A New Understanding of Processed Food

Research is finally providing reasons for why ultra-processed foods harm people’s health

Robert Roy BrittFollowJun 5

Ultra-processed food — which contains preservatives, emulsifiers, colorings, and other added ingredients — make up more than half of all calories consumed in the United States, according to a 2016 study. That’s a problem, say medical experts, since a large body of research links processed food to unwanted weight gain and poorer health. For example, a study in the journal Circulation found a 42% higher risk of heart disease among people who ate processed meats, and another study found a 10% increase in the proportion of ultra-processed foods in the diet was associated with a significant increase of greater than 10% in risks of breast cancer and cancer overall. Research published earlier this year in JAMA Internal Medicine found that higher consumption of ultra-processed food was linked to “a higher risk of early death from all causes, especially cancers and cardiovascular disease.”

But these studies didn’t show cause, just that there was an association. Like most research on the impact of processed food on human health, these studies were observational. This means researchers ask people what they typically eat (which is often hard for people to remember or share honestly), and they can’t control for other possible causes. For example, someone who eats several bags of Doritos might have worse heart health, but researchers can’t say for certain that it’s due to the chips. Perhaps the individual has a genetic risk, or they are sedentary.

But now, a new study has been able to show processed foods cause poor health. Research published May 16th in the journal Cell Metabolism, found that when people eat highly processed food like sugary cereals for breakfast or fast-food quesadillas for lunch, they consume more calories throughout the rest of the day, and gain more unintentional weight compared to people who breakfast on fruits, nuts, and other minimally processed food. The new research involved 20 people, all who were considered healthy. And while that’s a very small number of study subjects, these people were admitted into a research clinic for a month, so their diet and other variables could be strictly controlled, yielding results not found in observational studies about diet. Here’s how it worked: One group of randomly assigned people were given a healthy diet, such as a parfait made with plain Greek yogurt, strawberries, bananas, walnuts, salt and olive oil, with apple slices and fresh-squeezed lemons. The other group ate things like Honey Nut Cheerios, whole milk with added fiber (to help make up for its absence otherwise), a packaged blueberry muffin, and margarine. The diets were set up to provide equal amounts of sugars, fat, carbohydrates, protein, and sodium. During each phase, the men and women were offered three daily meals and were instructed to consume as much or as little as desired. After two weeks, the groups switched.

While on the processed diet, people consumed an average of 508 more calories per day, added more body fat, and gained two pounds, on average. While on the healthier diet, people lost body fat and dropped an average of two pounds.

“This is the first study to demonstrate causality — that ultra-processed foods cause people to eat too many calories and gain weight.”

An extra 508 calories go a long way. The average sedentary adult woman is advised to eat about 2,000 calories a day (2,400 for men). Moderately active adults should consume around 2,200 (women) and 2,800 (men).

“I was surprised,” says the study’s lead author, Kevin Hall, a researcher at the Laboratory of Biological Modeling within the National Institutes of Health. “Though we examined a small group, results from this tightly controlled experiment showed a clear and consistent difference between the two diets,” Hall says. “This is the first study to demonstrate causality — that ultra-processed foods cause people to eat too many calories and gain weight.”

The men and women in the study said that both diets tasted good and were satisfying, ruling out the possibility that people on the processed food diet simply weren’t satiated and needed to eat more. So, what’s going on? Hall and his colleagues have three ideas:

• People on the ultra-processed diet ate faster, for unknown reasons. Perhaps their guts didn’t have time to signal their brains when they were full.
• Maybe drinks added to the highly processed diets, to increase fiber (like the whole milk), don’t satisfy people’s hunger as much as solid foods do.
• The healthy diets had slightly more protein — 15.6% of calories versus 14% for the bad diets. Maybe peoples’ bodies yearned to make up the difference.

More research like Hall’s needs to be done to gain a better understanding of the relationship between processed foods and overall health. Until then, researchers continue to speculate where the problems stem from. One theory is that highly processed foods often contain empty calories or lower levels of the kinds of nutrients that are beneficial. White flour, for example, has been stripped of the natural fiber and nutrients found in whole wheat. Fiber is important for regulating gut health, and foods high in fiber (like vegetables and whole grain products) have been linked to better heart health and a lower risk of early death. Most Americans don’t get enough fiber in their diets, according to the Food & Drug Administration (FDA).

Packaged food items are also often exceptionally high in sodium. Americans get more than 70% of their sodium from processed foods, not from a salt shaker, according to the Centers for Disease Control and Prevention (CDC), and excess salt has been linked to high blood pressure.

Food labels often also reveal high levels of added sugar, frequently couched in various names like sucrose, fructose, maltose, corn syrup, and so on. Americans are particularly prone to drinking their empty and dangerous calories. More than 60% of youth drink a sugar-sweetened beverage every day, as do half of adults, the CDC says. Excess sugar overloads the liver, upping the risk of liver disease, diabetes, and heart disease, according toHarvard Men’s Health Watch. The American Heart Association recommendsno more than six teaspoons a day for women and nine for men, a can of Coke contains 9.75 teaspoons of sugar. “Reducing added sugar is important because of the evidence linking sugar-sweetened beverages, including sports drinks and fruit drinks, to excess weight, which increases the risk of many types of cancer,” says Colleen Doyle, managing director of nutrition and physical activity at the American Cancer Society. “These beverages make up the largest single source of added sugar in the diet for adults and youth.”

Ultimately, researchers argue that getting people to avoid processed foods is a complex task, given that oftentimes processed foods are convenient, fast, and cheap. “Just telling people to eat healthier may not be effective for some people without improved access to healthy foods,” Hall said in a statement about the his research. But building evidence in favor of eating healthier, less processed foods is a start.