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Diet Soda Doesn’t Cause Weight Gain — Unless Combined With Certain Foods

Hint: You don't want fries with that.


It’s long been debated whether drinking low calorie and diet sodas can actually cause you to gain weight instead of lose it. According to a new study, it’s not the beverage on its own that can make your scales tip, but the type of food you’re eating along with it.

Research from Yale University found that on its own, drinks sweetened with sucralose — one of the most common sugar substitutes for diet drinks — won’t affect your metabolism or brain in any adverse ways. However, if you happen to chow down on some carbs while you sip the soda, that’s when things start to get mixed up. More specifically, it can “rapidly impair glucose metabolism and result in longer-term decreases in [response from the] brain, but not perceptual sensitivity to sweet taste, suggesting dysregulation of gut-brain control [over] glucose metabolism.”

Senior study author Dana Small broke all of that scientific jargon down in a press release: “When the drink was consumed with just the low-calorie sweetener, no changes were observed; however, when this same amount of low-calorie sweetener was consumed with a carbohydrate added to the drink, sugar metabolism and brain response to sugar became impaired.” 

Small and her colleagues came to this conclusion by observing 45 adults between the ages of 20 and 45 who don’t ordinarily consume many things with low-calorie sweeteners. The participants were given seven low-calorie drinks over the course of two weeks. They used brain scans to confirm that the combination of diet drinks and carbohydrates caused the brain to misinterpret sweetness. The effect lingered for at least two hours, meaning any carb consumed within that time — not just while they were drinking the low-calorie beverage — resulted in the same mixed messages to the brain.

This was obviously a small study and more research needs to be done, but it shines an important and fascinating new light on what we previously thought about diet drinks. “The bottom line is that, at least in small quantities, individuals can safely drink a diet soda, but they shouldn’t add French fries,” Small explained.

Maybe we should all be drinking more water on a regular basis, anyway, eh?

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