We know about artificial sweeteners causing cancer, but a new meta analysis of more than 20 recent studies links aspartame, saccharin, and sucralose to two diseases the sugar substitutes are supposed to help prevent: obesity and type 2 diabetes. In her analysis, Susan Swithers, a professor of psychological sciences and a behavioral neuroscientist at Purdue University, found that using artificial sweeteners as an alternative to a more holistic diet with exercise can be a major health hazard. For instance, a San Antonio heart study, which followed 3,600 adults for eight years, found that sedentary people who consumed one or more diet sodas per day had a 50 percent higher risk of becoming overweight or obese. Another two-year study of adolescents found artificial sweetener consumption was associated with increase body mass index and body fat percentage. Yet another study showed consuming diet soda doubled the risk of metabolic syndrome, a basket of symptoms linked to diabetes and cardiovascular disease. And other studies showed a link between drinking two diet sodas a day and a significantly elevated risk of heart disease.

What's going on here? Swithers says there is evidence that artificial sweeteners can interfere with how the body normally responds to the arrival of something sweet, like release hormones that help control food intake and blood sugar. "When someone eats or drinks real sugars [after regularly consuming artificial sweeteners], the body does not produce the same physiological responses it ought to," says Swithers. "Over the long run, this can lead to overeating, weight gain, and other health outcomes like diabetes, heart disease and stroke," she says.

According to Swithers, there is a silver lining here: People who use artificial sweeteners, exercise regularly, and follow a healthy diet usually consume fewer calories and lose more weight.