SYDNEY, July 13 (UPI) -- Although artificial sweeteners provide the taste people expect from foods, the sugar replacement chemicals also make the brain increase hunger because it thinks not enough food has been consumed for energy.
Researchers at the University of Sydney fed fruit flies and mice a diet including sucralose, and found it throws off the brain's reward centers, as they consumed far more calories than they needed.
While reducing sugar consumption is often regarded as a healthy move in any diet, previous studies have questioned whether replacing real sugar in foods with chemical alternatives is good for health, calling it "counter-intuitive."
Researchers in the new study say, however, that while reduction of sugar consumption can be healthy -- so replacing real sugar with something else should be beneficial -- the effects of using chemicals in unhealthy foods rather than replacing sugar-sweetened foods with those carrying natural sugar had not previously been explored.
"These findings further reinforce the idea that 'sugar-free' varieties of processed food and drink may not be as inert as we anticipated," Herbert Herzog, a professor at the Garvan Institute of Medical Research, said in a press release. "Artificial sweeteners can actually change how animals perceive the sweetness of their food, with a discrepancy between sweetness and energy levels prompting an increase in caloric consumption."
For the study, published in the journal Cell Metabolism, researchers first fed fruit flies a diet laced with the artificial sweetener sucralose, finding the insects ate 30 percent more calories than when they ate naturally sweetened food.
The experiment was then repeated with mice, which were fed a sucralose-sweetened diet for seven days. As with the flies, researchers report the rodents consumed significantly more food than they needed or would have eaten when given naturally sweetened food.
The researchers found sucralose activated a neuronal pathway in the brains of both flies and mice associated with starvation, an evaluation buttressed by the observation of starvation-associated behaviors such as hyperactivity, insomnia and decreased sleep quality in both experiments.
"When we investigated why animals were eating more even though they had enough calories, we found that chronic consumption of this artificial sweetener actually increases the sweet intensity of real nutritive sugar, and this then increases the animal's overall motivation to eat more food," said Greg Neely, an associate professor of science at the University of Sydney.