acidic load from atmospheric CO2 may potentially lead to increased appetite and energy intake, and decreased energy expenditure, and thereby contribute to the current obesity epidemic."
They pursued a small study of animals where all factors were controlled while the CO2 level in their breathing air was varied, but the sample was too small to prove conclusive links. Nonetheless, the results were consistent with the theory and the authors urged further study.
The newest study adding to the growing body of evidence analyzed consumption of carbonated beverages, in which carbon dioxide under pressure forms tiny bubbles familiar to consumers of "carbonated sodas." Lab animals were given either carbonated beverage, a de-gassed carbonated beverage, or plain water in a study that followed their growth for over a year. Human volunteers also were tested after drinking bubbly beverages. They conclude
"These results implicate a major role for carbon dioxide gas in soft drinks in inducing weight gain and the onset of obesity via ghrelin release and stimulation of the hunger response in male mammals."
The jury may remain out for some time on the more complex question of whether the CO2 levels in our atmosphere (and don't forget that our indoor air may be higher in CO2 than outdoors) can be linked to the epidemic of obesity, but the door is closing on the question of sodas.
If the sugars or fake sugars don't get you, the bubbles will. It's time to put sodas in the same category as champagne: only for special occasions.