Want to lose weight? Then put down that diet soft drink – new research shows why artificial sweeteners make us crave calorie-laden food.
Researchers from Australia and Austria showed that since the energy associated with sweetness isn’t present in fake sugar, our brain is tricked into building an appetite.
Artificial sweeteners, such as sucralose, are often considered an alternative to sugar to help combat obesity, as well as being used in “sugar-free” sweet drinks and food.
But when the University of Sydney’s Qiao-Ping Wang and colleagues fed fruit flies food spiked with artificial sweetener for more than five days then taken off it again, they found their insect subjects consumed almost a third more calories than they would otherwise.
Would sweeteners have the same effect on mammals, though? To find out, Sydney’s Garvan Institute’s Herbert Herzog replicated the study on mice for seven days – and showed similar results.
This is, they researchers write, because a neural pathway inside the brain’s reward centre that interprets sweetness as energy gets confused.
Study senior author Greg Neely from the University of Sydney says artificial sweeteners trigger a mild starvation response in that neural pathway.
When it senses sweetness but calories are nowhere to be found, the pathway tries to fix the imbalance by telling us to find the energy elsewhere.
And when the flies were taken off the artificial sweetener diet, their mild starvation meant their regular, naturally sweet food tasted 50% sweeter, also prompting them to eat more.
Interestingly, natural sugar had the opposite effect on fruit flies – they ate less food after a diet of five days of extra sugar. But Neely says he’s not sure if this would translate to humans.
For people concerned with their weight, “there’s a wealth of data that suggests a sensible diet plus exercise is the way to lose weight”, Neely says.
“The added thing here is that excessive use of artificial sweeteners might be having adverse effects.
“In animals, that’s certainly the case.”
The study was published in the journal Cell Metabolism.