How An Artificial Sweetener Increases Appetite

You can cheat your taste buds with an artificial sweetener, but you can’t cheat your brain. That's the finding from a study on the common sweetener sucralose published Tuesday.

The study could explain the frustrating observation that dieters consuming foods with non-nutritive sweeteners don't find it helps them lose weight.

However, further research is needed to be sure that the findings in animals apply to humans, and if so, whether it applies to other artificial sweeteners.

The Australian researchers said they discovered a brain system in animals that equates sweetness with energy content, and how that system recalibrates when the sweetness comes from sucralose.

Sucralose is a chemical relative of sugar and made from it, but is 600 times as sweet. It is sold directly under brand names including Splenda, Sukrana, SucraPlus, Cukren and Nevella.

It's also an ingredient in such common foods as Hansen’s diet sodas; Swiss Miss Hot Cocoa Mix; Heinz Tomato Ketchup; Reduced Sugar; and Altoids Sugar-Free Smalls.

Sweetness is generally a good guide to energy content in nature. Sugar and honey, for example, contain readily available calories. But sucralose contains no calories. The study found that the brain system detects that lack of energy and adjusts to increase appetite to compensate.

The system is not only present in such widely disparate animals as fruit flies and mice, but involves ancient energy-regulating chemicals such as insulin. These facts indicate the system may also be active in people, the study said.

"Together, our data show that chronic consumption of a sweet/energy imbalanced diet triggers a conserved neuronal fasting response and increases the motivation to eat," the study stated.

Researchers led by Greg Neely from the University of Sydney tested food consumption in fruit flies and mice when given food containing sucralose. Fruit flies were given a diet with sucralose, then switched to a diet without it. Their calorie consumption increased 30 percent due to the increased hunger caused by the recalibrated system.

But when the sweet-sensing system was genetically knocked out in mice, they didn’t increase eating in the presence of sucralose.

In addition, animals given a diet with sucralose tended to be more hyperactive and had trouble sleeping well. This is similar to effects seen in humans.

Dr. Ken Fujioka, a weight-management and metabolic specialist at Scripps Health, said the study was "extremely well done," but limited by its focus on sucralose. In addition, the study didn't demonstrate that consuming more calories caused the animals to gain weight, he said.

Further research is called for to extend these results to people, Fujioka said.

"I'll be honest -- I love diet sodas," Fujioka said.

As a practicing physician, Fujioka said he suggest that people with difficulty controlling their weight can perform their own experiment to see if sucralose makes them hungrier. They can eat foods without sucralose for a week or so, and then eat the same diet including foods with sucralose.

Fujioka said he doubted that effect of sucralose observed in animals can completely explain the response to artificial sweeteners in people. Humans are just too genetically diverse for one mechanism to account for everything, he said.

It's more likely that if the sucralose effect exists in people, it's limited to people who are genetically predisposed, Fujioka said.