Put down the artificial sweetener. It’s just making you hungrier.

Researchers at the University of Michigan have found that because artificial sweeteners don’t contain the calories or energy that evolution has trained the brain to expect from sweet-tasting foods, they are doing nothing to satisfy our hunger.

Monica Dus, assistant professor in the U-M Department of Molecular, Cellular, and Developmental Biology, has discovered how the brain of a fruit fly differentiates between the two, and, she believes, human brains will differentiate in the same way.

Fruit flies and humans share about 75 percent of the same disease-causing genes, said Dus, whose findings appear in the journal Neuron.

“We can ask, ‘Do these genes work the same in humans, to tell real sugar from artificial sweetener?'” Dus said. “The bits and pieces are there, so it is really possible that these genes work in a similar way. Plus, we knew that the human brain could tell the difference between real and fake sugar, we just did not know how.”

Dus and colleagues Greg Suh and Jason Lai of New York University School of Medicine withheld food from fruit flies for several hours and then gave them a choice between diet, non-nutritive sweeteners and real sugar. When the flies licked the real sugar, it activated a group of six neurons that released a hormone with receptors in the gut and brain.

The hormone-fueled digestion and allowed the fly to lick more of the nutritious food, but when the fly licked the diet sweetener, it didn’t produce the hormone-digestive reaction because zero-calorie sweetener has no nutritional or energy value.

In every case, the flies abandoned the artificial sweetener and chose the regular sugar because the starved flies needed the energy provided by the calories in the real sugar.

Dus said from an evolutionary perspective, sweet taste means sugar, traditionally from fruit or high concentrate carbohydrates, and a subsequent big energy boost. Fruit flies can’t call out for pizza. Their brains expect calories if they eat something sweet, and that’s why they chose the regular sugar.

If human brains work the same way, Dus said this helps explains why diet foods don’t satiate or satisfy us, and we gain weight while dieting.

“As a society, we try to take short cuts. Low fat and no fat snacks sound like they should be safe and help us to get ready for swimsuit season, but they still have calories that will turn into fat if we eat too much,” said Dr. Brett Blaser, a physician with MountainStar Medical Group. “That usually leads to the consumption of too many calories because our bodies are still craving energy.”

Blaser said by adding back fat, we may add a few more calories, but we will turn off our desire to eat even more in the long run. However, Trans fat and saturated fat are still the enemy, because the body has a difficult time breaking them down. Over time they build up.

“Good fats include poly and mono saturated fat which should be a part of our healthy diets,” he said.