People who drink sugary beverages, such as soda or fruit juice, daily tend to gain a type of body fat associated with diabetes and heart disease, a new study finds.
Researchers looked at about 1,000 middle-age people over a six-year period and found that those who drank sugar-sweetened beverages tended to have more "deep," or visceral, fat. This type of fat wraps around the internal organs, including the liver, pancreas and intestines; affects hormone function; and may play a role in insulin resistance, the researchers said.
Previous research has linked sweet drinks with other health risks. "There is evidence linking sugar-sweetened beverages with cardiovascular disease and type 2 diabetes," Dr. Caroline Fox, lead author of the new study and a former investigator with the Framingham Heart Study of the National Heart, Lung, and Blood Institute, said in a statement. "Our message to consumers is to follow the current dietary guidelines and to be mindful of how much sugar-sweetened beverages they drink."
In the new study, the researchers gave a dietary survey to 1,003 people, nearly half of them women, whose average age was 45. The participants answered a variety of questions, including how often they consumed drinks with added sugar -- largely with sucrose or high fructose corn syrup -- because these beverages are the largest contributors of added sugar intake in the United States, according to the study, published in the journal Circulation.
All of the participants underwent computer tomography (CT) scans at the beginning and end of the study, allowing the researchers to measure changes in visceral fat.
After controlling for several factors that can affect people's amount of visceral fat -- including their age, gender, physical activity level and body mass index (BMI) -- the researchers found that over the course of the study, the participants who never drank sugar-sweetened beverages and the participants who drank them only occasionally gained the least amount of body fat: about 40 cubic inches each (or 658 cubic centimeters and 649 cubic centimeters, respectively), on average.
Those who drank the beverages frequently (at least once a week, but less than daily) gained 43 cubic inches (707 cubic cm) of visceral fat, on average.
Daily sugary-beverage drinkers gained the most visceral fat -- 52 more cubic inches (852 cubic cm), on average -- at the end of the study than they had at the study's start, the researchers found. Overall, people who drank sugary drinks were more likely to be male, younger, smokers, engaged in slightly more physical activity and less likely to have diabetes, the researchers noted.
Interestingly, there was no association between diet soda and visceral-fat increase, likely because diet soda tends to be low in calories and sugar, the researchers said. However, they noted that the diet-soda drinkers in the study were less likely to be engaged in physical activity, had higher BMIs and had a higher prevalence of diabetes than those in the study who didn't drink diet soda.
Exactly how sweet drinks may get converted into visceral fat is unknown, the researchers said. But the results clearly show that "individuals who consumed higher amounts of sugar-sweetened beverages gained more visceral fat over time," Fox stated.
Perhaps the high amounts of sugar in these drinks contributes to insulin resistance, or a reduced ability of body cells to take up sugar from the blood, and this contributes to the development of visceral fat, said study co-leader Dr. Jiantao Ma, a postdoctoral fellow at the National Institutes of Health. Insulin resistance can increase people's risk for type 2 diabetes and heart disease, he said.
Visceral fat is also associated with other maladies. Being pear-shaped because of belly fat is linked to an increased risk of kidney disease. Moreover, women who have increased belly fat are at increased risk of developing osteoporosis, research finds.
The American Heart Association recommends that women consume no more than 100 calories per day from added sugars, including those found in sweetened drinks, and that men consume no more than 150 calories per day from added sugars.
People who are trying to keep off the pounds can dive into aerobic exercises or eat more vegetables and fiber, studies suggest.
"To policymakers, this study adds another piece of evidence to the growing body of research suggesting sugar-sweetened beverages may be harmful to our health," Fox said in the statement.