There is growing evidence that consumption of a diet with a large component of ultra-processed foods carries a heightened health risk.
For years, scientists have been linking ultra-processed foods to a variety of poor health outcomes, including cancer, obesity and even an increasing risk of death. Most of these studies, however, have been limited to questionnaires and diet records that rely on people to accurately report what they’ve eaten, and can’t establish direct cause and effect.
A National Institutes of Health small-scale study gives credence to the potential for increased weight gain in participants consuming ultra-processed foods.
The clinical study by Kevin Hall at the National Institute of Diabetes and Digestive and Kidney Disease was intended to monitor caloric intake and weight gain. It offered its participants one of two nearly identical menus.
Both contained the same number of calories, and comparable amounts of carbohydrates, fats and proteins. Even the diets’ fiber, sugar and sodium contents were matched. Nutrient-wise, they were about as similar as two meal plans could get.
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Unique approach of study
Hall and his team decided to do what no other group had done before: Round up 20 people, house them at the National Institutes of Health Clinical Center, and prepare, serve and track every single morsel of food they ate for a month.
Each person was randomly assigned to either an ultra-processed or unprocessed menu for the first two weeks, and then switched. Both diets consisted of three meals and a glut of snacks, providing almost 4,000 calories each day, and participants were told to eat as much or as little as they wanted.
In terms of their nutritional composition, the two diets were equivalent on almost every front, down to the average number of calories per gram of food. But while ultra-processed foods had no part in the unprocessed menu, they contributed more than 80 percent of the calories in the ultra-processed diet.
It took some serious finagling to get the menus to match, while keeping the ratio of carbohydrate to fat to protein within a healthy range, Hall says. The team also had to take great pains to keep the study’s results mum as they unfolded, even outfitting participants in loose-fitting clothing to mask any weight gain or loss.
But the work paid off. In the end, the only real difference between the groups was the proportion of ultra-processed foods in their diets.
Hall and the research team were surprised to discover how quickly changes in eating behavior unfolded. When put on the ultra-processed diet, participants started eating an average of 500 extra calories a day, resulting in several people gaining weight and body fat over the two-week stint.
The difference had nothing to do with the amount of food they’d been offered, or even how good it tasted (when asked, participants reported the two menus were equally appetizing and satisfying). But the inclusion of ultra-processed food had triggered a subtle, and likely subconscious, shift in behavior.
Some final comments
The study was short-term but the intervention was well-controlled. There’s no telling whether these results will hold true on a longer time scale. However, a couple of comments follow to provide some insight.
Ashley Gearhardt, a psychologist studying food addiction at the University of Michigan who was not involved in the study, said “I can’t think of another study that has been this well controlled for so long … that allows us to make much more confident interpretations of what these foods are really doing.”
There’s no quick fix to this problem, but the path forward is with studies like these, according to Dana Small, a psychologist and neuroscientist studying food choice at Yale University not involved with the study.
By pinpointing the mystery factor in ultra-processed foods — whatever it is that’s causing us to eat more and gain weight — researchers may be able to partner with the food industry to cook up cheap, convenient foods that can still confer some health benefits.
Though it’s not yet clear why ultra-processed foods have this effect, the results underscore the importance of an issue that goes beyond effective dieting. With their cheapness, convenience and long shelf life, ultra-processed foods now make up more than half the calories Americans eat. These numbers tick even further upwards for underrepresented minorities, as well as in lower income populations.
Additional reference information
A 2021 multi-national cohort study concluded that the consumption of ultra-processed foods was associated with weight gain and obesity in adults. Details available at iarc.who.int.
A summary by Harvard Health on what makes up processed versus ultra-processed foods is available at health.harvard.edu.
Mark Mahoney served as a Peace Corps Volunteer for over four (years in Latin America, has been a Registered Dietitian/Nutritionist (R.D.N.) for over 35 years and completed graduate studies in Public Health at Columbia University. He can be reached at firstname.lastname@example.org.
This article originally appeared on Tallahassee Democrat: Want more motivation to skip ultra-processed food? Check out new study