Do diet sodas cause weight gain?

Dear Dietitian,

I am on a diet and I usually drink one or two diet sodas a day. A coworker insists that diet sodas cause weight gain instead of weight loss. Is this true?


Dear Suzanne,

Artificial sweeteners, or nonnutritive sweeteners, made a debut with saccharin in 1884 in Germany. Saccharin was sold in the U.S. under the brand name Sweet’ N Low. Today there are numerous NNS on the market, some of which are aspartame (NutraSweet and Equal), sucralose (Splenda) and Stevia.

Most NNS are consumed in diet sodas in the U.S., with Diet Coke being the number one selling sugar-free soft drink. Artificially sweetened beverages and foods have allowed diabetics and dieters to enjoy sweetness without the calories, but do they help you lose weight?

Studies are mixed when it comes to artificial sweeteners and weight loss. In a randomized trial, 303 overweight participants were assigned to drink 24 ounces of either water or artificially sweetened beverages. Both groups were on a weight loss plan. At the end of three months, those who consumed the artificially-sweetened drinks lost more weight (13 pounds) than those who drank water (9 pounds). The increase in weight loss is attributed to the opportunity to satisfy a sweet tooth with something that has no calories. It is important to point out that the American Beverage Association funded this study. When a particular group funds research on its product, there is a risk of bias in favor of the product. However, other studies have produced results similar to this one.

There is some concern that NNS lead to weight gain. An eight-year study found a strong link between people who use artificially-sweetened beverages and weight gain. Those who drank the most diet soft drinks gained the most weight. This study was observational, which does not prove cause and effect. It’s also important to note that most people who drank diet soda were overweight at the beginning of the study compared to those who didn’t use artificial sweeteners. They also identified themselves as dieters and long-term weight gain is associated with chronic dieting.

There is one case in which using NNS is ineffective and will likely lead to weight gain. Some people think they are saving calories by drinking a diet soda, so they allow themselves a chocolate bar for an afternoon snack. While an occasional chocolate bar is harmless, fresh fruit and low-sugar yogurt are better options, but you already knew that, right?

Professional organizations differ in the opinions of NNS. The U.S. Dietary Guidelines cite “insufficient evidence to recommend the use of low-calorie sweeteners as a strategy for long-term weight loss and weight maintenance.” The American Heart Association and the American Diabetes Association have released similar statements. However, the position of the Academy of Nutrition and Dietetics is that “consumers can safely enjoy a range of nutritive sweeteners and nonnutritive sweeteners when consumed within an eating plan that is guided by current federal nutrition recommendations, such as the Dietary Guidelines for Americans, as well as individual health goal and personal preference.”

Nutrition experts make a strong point in that the risks of consuming a high-sugar diet are greater than the risks of consuming nonnutritive sweeteners. In the context of a weight loss plan, the use of NNS will likely help people reach the goal.

Until next time, be healthy!


Leanne McCrate, RDN, CNSC, is an award-winning

dietitian based in St. Louis, Mo.


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