How diet soda makes you fat

It has zero calories so it has to be okay for you, right?  Well maybe not so much.

Jonah Lehrer takes a look at a few recent studies that suggest our brains do not like to be tricked by artificial sweetner.  A Behavioral Neuroscience paper found that rats actually gained weight from a diet of artificial sweetners.

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.

Fine they’re just rats, you’re saying, except that the same thing has been found to effect humans. The evidence is certainly there.

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.

Lehrer concludes thus: “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.”

I’ve never been much of a soda drinker and detest diet soda (can’t stand the taste of fake sugars like Splenda, et al. they make my taste buds recoil in horror), but it’s fascinating that our brains will compensate by forcing our bodies to make up for the caloric deficiencies in other ways.

It should be noted that there is evidence that diet sodas do in fact aid in weight control, or have no effect on the body/brain.

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