Why artificial sweeteners can increase appetite

As well as promoting hyperactivity and insomnia, a new study co-led by the University of Sydney has found that artificial sweeteners actually increase feelings of hunger leading to higher calorific intake.

This is not the first time a link between artificial sweeteners and increased hunger has been suggested, but this new research has identified the brain system that regulates response to sweetness in both insects and mammals.

The first phase of the research was conducted at the Charles Perkins Centre at the University of Sydney. Researchers laced the diet of fruit flies with artificial sweetener and found that after prolonged exposure they consumed 30% more calories when their natural diet was reintroduced.

University of Sydney’s Associate Professor Greg Neely stated: “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.”

The researchers determined that the brain’s reward centre recalibrates the perceived ratio of energy content to sweet sensation when the sweetness to energy ratio is out of balance for prolonged periods.

Professor Neely said: “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.”

The second phase of the study was designed to determine if the neuronal pathways observed in fruit flies are also relevant to mammals. Professor Herbert Herzog’s team at the Garvan Institute of Medical Research exposed mice to a sucralose-sweetened diet for seven days. The mice displayed remarkably similar results to the fruit flies, confirming the same neuronal pathway was involved in regulating overall calorie intake.

Professor Herzog said: “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.”

This research was published in the journal Cell Metabolism.