Swapped sugar for stevia, but not losing weight? Blame your brain.
It's long been known artificial sweeteners make you hungry, but now scientists know why - they make the real thing taste so much better.
"Inside the brain's reward centres, sweet sensation is integrated with energy content," says Associate Professor Greg Neely from the University of Sydney. "When sweetness versus energy is out of balance for a period of time, the brain recalibrates and increases total calories consumed."
It does this by increasing the "sweet intensity of real nutritive sugar", giving animals - including people, presumably - more incentive to eat sugary food.
"We were able to functionally map a new neuronal network that balances food's palatability with energy content," says Prof Neely.
"The pathway we discovered is part of a conserved starvation response that actually makes nutritious food taste better when you are starving."
The research, published in journal Cell Metabolism, also found a link between the consumption of artificial sweeteners and hyperactivity, insomnia and poor sleep quality, all behaviours consistent with "a mild starvation or fasting state".
The initial testing was done on fruit flies, and replicated on mice.
"These findings further reinforce the idea that 'sugar-free' varieties of processed food and drink may not be as inert as we anticipated," says Prof Herbert Herzog of the Garvan Institute of Medical Research.
"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."