Sweetener scrutiny: Are sugar substitutes a helpful tool or an ineffective crutch?

Artificial sweeteners are considered safe, but questions persist as to what role they play in helping patients lose weight of if, in fact, they cause people to eat more.

By Victoria Stagg Elliott, AMNews staff. April 7, 2008.

The rats in the West Lafayette, Ind., laboratory of Susan Swithers, PhD, don't lose weight when they eat artificially sweetened food. They eat more, and gain more. "Rather than these kind of products making it automatically easier to lose weight, they might make it automatically harder," said Dr. Swithers, a Purdue University associate professor of psychological sciences.

Her study documenting this phenomenon, in the February Behavioral Neuroscience, is the latest flare-up in the decades-long debate regarding the safety of artificial sweeteners and whether they aid weight loss. Cancer fears related to these products may have faded, but the theory they might trigger overeating lives on.

New evidence from some epidemiological studies supports that view. A paper in the Feb. 12 Circulation, for instance, associated drinking one can of diet soda per day with a 34% increased risk of developing metabolic syndrome compared with those who did not drink any carbonated beverages. People who drank the sugar-sweetened versions had a 10% increase in risk.

"I'm wondering if maybe the artificial sweetener makes you feel hungrier somehow," said Lyn Steffen, MPH, PhD, one of the authors and associate professor at the University of Minnesota in Minneapolis. "You drink this artificially sweetened drink, and you might feel satisfied for a short time. At the end of the day, it actually makes you eat more."

It's not clear why artificial sweeteners somehow might make weight gain more likely, but preliminary data suggest that it could be how the brain reacts. A study in the Feb. 15 Neuroimage compared the brain activity of 12 healthy women fed sugar or the artificial sweetener sucralose. Both substances activated areas of the brain associated with pleasant taste, but sugar had a stronger effect in those areas that played a role in expectation and satisfaction. The authors suggest that this finding indicates sugar may turn off the desire for more sweetness, but artificial sweeteners do not. Additional calories are needed to get it to stop.