If you’re trying to kick sugary sodas, some scientists and the Centers for Disease Control and Prevention both recommend swapping them out with a diet soda. After all, the sugar from soda is strongly linked to obesity, type 2 diabetes and dental cavities, while diet soda has no sugar in it at all.
But one strange thing about diet soda is that the people who drink it are actually more likely to have larger waist sizes (a measure of belly fat) than those who drink regular soda. Diet soda drinkers are also more likely to have type 2 diabetes and metabolic syndrome than people who didn’t drink diet soda at all.
At this point, you might suspect that the artificial sweeteners in diet soda are causing drinkers to gain more weight, but these studies don’t demonstrate cause. Instead, they merely show an association between diet soda and poor health that needs further research.
Paul Jacques, director of the Nutritional Epidemiology Program at Tufts University, published a study in 2015 comparing the effects of regular soda and diet soda on fatty liver disease risk (a condition in which fat accumulates in the liver and can cause scarring and inflammation). He found that while regular soda consumption increases one’s risk of the disease, especially in overweight and obese people, diet soda doesn’t. However, he hesitated to recommend diet soda as a better alternative to regular soda.
"We know sugar-sweetened beverages are unhealthy but we don't have evidence showing that artificially sweetened beverages are healthy alternatives,” he wrote in an e-mail to HuffPost.
Mary Story, a child nutrition and obesity expert at Duke who served on the most recent Dietary Guidelines advisory committee, was more confident in doing so. She pointed out that this research does not show that diet soda causes obesity or weight gain, and that the Food and Drug Administration has approved artificial sweeteners for use in food and drink. However, Story wrote in an e-mail to HuffPost that while adults should choose diet soda over regular soda, children should not drink it at all.
Wayne Campbell, a professor of nutrition science at Purdue, said water should be everyone's number one drink choice.
"Water is best, but if sodas are a beverage of choice, diet sodas are preferred for people seeking to control body weight and avoid excess added sugar intake," he said. "There are more nutrient-rich beverages to consume on a daily basis, especially low- or nonfat fluid milk."
Some scientists suspect that artificial sweeteners really do have a cause-and-effect relationship with metabolic issues. Eran Elinav of the Weizmann Institute of Science in Israel published research in 2014 that found artificial sweeteners changed the composition of participants' gut bacteria over time, and that this could be responsible for the participants’ increasing glucose intolerance as they consumed more artificial sweeteners.
But others suspect that diet soda drinkers are more likely to be engaging in a host of other lifestyle choices that could be contributing to weight gain more than the theoretical harm from artificial sweeteners.
A 2015 study found that on the days participants drank diet soda, they were also more likely to eat extra calories from junky snacks like ice cream, pastries and french fries than on the days they drank regular soda. Again, this study doesn’t establish cause and effect, but it does hint at some complex psychological reasons diet soda may affect the food choices we make, said researcher Ruopeng An. Maybe people eat the junk food first, feel guilty and then down a diet soda to make them feel better. Maybe they drink the soda first, and then feel justified in indulging in more high-calorie snacks than they normally would.
For what it’s worth, a study funded by the American Beverage Association and conducted by researchers who also moonlight as consultants for Coca-Cola found that people who are trying to lose weight dropped more pounds if they drank diet soda over water. Take that one with a grain of salt.
Given the CDC’s advice that we should quit regular soda habit with the help of diet soda, it seems that diet drinks are the lesser of two evils -- but no one would call diet soda a “healthy” beverage. And American shopping trends seem to reflect that sentiment.
While 20 percent of Americans drink an artificially sweetened drink on any given day, and about 30 percent of Americans drink at least one sugary drink a day, market data over time shows that more Americans are saying no to soda in all its forms. Sales of both regular and diet soda have been steadily decreasing in the U.S. since at least 2000, reports the Washington Post. As unabashed fans of water, we’ll drink to that news.