Those of you who have been reading my blog for a while know that I've occasionally talked about artificial sweeteners, and how all the scientific evidence indicates they are perfectly safe for most people.
Now, when I say safe, I mean safe from a toxicity point of view. These substances aren't going to harm you. They don't cause cancer...they don't cause Parkinson's....they don't cause multiple sclerosis....they don't cause Gulf War syndrome....yada, yada, yada.
However, when it comes to weight gain, that's where things get a bit more tricky. A recent article came out in the Journal of the American Medical Association, discussing evidence that artificial sweeteners may be linked to weight gain. Some of this hoopla was generated over a study done in February. In this study, 8 rats consuming saccharin-sweetened yogurt ate more food overall and put on more weight during a two week period compared to 9 rats consuming sugar-sweetened yogurt. Why? The scientists felt that the artificial sweeteners caused a disconnect between sweet taste and calories. In other words, when the rats ate something sweetened with sugar, the sweetness told their brains they were taking in more calories, which caused the rats to compensate by eating less later. However, when the rats got the artificially-sweetened yogurt, they weren't getting the calories their brains were expecting based on the taste. So, the "sweet feedback" decreased, and the animals didn't regulate their food intake as well.
In a study on humans, researchers found that, although artificial sweeteners and sugar stimulated the same taste buds, they affected the brain differently. Only sugar stimulated the part of the brain that responds to food rewards. This brings about the possibility that artificial sweeteners may not be as satiating as normal sugar.
Does this mean artificial sweeteners will make you fat? Not quite. First, keep in mind that the rat study was a very small study (17 rats isn't very much for an animal study). Also, humans are much more complicated than rats when it comes to regulating food intake.
There are also studies that show the opposite. In one study, rats actually lost weight when they consumed aspartame (Nutrasweet). In a study on humans, people ate less calories when they consumed aspartame-sweetened soda as compared to sugar-sweetened soda (although this was an older study that only lasted 3 weeks). In another 10-week study, people that ate sugar-sweetened foods gained weight, while people who ate artificially sweetened foods did not.
This all probably seems very confusing to you. However, let me make some sense of it. The reason you see all this conflicting information is that people's responses to artificial sweeteners vary. In people who are "sweet sensitive" (i.e., their taste buds are very sensitive to sweetness and they experience sweet taste with more intensity than other people), artificial sweeteners can stimulate appetite. In people who are not sweet-sensitive, artificial sweeteners won't have any effect.
As with many things, moderation is key. Artificial sweeteners in low amounts aren't going to represent a problem for most people who are trying to lose or maintain weight. In fact, they're often necessary to sweeten protein shakes (protein helps suppress appetite, and who wants a bland protein shake?). Just don't go overboard on them. If you start consuming artificially sweetened products all of the time, you might interfere with your brain's "sweet feedback" mechanisms and make it more difficult for your body to regulate appetite.