Why people get fat from processed foods

If a person's diet consists of ultra-processed foods, they consume 500 more calories daily than when their diet includes minimally processed foods. These are the results of a U.S. National Institutes of Health study published in Cell Metabolism.

This is the first randomized study to examine the effects of ultra-processed foods. Processed foods are packaged or convenience foods that contain added sugars, refined carbohydrates, industrial fats, sodium and synthetic flavorings and preservatives.

The experiment involved 20 healthy adult volunteers (10 men and 10 women, with an average age of 31). For four weeks, they lived in a research center where they ate only ultra-processed foods or, conversely, minimally processed foods for two weeks at a time (in random order). Both sets of meals contained equivalent amounts of calories, sugar, fiber, fat, and carbohydrates. Participants could eat as much as they wanted.

The diet, which consisted of processed foods, contained no obvious unhealthy foods. The foods offered by the researchers were consumed by many daily and were considered nutritious - breakfast cereals, muffins, white bread, sweet yogurt, low-fat potato chips, canned foods, processed meats, fruit juices and diet drinks.

The second diet was based on the consumption of minimally processed foods-fresh fruits and vegetables, eggs, legumes, fried chicken, fish and beef, and whole grains, nuts and seeds.

The most striking finding was that by eating ultra-processed foods, participants gained 500 extra calories a day, mostly from carbohydrates and fats. This resulted in an average weight gain of two pounds (about 1 kg) over two weeks.

The researchers found that eating unprocessed foods increased appetite-suppressing hormone levels, while ghrelin (which stimulates hunger) levels decreased.

The researchers believe that some differences in protein levels between ultra-processed and unprocessed diets could potentially explain up to half of the difference in caloric intake.

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