Bethesda, MD--The National Institute of Health (NIH) in collaboration with the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) announced results of a randomized controlledtrialthat examined the effect of heavily versus minimally processed diets.

Subjects (10 healthy females and 10 healthy males) were admitted to the NIH Clinical Center for one month and provided meals consisting of ultra-processed foods (those with ingredients predominantly found in industrial food manufacturing, such as hydrogenated oils, high-fructose corn syrup, flavoring agents, and emulsifiers) or meals with minimally processed foods equaling the same amounts of macronutrients. Each diet was followed for two weeks.

The result: Study subjects ate about 500 calories more per day on the ultra-processed diet than they did on the unprocessed diet. On average, they gained 2 pounds while on the ultra-processed diet and lost an equivalent amount on the unprocessed diet.

"We need to figure out what specific aspect of the ultra-processed foods affected people's eating behavior and led them to gain weight," said Kevin D. Hall, Ph.D.,NIDDKsenior investigator and the study's lead author in a report onScience Daily. "The next step is to design similar studies with a reformulated ultra-processed diet to see if the changes can make the diet effect on calorie intake and body weight disappear."