Sugary drinks interfere with hormones that tell the body “I feel full,” potentially contributing to obesity and undermining weight loss efforts, a new USC study shows.

The findings, which appear Thursday in the Journal of Clinical Endocrinology and Metabolism, strengthen the case against sugar-sweetened beverages, a significant driver of obesity. Sugary drinks are the single largest source of calories from added sugar for American adults.

“Our study found that when young adults consumed drinks containing sucrose, they produced lower levels of appetite-regulating hormones than when they consumed drinks containing glucose — the main type of sugar that circulates in the bloodstream,” said Kathleen Page, an associate professor of medicine specializing in diabetes and childhood obesity at the Keck School of Medicine of USC.

The impact on hormone signaling was even greater among women who were already obese, as well as men, regardless of whether they were obese or not.

Sugar-sweetened foods, beverages can lead to lower amounts of appetite-regulating hormones

The study included 69 young adults ages 18 to 35 who participated in two study visits where they consumed drinks containing either sucrose or glucose. Sucrose, a combination of glucose and fructose, comes from sugar cane or sugar beets. Glucose is found in honey, grapes, figs and plums.

Participants gave blood samples at 10, 35 and 120 minutes after drinking the drinks. Researchers found that when the participants consumed drinks containing sucrose, they produced lower amounts of hormones that suppress hunger compared to when they consumed drinks containing an equal dose of glucose.

They also found that individual characteristics, including body weight and sex, affected the hormone responses to the different sugars. For example, people with obesity and those with lower insulin sensitivity had a smaller rise in hunger-suppressing hormones after consuming drinks sweetened with sucrose compared to glucose.

Page, who leads the Diabetes & Obesity Research Institute at USC, said the takeaway for the general public isn’t to switch from one sweet drink to another but to try to reduce added sugar altogether.

“The majority of sucrose that people consume in the American diet comes from sugar-sweetened foods and beverages, whereas glucose is found naturally in most carbohydrate-containing foods, including fruits and whole-grain breads,” she said. “I would advise reducing the consumption of sugar-sweetened foods and beverages and instead trying to eat more whole foods, like fruits.”