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Artificial Sweeteners Trip Appetite Control Mechanisms

A study published in Cell Metabolism has identified a new system in the brain that senses and integrates the sweetness and energy content of food, and in so doing has explained why artificial sweeteners can make people feel hungry and therefore eat more.

“After chronic exposure to a diet that contained the artificial sweetener sucralose, we saw that animals began eating a lot more,” said lead researcher A/Prof Greg Neely of The University of Sydney. “We found that inside the brain’s reward centres, 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 the study, fruit flies that were exposed to a diet laced with artificial sweetener for more than 5 days consumed 30% more calories when they were subsequently given naturally sweetened food.

“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,” Neely said.

This is the first study to identify how artificial sweeteners can stimulate appetite, with researchers identifying a complex neuronal network that responds to artificially sweetened food by telling the animal it hasn’t eaten enough energy.

“Using this response to artificially sweetened diets, we were able to functionally map a new neuronal network that balances food’s palatability with energy content. The pathway we discovered is part of a conserved starvation response that actually makes nutritious food taste better when you are starving,” Neely said.

The researchers also found that artificial sweeteners promoted hyperactivity, insomnia and decreased sleep quality – behaviours consistent with a mild starvation or fasting state. The effects on sleep have previously been reported in human studies.

To discover whether artificial sweeteners also increased food intake in mammals, Prof Herbert Herzog’s laboratory at the Garvan Institute of Medical Research replicated the fruit fly study in mice. Mice that consumed a sucralose-sweetened diet for 7 days displayed a significant increase in food consumption, and the neuronal pathway involved was the same as in the fruit flies.

“These findings further reinforce the idea that ‘sugar-free’ varieties of processed food and drink may not be as inert as we anticipated,” Herzog said. “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.”