Research results provide conflicting results as to whether or not diet soda causes weight gain, notes NBC. In a 2015 study published in the Journal of the American Geriatrics Society, researchers found that people who didn't drink diet soda gained 0.8 inches around their waists, while people who consumed diet soda daily gained 3.2 inches, reports Time. In an industry-sponsored 2014 study, people who drank diet soda lost 44 percent more weight than people in the control group, states Healthline.
Scientists who believe that diet soda causes weight gain don't know why it happens, notes Time. They theorize that artificial sweeteners confuse the brain's link between sweetness and calories. Artificial sweeteners also may cause more cravings for sweet treats. Research suggests that artificial sweeteners may affect the gut bacteria and lead to conditions that cause weight gain, such as glucose intolerance and insulin resistance. Other studies indicate that artificial sweeteners may inhibit leptin, which is the hormone that prevents the body from feeling hunger.
Some research suggests that drinking diet soda as part of a diet and exercise plan does not prevent weight loss, according to Healthline. Still, medical professionals caution people who drink diet soda to practice moderation. They also should know that artificial sweeteners may make it easier to overeat, notes Health. If people think of consuming diet drinks as a way to conserve calories, they may overeat in other areas of their lives.