One of the perverse pleasures of spending too much time in airports is getting to people watch. I put on my "anthropologist from Mars" glasses and pass the time by staring at strangers, watching what they eat, read and how they struggle to nap in uncomfortable positions. This morning, while waiting on a very delayed plane in the Portland airport, I watched a woman perform yoga by the gate.
But if I really were an anthropologist from Mars I'd be most puzzled by something else that people in airports do: drink lots of diet soda. I write this in the San Francisco airport, where I'm sitting on a bench with five other people, all of whom are sipping some sort of beverage with artificial sweetener in it, from Diet Snapple to Pepsi One.
This is a bizarre ritual, no? We're deliberating duping our tongue, enjoying the illusion of sweetness without the thing that the sweetness is supposed to represent: metabolic energy. What I find most ironic about these diet colas is that there's good evidence that fake sugar actually leads to weight gain. Consider this recent paper in Behavioral Neuroscience, which found that rats fed artificial sweeteners gained more weight than rats fed actual sugar:
Animals may use sweet taste to predict the caloric contents of food. Eating sweet noncaloric substances may degrade this predictive relationship, leading to positive energy balance through increased food intake and/or diminished energy expenditure. Adult male Sprague-Dawley rats were given differential experience with a sweet taste that either predicted increased caloric content (glucose) or did not predict increased calories (saccharin). We found that reducing the correlation between sweet taste and the caloric content of foods using artificial sweeteners in rats resulted in increased caloric intake, increased body weight, and increased adiposity, as well as diminished caloric compensation and blunted thermic responses to sweet-tasting diets. These results suggest that consumption of products containing artificial sweeteners may lead to increased body weight and obesity by interfering with fundamental homeostatic, physiological processes.
There's also some tentative evidence of the same effect in humans:
Splenda is not satisfying--at least according to the brain. A new study found that even when the palate cannot distinguish between the artificial sweetener and sugar, our brain knows the difference.At the University of California, San Diego, 12 women underwent functional MRI while sipping water sweetened with either real sugar (sucrose) or Splenda (sucralose). Sweeteners, real or artificial, bind to and stimulate receptors on the taste buds, which then signal the brain via the cranial nerve. Although both sugar and Splenda initiate the same taste and pleasure pathways in the brain--and the subjects could not tell the solutions apart--the sugar activated pleasure-related brain regions more extensively than the Splenda did. In particular, "the real thing, the sugar, elicits a much greater response in the insula," says the study's lead author, psych ia trist Guido Frank, now at the Univer sity of Colorado at Denver. The insula, involved with taste, also plays a role in enjoyment by connecting regions in the reward system that encode the sensation of pleasantness.
The essential lesson is that the brain doesn't like being tricked. When you give us sweetness without the caloric energy, we end up craving calories more than ever.
Brain & Behavior
Comments (51)
I quit drinking soda when my brand changed their recipe (without publicity). Months later I began to notice the sweet taste of carrots, peas, lima beans, cauliflower, broccoli, whole-grain bread, and meat.
Posted by: 6EQUJ5 | February 11, 2009 6:06 PM