‘Ultra-processed’ is a term used to describe foods that have been plugged full of additives and contain very little whole food ingredients.

Now, a recent study says that eating a diet high in ultra-processed foods can lead to weight gain.

The study looked at a group of adults in their thirties.

“One diet was ultra-processed, and the other one wasn’t processed at all; and they looked at these people for two weeks; changing the diet half way through, so all of the individuals were on both of the diets,” said Cleveland Clinic’s W. Scott Butsch, M.D., who did not take part in the study. “In the end, they found that those who ate the ultra-processed foods gained weight.”

Dr. Butsch said people gained weight on the ultra-processed diet – an extra 500 calories each day they were on the diet. However, he said it is not clear why this happened – whether the food caused changes in the brain making them eat more calories, or if the food was higher in energy density or other factors.

To know if a food is ultra-processed, Dr. Butsch recommends looking at the list of ingredients – if it’s a long list – it’s probably very processed.

He also said weight gain is caused by more than just food and nutrients (or lack of nutrients), but also the biological reaction that happens when we eat certain foods.

The fiber found in vegetables and whole grains is not easily digested, so when it gets to the colon, the bacteria in the gut is improved. Whereas when we eat ultra-processed foods that are low in fiber, the breakdown of the foods in our digestive tract is different.

Dr. Butsch said a diet full of fruits, vegetables and whole grains is the best way to go for our health and waistlines, but some worry about the cost.

He recommends taking advantage of summer farmer’s markets to get our eating habits off to a fresh start.

“Certainly in the summer months, there are a lot of crops, and a lot of farmers are selling their product, and it’s a great idea to try to see where your local farmer’s markets are,” said Dr. Butsch. “This is food that usually is cheaper than you would get in a grocery store, so, obviously from a cost perspective, it’s a great idea to check these out and try different foods.”

Complete results of the study can be found in Cell Metabolism.