Researchers are divided over whether diet soda helps people lose weight. Swapping sugary drinks for diet drinks may condition the body to expect calories, which makes people feel hungrier. “Normally, things that taste sweet are followed by sugar and calories,” Susan Swithers, a professor of psychological sciences and a behavioral neuroscientist at Purdue University in West Lafayette, Ind. who has reviewed studies on diet soda . “But the body produces physiological responses — increasing metabolism and releasing hormones — to anticipate the arrival of sugar and calories,” she says.

That, Swithers says, can become a problem for diet soda fanatics. Diet drinks interfere with this “predictable relationship,” meaning the body can’t predict the calorie intake when real sugars are consumed. “Physiological responses become blunted,” she says, and that may lead to a host of other problems too. “The loss of these responses could contribute to excess food intake, weight gain, high blood pressure and over time outcomes like diabetes and cardiovascular disease,” Swithers says. In fact, she says Bloomberg’s soda ban should have been extended to artificially sweetened drinks too.

In one study, individuals who consumed more than three artificially sweetened drinks a day experienced a doubling of their incidence of overweight/obesity over the next 7 to 8 years, compared with those who had consumed none, according to a study published in the August 2008 edition of “ Obesity .” “The more they drank them, the more their waist circumference increased,” says Sharon Fowler, the primary author of the study and specialist in the department of medicine at The University of Texas Health Science Center at San Antonio.

While these results show an association or correlation rather than causation, Fowler says there may be physiological and psychological issues at play. One theory: Drinking artificial sweeteners may cause the body to store more calories in fat cells and also induce hunger, she says. “Studies have shown if animals are fed artificial sweeteners they gain more weight and have more disruption than metabolic imbalance,” she says. “No calories and no consequences is very naive. Diet soda consumption in the U.S. is a major uncontrolled experiment.” She says Bloomberg naively targeted only sugary drinks. Continue reading