If you eat a lot of highly processed foods, chances are you eat more than with an unprocessed diet.
Researchers have long suspected a link between highly processed foods and the obesity epidemic.
Today, in a report published in the journal Cell Metabolism, experts undertook the first randomized controlled trial comparing the differences in calorie consumption between unprocessed and ultra-processed diets.
Even when the two diets in the trial were matched for items such as fat content, participants in the ultra-treated diet ate even more food and gained more weight.
“Because meals were designed to be matched for carbohydrates, fat, sugar, salt and calories.
However, Mr. Hall said the researchers observed that the ultra-treated diet increased caloric intake by about 500 calories per day.
“It was a surprise,” said Hall.
According to him, the consumption of highly processed foods has been associated with obesity and poor health in observational studies, but there has never been a randomized controlled trial to determine whether processed foods actually cause overeating or weight gain.
“Most nutritional studies focus on the nutrient content of foods, so I was skeptical about whether food processing is important other than their nutrient content,” Hall said. “We, therefore, thought it was important to conduct the first[randomized controlled trial] where subjects were exposed to ultra-processed diets versus unprocessed diets matched for a variety of nutrients to see if ultra-processed foods caused overeating and weight gain.
Eat more ultra-processed foods
As part of this research, Hall and his team called on 20 healthy volunteers.
They were admitted to the NIH Metabolic Clinical Research Unit for one month.
Members received either an ultra-treated or untreated plan for two weeks and then switched plans.
They ate three meals a day and were given bottled water and ultra-treated or unprocessed snacks. Participants could eat as much as they wanted and the amounts of everything they ate were measured.
The researchers used NOVA’s food classification system, which classifies foods according to the amount processed, to select participants’ foods.
As part of the ultra-treated diet, participants received Cheerios with honey and nuts, whole milk with added fiber and a blueberry muffin with margarine for breakfast.
Participants who ate an unprocessed diet received a perfect one with strawberries, bananas, nuts, salt, olive oil, Greek yogurt and apple slices with lemon zest.
After two weeks of an ultra-treated diet, participants took an average of two pounds. Those on an untreated diet had an average weight loss of two pounds.
Dana Hunnes, Ph.D., senior dietician at the University of California Medical Center in Los Angeles, said the research results are not surprising.
“Ultra-processed diets tend to contain foods that are higher in calories and lower in the water, making each food less satisfying and less satisfying,” she told Healthline. “To achieve the same feeling of satiety in the stomach – or feeling of satiety – that may have more to do with volume than with caloric intake, it would make sense for more dense caloric foods to be consumed (and therefore more calories) than in an unprocessed diet.
Why do you eat more?
The researchers made some hypotheses about why participants in an ultra-treated diet ate more food.
One of the reasons is the speed at which they ate.
“People ate the highly processed foods more quickly, which may have contributed to overeating,” said Mr. Hall.
Kristin Kirkpatrick, MS, Registered Dietitian and Director of Wellness Nutrition Services at the Cleveland Clinic Wellness Institute in Ohio, says people need to be aware of how quickly they eat their food.
“Many studies cite prolonged chewing and mindfulness as effective weight loss tactics,” she told Healthline. “Eating fast obviously means eating more – more food, more calories and too much fuel at the end of the day that can’t be burned, resulting in abundant energy still there before going to bed.
The researchers acknowledge that one of the notable limitations of the study was that all the food given to participants was prepared by someone else. This does not take into account the convenience or cost of the food consumed, which are common reasons why a person can choose something ultra-treated.
“Processed foods are fast and, in these busy times, people often opt for speed and convenience,” said Lauri Wright, Ph.D., Assistant Professor of Public Health at the University of South Florida, Healthline.
“Highly processed foods often contain large amounts of sugar, sodium, and fat. Examples of foods to avoid include chips, hot dogs, instant soups, soft drinks, and packaged baked goods,” she says.
What can you do about it?
Not all processed foods are bad.
Wright says some unprocessed foods can be useful for busy people.
“Every time we cook, cook or prepare food, we process food,” she says. “Low-processing foods can actually help you eat more nutrient-rich foods. Milk and fruit juices are sometimes fortified with calcium and vitamin D, and breakfast cereals may have added fibre. Canned fruit is a good option when fresh fruit is not available. Some unprocessed foods, such as cut vegetables and pre-washed spinach, are convenient quality foods for busy people.”
If you want to minimize your consumption of processed foods, try to do more food preparation and cooking at home. “Base your food on whole foods, such as vegetables, peas and whole grains,” Wright called for. “Eating processed foods in moderation is good, but avoid foods that contain a lot of sugar, fat and sodium.”