Sugary drinks and high-protein meals don't mix, study finds

24 Jul 2017 --- The problems that may come with consuming a sugar-sweetened drink along with a high-protein meal have been laid out by a study published in the open access journal BMC Nutrition. The study suggests that combining the two may have a negative effect on energy balance, change food preferences and cause the body to store more fat.

A sugar-sweetened drink was found by the researchers to decrease fat oxidation, which stimulates the breakdown of fat molecules, after a meal by 8 percent. If a sugar-sweetened drink was consumed with a 15 percent protein meal, fat oxidation decreased by 7.2g on average. If a sugar-sweetened drink was consumed with a 30 percent protein meal, fat oxidation decreased by 12.6g on average.

While having a sugar-sweetened drink increased the amount of energy used to metabolize the meal, the increase in the amount of energy used did not mean that consuming additional calories from the drink was evened out.

“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,” says Dr. Shanon Casperson, lead author of the study from USDA-Agricultural Research Service Grand Forks Human Nutrition Research Center in the US. “This decreased metabolic efficiency may ‘prime’ the body to store more fat.”

“We were surprised by the impact that the sugar-sweetened drinks had on metabolism when they were paired with higher-protein meals,” Dr. Casperson continues. “This combination also increased study subjects' desire to eat savory and salty foods for four hours after eating.”

The researchers studied 27 adults of healthy weight – 13 males and 14 females – who were 23 years old on average. Those who took part in the study made two 24-hour study visits. They received two 15 percent protein meals for breakfast and lunch after an overnight fast on one visit, and they consumed two 30 percent protein meals after an overnight fast on the other visit. The increase in protein was counterbalanced by a decrease in carbohydrates.

All meals the participants ate were made up of the same foods, and they provided 17g of fat and 500 kcals. Participants had a sugar-sweetened drink with one of the meals and a non-sugar sweetened drink with the other meal.

By having study participants stay in a room calorimeter, the researchers were able to determine how many grams of carbohydrate, protein and fat study participants were using and how many calories they were burning every minute. A room calorimeter is a 25-square-meter furnished chamber that measures movement, oxygen, carbon dioxide, temperature and pressure, to determine how dietary changes affect energy expenditure and the way nutrients are processed by the body. Study participants stayed inside the room calorimeter for the duration of each study visit.

“Our findings suggest that having a sugar-sweetened drink with a meal impacts both sides of the energy balance equation,” Dr. Casperson explains. “On the intake side, the additional energy from the drink did not make people feel more sated. On the expenditure side, the additional calories were not expended, and fat oxidation was reduced. 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.”

However, dietary changes were measured only for a short time and extrapolating the study data to dietary changes over longer periods of time must be done with caution, according to the authors. As this study was in healthy-weight adults only, the authors also make it clear that overweight individuals may respond differently to dietary changes.

In what could be seen as positive trend, the reduction of sugar in diets is now becoming the norm, according to an article on our sister website FoodIngredientsFirst. This means that swapping out sugar for sweeteners and natural alternatives has become a trend for manufacturers worldwide.

Sugar’s decline in popularity also means that manufacturers are looking at what key trends for the future to keep the soft drinks industry healthy. FoodIngredientsFirst’s recent report, Future Soft Drinks: An Eye on Trends, looks into what is popular at the moment in the soft drinks market and what opportunities can be explored by the industry in the future.