Only Fat People Drink Diet Sodas, Right?

"Does Diet Soda Make You Fat?" in the Hungry Beast addresses this very question, and, sigh, comes up with a deeply equivocal answer. The results of two studies that author Susan B. Roberts calls "the best out there" are as follows: "In one five-week study conducted in 2008, 27 rats that were provided with a saccharin-sweetened yogurt ate more total food and gained more weight than rats fed sugar-sweetened yogurt. And it wasn’t because they loved the saccharin-sweetened yogurt—in fact, they tended to eat less of it, but went back to their regular chow for second helpings more often than the rats given sugar. On the other hand, a 2004 study of 24 French men and women, also for about five weeks, found that the individuals randomly assigned to include high-calorie, sugar-sweetened beverages in their diet did the most overeating—and had no better hunger control compared to a similar group allocated to consume artificially sweetened beverages."

So since they taste like sweetened rat urine, what on earth is the point of drinking diet sodas? Roberts has thoughts on that, too: "magnetic resonance imaging studies tracking the brain’s responses to sugar and intense sweeteners show that in our unconscious brain we know they are different—even while we perceive both of them as 'sweet-tasting' in our conscious brain. While this might seem like bad news, I view this as positive because it means we can still enjoy sweet taste without getting the neurological high that accompanies a rush of sugar calories."

So you enjoy what you're drinking, but you don't get a buzz. Roberts theorizes that over time we can retrain our brains to uncouple the connection between sugar and the dopamine rush we get from it: "In other words, using artificial sweeteners may actually make us like the real thing less over time, and provide a bridge to a healthier low-calorie, low-sugar diet that still tastes sweet due to our increased sensitivity for the sugars in natural foods."

Interesting. It is true that if you eat something super-sweet and then something not-so-sweet, the less-sweet item tastes almost sour in comparison. I had this happen just this morning, when I had a bowl of Fruity Pebbles (they are much less tasty than I remember from childhood!) and then ate some exceedingly ripe and delicious cantaloupe. The first bite of the melon was horrible. Only on bites two and three did the melon's sweetness emerge. Why is that? Your tastebuds get ... confused? I know it's different from the orange juice and toothpaste effect, but what causes it?

Image source: Flickr member wheany under Creative Commons