February 2025

RESEARCHERS DIG INTO RISKS OF ULTRA-PROCESSED FOODS

How packaged products are made could hold answers to why some are more unhealthy.

A new study is helping to answer a pressing nutrition question: Which ultra-processed foods (UPFs) are harming our health, and which might not be so bad? Researchers believe the problem is the way packaged foods are made. Products such as many frozen pizzas, cereals and chips pack more calories per gram than less-processed foods. And most UPFs have combinations of salt, fat, sugar, and carbohydrates that aren’t generally found in nature, which can make us crave them. Diets high in packaged foods without those traits, such as canned peaches or refried beans, don’t seem to lead people to overeat and gain weight, at least not as much. Thus far, those are the findings of a continuing study investigating how ultra-processed food affects our bodies, and how there might be a way to create the “healthy” ultra-processed food that’s still convenient; for example, a frozen meal with brown rice, beans, and lots of vegetables. 

UPFs make up about 58% of the calories that U.S. adults and children ages 1 and older consume in a day. Foods are generally considered ultra-processed if they contain ingredients you wouldn’t find in a home kitchen, such as high-fructose corn syrup and emulsifiers. Yet many scientists believe not all these foods are equally bad, and that some might be reasonably healthy. Recent studies have linked diets high in UPFs to increased risks of obesity, type 2 diabetes, cancer, cardiovascular disease, and depression.  When companies make, say, an energy bar, they often break down the cellular structure of the raw ingredients and remove the water. Getting rid of water makes sense for food safety, since moisture promotes the growth of bacteria.  The process also makes foods more energy-dense, meaning they contain more calories per gram than do many minimally processed foods. In the study the meals with energy-dense foods had about 2 calories per gram, compared with about one calorie per gram for the meals with fewer energy-dense foods. In addition, many packaged foods combine fat, sugar, sodium, and carbohydrate in ways not typically found in nature. For instance, bagels are usually high in carbohydrates and sodium, muffins are high in fat and sugar, and French fries are high in fat and sodium. Researchers call these types of foods “hyperpalatable” and they have a strong effect on the brain’s reward system. This makes it difficult to stop eating them. Many seemingly healthy foods are hyperpalatable, including many non-fat yogurts (high in sugar and added fructose) and salted nuts (high sodium, high fat), but whole-milk dairy and plain unsalted nuts are not. 

In the study, participants were given three different types of diets: energy dense, fewer energy dense foods, and unprocessed foods. The diets contained roughly the same amounts of calories, fat, sugar, sodium, and fiber. Participants reported feeling just as full and satisfied on all diets. But when they were on the energy-dense diets they ate about 1,000 more calories a day then they did while eating the unprocessed foods diet. People gained about one pound after a week on the energy-dense diet. They lost about half a pound when on the minimally processed and unprocessed foods diets. The findings suggest that eating packaged foods doesn’t automatically result in overeating or weight gain, as long as you stick to foods such as canned refried beans or fruit cocktail, which are low in calories per gram and don’t have the problematic combinations of fat, salt, sugar, and other carbohydrates such as high-fructose corn syrup. 

There are other concerns about convenience foods beyond weight gain. Some of the additives that many contain have been linked to health problems. The NIH study is far from complete. But so far, the findings suggest you can choose healthier packaged foods by checking labels and calculating calories per gram. Avoid foods that clock in at two calories per gram or more, such as frozen meatballs, and stick to those that are around one calorie per gram, like whole-milk plain yogurt. Or you can combine foods to dilute the overall energy density of your meal. Instead of eating chicken fingers with mac and cheese, have them with a big salad. To avoid hyperpalatable foods, look for products that are low in sodium. This can include items such as low-sodium frozen meals and soups.

Andrea Petersen