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What's Worse: Regular or Diet Soda?

Which is healthier: regular or diet soda? It's a question health-minded consumers have been asking for as long as these products have been on supermarket shelves.

Though many would assume diet trumps regular, recent reports of artificial sweeteners' effects on weight gain and belly fat have left many people scratching their heads.

Although one is filled with health-harming sugar and chemicals, the other relies on artificial sweeteners and even more chemicals to achieve its signature taste. So which is the lesser of the two evils? Five out of six nutrition experts say diet. Although everyone we spoke with was forced to pick a side, it's worth noting that a few of our experts are still teetering back and forth, proving just how difficult of a question this is to answer—even for health professionals.

According to registered dietitian Isabel Smith, which soda you should pick all depends on your sipping habits: "If you only drink the stuff on a rare occasion, I suggest diet—there's no reason to waste the calories," she says. "However if you sip on a daily basis, stick with the regular, sugar-sweetened variety." Although a regular can of soda contains an entire day's worth of sugar, Smith explains that when drank consistently over a long period of time, artificial sweeteners may throw off the ratio of healthy to unhealthy gut bacteria, which may affect the body's ability to maintain a healthy weight. Research backs Smith's advice, and some articles even point to additional mechanisms. A recent study in the journal Diabetes Pro, for example, found that people who drank two or more diet sodas a day experienced waist-size increases that were six times greater than non-drinkers. The deceptively sweet artificial sweeteners in diet beverages trick the metabolism into thinking sugar is on its way, spikes insulin levels, and shifts the body from a fat-burning to a fat-storing state, according to the study researchers.

Registered dietician Lisa Moskovitz agrees that people should pick their go-to soda based on how often they indulge, but she has a different perspective on which types makes sense for whom. "If you're going to indulge once in awhile, either regular or diet soda is fine—especially if it's less than once a week and no more than an 8-ounce can," says Moskovitz. "However, despite common and numerous allegations that diet drinks are pure evil, I still believe diet is the lesser of two evils when compared to regular, empty calorie soda," she adds. "Though some studies have linked artificial sweeteners to long-term weight gain, at this point there is not strong enough evidence to support or ban drinking diet soda."

And then there are those who picked a side based on their own personal experience. "In no way am I saying that any type of soda is healthy, but when it comes to weight loss, my experience clearly points to diet soda as the better choice," says registered dietitian and personal trainer Tammy Lakatos Shames. "Time and time again, clients who have switched from regular soda to diet soda, prior to working with me, have dropped pounds with that being the only dietary change they made." Torey Armul, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics, puts it this way: "You save a substantial amount of calories and consume significantly less simple sugars when you pick diet over regular. Plus, decades of research show that a can or two of diet soda per day is safe. You're better off drinking a diet soda and saving calories for weight control or more nutritious and satiating food choices (like these 50 Best Breakfast Foods for Weight Loss—Ranked)," Armul adds. Plus, as registered dietitian and certified dietitian-nutritionist, Ilyse Schapiro notes, "repeatedly drinking regular soda can lead to weight gain, insulin resistance, diabetes and tooth decay." Added sugars can also spike blood sugar, causing fatigue and cravings for more sugar, according to Leah Kaufman, a New York City-based registered dietitian and certified dietitian-nutritionist. "Replacing diet soda with regular soda will ultimately reduce the risk of diabetes, heart disease, and weight gain," Kaufman says.

Although the majority of our panel says diet is the better pick, not all diet sodas are created equal. To find out which ones are the best for your health, check out our exclusive report, 38 Top Diet Sodas—Ranked!

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Dana Leigh Smith
Dana has written for Women's Health, Prevention, Reader's Digest, and countless other publications. Read more about Dana Leigh
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