You stick to a healthy high-protein diet but the weight just isn’t coming off. What gives?
A new study from researchers at the U.S Department of Agriculture sheds some depressing light on why a healthy diet with plenty of protein doesn’t mean much if you pair that protein with sugar-laden sodas or juices.
The study, published this month in the journal BMC Nutrition, found that participants who enjoyed meals high in protein burned off fewer calories from fat when they had a sugary soda along with it. For the study, researchers put 27 healthy adults — 14 women and 13 men — in a room calorimeter for 24 hours to measure changes in different molecules, like carbon dioxide nitrogen and oxygen, to determine what kind of fuels they used (like protein, fat and sugar) after eating.
Participants were then given breakfast and lunch either low in protein (7 grams) or high in protein (13 grams), along with a 130-calorie cherry drink flavored with sugar, or one with sucralose. They came back a week later and ate a second meal that was opposite level of protein than they had the first time.
The results? Those who ate a meal with the sugar drink burned fewer calories from fat. Researchers think the body will burn off sugar before burning calories in fat, leading to about 40 fewer calories burned per day.
"We found that about a third of the additional calories provided by the sugar-sweetened drinks were not expended, fat metabolism was reduced, and it took less energy to metabolize the meals. This decreased metabolic efficiency may 'prime' the body to store more fat,” said Dr. Shanon Casperson, lead author of the study.
The results, she said, showed that adding a sugar drink didn’t make the participants feel fuller either, meaning that they were more likely to crave more sugary or salty snacks in the four hours after eating protein and drinking the sweet drink.
“The results provide further insight into the potential role of sugar-sweetened drinks — the largest single source of sugar in the American diet — in weight gain and obesity,” said Dr. Casperson.
The study authors added that more research is needed because it’s such a small study, but the takeaways are clear: Avoid that full-calorie soda and stick with water with your healthy chicken and veggies dinner, especially if you’re trying to stay trim.