How Artificial Sweetness MessYour Brain

Artificial sweeteners have been the subject of a lot of scientific debate in recent years, partly owing to the fact that they don’t seem to help much with weight loss at all. In fact, they may actually contribute to weight gain: A study a couple of years ago suggested that they may do this in part by altering the friendly bacteria in our guts, and triggering glucose intolerance.
Though this is likely part of the explanation, a new study finds another way in which they may mess with our bodies–this time through our brains. At least if you’re a fruit fly or a mouse. But the thought is that a similar phenomenon is probably happening in humans.
In the new study, out of the University of Sydney and published in Cell Metabolism, researchers gave fruit flies a diet sweetened either with sugar or with sucralose. When the intake was prolonged (meaning for more than five days at a stretch), the fruit flies ate 30% more calories when their food was artificially sweetened than when it was naturally sweetened.

And when the researchers gave the two groups of mice real sugar later on, they saw differences in how their brains responded, the sucralose-habituated mice having more activity in their brains in response to the real sugar. Which suggests that the sugar may have tasted sweeter after the animal had acclimated to artificial sweetener.
“After chronic exposure to a diet that contained the artificial sweetener sucralose, we saw that animals began eating a lot more,” said study author Greg Neely. “Through systematic investigation of this effect, we found that inside the brain’s reward centers, sweet sensation is integrated with energy content. When sweetness versus energy is out of balance for a period of time, the brain recalibrates and increases total calories consumed.”
In other words, when the brain perceives sweetness without calories–the two go together in natural foods–it flips out a little and recalibrates to the strange balance, or imbalance, it’s gotten used to. “The pathway we discovered is part of a conserved starvation response that actually makes nutritious food taste better when you are starving,” says Neely. The flies also exhibited other “symptoms,” like hyperactivity, insomnia and glucose intolerance.

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