Diet soda may actually lead to weight gain by causing brain to crave more food

LOS ANGELES, Calif. — Diet soda is often a go-to beverage for many people trying to lose weight. Unfortunately, a new study finds drinks containing the artificial sweetener sucralose may be hurting the dieting efforts for both women and the obese. Researchers at the Keck School of Medicine of USC say diet sodas actually cause the brain to experience more food cravings than normal sugary beverages.

Study authors note this is the largest study to date examining how artificial sweeteners, or nonnutritive sweeteners (NNS), influence brain activity and appetite. Over 40 percent of U.S. adults drink some variety of NNSs as a calorie-free alternative to regular soda. Although some dieters do lose weight while drinking diet soda, researchers say the health pros and cons of artificial sweeteners are still unclear. Scientists continue to debate how much of an impact these substances have on appetite, glucose metabolism, and body weight.

“There is controversy surrounding the use of artificial sweeteners because a lot of people are using them for weight loss,” says Kathleen Page, MD, the study’s corresponding author and an associate professor of medicine at the Keck School of Medicine, in a university release. “While some studies suggest they may be helpful, others show they may be contributing to weight gain, type 2 diabetes and other metabolic disorders. Our study looked at different population groups to tease out some of the reasons behind those conflicting results.”

Diet soda lowers the ‘I feel full’ signal in the brain

Researchers examined 74 participants during three experiments measuring their brain activity while drinking various beverages. The volunteers varied from healthy weight individuals, to overweight, to obese dieters. The group drank 300 milliliters of a drink containing sucrose (regular table sugar), a diet drink sweetened with the NNS sucralose, and water.

Two hours later, study authors used functional magnetic resonance imaging (fMRI) scans to examine each person’s brain activity as they viewed pictures of high-calorie foods like a burger or donut. Specifically, researchers focused on brain regions responsible for appetite and food cravings as the group looked at these tasty images.

The team also measured each person’s blood sugar levels, insulin, other metabolic hormones in the blood, and the amount of food each person ate at a snack buffet following the brain scans. Results reveal that both women and obese participants experienced increased activity in the brain areas controlling food cravings and appetite after drinking diet soda-sucralose beverages. The activity was greater than when these individuals drank the real sugar beverage.

Researchers add they discovered an “across-the-board decrease” in the levels of hormones that tell the body “I feel full” after drinking sucralose-containing drinks in comparison to sucrose-containing drinks. The team says this points to artificial sweeteners being ineffective at suppressing hunger.

Females, people with obesity ‘more sensitive to artificial sweeteners’

Women in the experiment drinking sucralose-containing beverages also ate more at the snack buffet than those having a regular sugary beverage. Study authors did not see the same change among men in the experiment.

“Our study starts to provide context for the mixed results from previous studies when it comes to the neural and behavioral effects of artificial sweeteners,” Page concludes. “By studying different groups we were able to show that females and people with obesity may be more sensitive to artificial sweeteners. For these groups, drinking artificially sweetened drinks may trick the brain into feeling hungry, which may in turn result in more calories being consumed.”

The study appears in the journal JAMA Network Open.

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