Artificial sweeteners trick the tongue but not the brain

For more than a century, people have attempted to control weight gain by substituting zero-calorie artificial sweeteners for sugar. Then researchers discovered a perplexing conundrum: Some people who used artificial sweeteners actually gained more weight than people who consumed sugar.

A decade of research could not solve the mystery. But now scientists in Australia have, for the first time, discovered how artificial sweeteners impact the brain’s ability to regulate hunger and increase appetite.

During the study, researchers at the University of Sydney put fruit flies and mice on a five- to seven-day diet containing sucralose, the zero-to-low calorie artificial sweetener marketed as Splenda.

“After chronic exposure to a diet that contained the artificial sweetener sucralose, we saw that animals began eating a lot more,” lead researcher Greg Neely said.

When the researchers studied the brain activity of the fruit flies and mice, they discovered a brain system that senses the sweetness of a food and compares it to the energy level of that substance. Under natural circumstances, a substance high in sweetness is generally also high in calories or energy. The brain recognizes this balance as normal. But when that ratio is out of balance, when sweetness is high but calories are low, the brain tries to correct the sweetness-energy ratio by telling the body it needs more food, Neely said. In other words, the brain responds by stimulating hunger and making food taste better, much as it would in a mild starvation situation.

Researchers also found chronic consumption of sucralose makes natural sugar taste sweeter. So even returning to natural sugar consumption causes the brain to perceive the sweetness-energy ratio as out of balance, again resulting in increased hunger.

In fact, when the researchers switched the fruit flies back to natural sweeteners, they consumed a whopping 30 percent more calories.

The study also revealed other behaviors consistent with mild starvation—hyperactivity, insomnia, and decreased sleep quality—rose with sucralose consumption.

“These findings further reinforce the idea that ‘sugar-free’ varieties of processed food and drink may not be as inert as we anticipated,” researcher Herbert Herzog said.

Scientists began researching artificial sweeteners—and warning about their safety—in 1878 with the discovery of saccharine.

In 1906, Harvey Wiley, chief of the U.S. Department of Agriculture’s chemical division, was so convinced of saccharine’s danger that he took his case to President Theodore Roosevelt. But he couldn’t convince the president, who used saccharine to control his own weight. According to CNN, Roosevelt declared anyone who claimed saccharin was injurious to health “an idiot.”

During World Wars I and II, when sugar was in short supply and scientists had not found any hard evidence of saccharine’s harm, consumer demand skyrocketed.

Then in 1976, a researcher working with a chlorinated sugar compound decided to take a taste. He found it “finger lickin’ good.” Food manufacturers soon began to favor the new compound, sucralose, because it remains stable when heated.

Within 30 years, millions of people were using artificial sweeteners for weight control. But in 2005, researchers at the University of Texas conducted a longitudinal study of 384 participants. They compared the subjects’ diet soda consumption with increases in waist circumference over a period of up to 12 years. The researchers were shocked to find diet soda drinkers had increases in waist circumference nearly triple that of people who did not consume diet soda.

Now researchers may have an explanation for those results.