People who eat a lot of ultra-processed foods, such as frozen entrees, commercial white bread and packaged side dishes, tend to consume more calories – as much as 500 a day – than those who eat foods that aren’t processed, a new study suggests.
That’s according to a new study conducted by researchers at the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland.
The increase in calorie intake with ultra-processed foods occurred despite the fact that the meals were matched for salt, sugar and fat, nutrients people think cause weight gain.
The results underscore the futility of cutting out specific nutrients to lose weight. The findings suggest it’s far more beneficial to reducing ultra-processed foods and not focusing on specific nutrients like fat and sugar.
About the study, foods eaten
The researchers rounded up 20 volunteers who were willing to live in the lab for 28 days and consume only the foods that were offered to them.
Each participant was randomly assigned to get meals either containing ultra-processed foods for two weeks or meals with only unprocessed foods. At the end of two weeks, the participants switched to the other group’s diet.
Included in the ultra-processed food category were items such as canned ravioli, canned peaches in heavy syrup, turkey sausages, frozen macaroni and cheese, frozen fried chicken. In the unprocessed category were fresh fruits, homemade hash brown potatoes, scrambled fresh eggs, grilled chicken breast, frozen but unprocessed vegetables.
Meals were designed such that they contained the same amount of nutrients and calories, whether they were ultra-processed or unprocessed.
The researchers calculated how many calories each volunteer should be eating each day to maintain their weight and then doubled that amount for the meals that were offered. Volunteers were told to eat as much as they wanted, and the researchers measured the calories left unconsumed.
Ultra-processed diet increases hunger hormone, grehlin
The volunteers reported that both diets tasted good and were satisfying, which meant they weren’t eating less of the unprocessed foods because of taste issues.
One big difference was that levels of an appetite-suppressing hormone increased when participants consumed unprocessed foods and similarly, ghrelin, a hormone that causes hunger, was lower in those eating an unprocessed diet. Lower levels of ghrelin may have suppressed hunger and allowing the unprocessed food eaters to consume fewer calories.
An extra 508 calories per day resulted in weight gain
During the two weeks the volunteers ate ultra-processed food, they consumed an average of 508 more calories per day compared to the amount they ate on unprocessed food days. Moreover, during the two weeks of consuming ultra-processed foods volunteers gained an average of two pounds as compared to a loss of two pounds after two weeks of eating unprocessed food.
While they don’t yet know why people ate more and gained weight on a diet rich in ultra-processed foods, the researchers have some theories.
It’s possible that the processed foods combine high levels of sweetness and fat in a way that would not occur in nature, which may stimulate the reward region in the brain.
Another hypothesis suggests that people ate more ultra-processed food because these items may be softer and easier to chew and swallow. The researchers did notice they ate these foods more quickly. When you eat that quickly, it doesn’t give your gut and brain enough time to process the signal that you’ve had enough to eat.
Source: Cell Metabolism, online May 16, 2019.
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