Consuming artificial sweeteners can lead to over-eating, and Australian research may have found out why.

A new study sheds light on the effects of artificial sweeteners on the brain’s ability to regulate appetite, and in altering taste perceptions.

Billions of people worldwide consume artificial sweeteners and they are prescribed as a tool to treat obesity, despite little being known until now about their possible mental impacts.

Researchers from the University of Sydney and the Garvan Institute of Medical Research have identified a system in the brain that senses and integrates the sweetness and energy content of food.

“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.

“Through systematic investigation of this effect, 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 prolonged periods (more than five days) were found to consume 30 per cent more calories when they were then given naturally sweetened food.

“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 Associate Professor Neely.

This is the first study to identify the complex neuronal network that responds to artificially sweetened food by telling the animal it has not 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,” A/Prof Neely said.

“The pathway we discovered is part of a conserved starvation response that actually makes nutritious food taste better when you are starving.”

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

To test the effect on mammals, the study was replicated using mice.

Again the mice that consumed a sucralose-sweetened diet for seven 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. 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,” Professor Herbert Herzog.