One Twin Eats Ultra-Processed Food Diet While the Other Eats Unprocessed Foods. Two Weeks Later, Here’s What Happened

“Eat less processed food,” we hear this advice all the time. In the summer of 2023, some scientists from King's College London conducted a real-time experiment for BBC Panorama to investigate the health effects of an ultra-processed diet as well as an unprocessed diet. They recruited two 24-year-old twins for the experiment. While one twin, Aimee Kingston, was to spend two weeks on an ultra-processed diet, her sister, Nancy Kingston had to go on an unprocessed diet for the same period. After two weeks, when scientists monitored their health readings, they weren’t surprised. They had found yet another evidence of the possible negative impacts of fatty, processed foods.

Ultra-processed foods, dubbed UPFs, are foods made through industrial processing as the name suggests. Think of frozen pizzas, packaged desserts, colas, sodas, sweetened yogurts, chocolate milk, cookies, and confectionery. Although made from natural substances, these foods often go through harsh processes like hydrogenation, frying, or molding, which strip away or destroy the nutrients embedded in them. UPFs can be identified by packaging labels that show ingredients that are not commonly found in the kitchens, such as high-fructose corn syrup, hydrogenated or interesterified oils, and hydrolyzed proteins.

The diet of both identical twins in the experiment contained the same amount of calories, nutrients, fat, sugar, and fiber, according to BBC Panorama. But, while Nancy felt fulfilled most of the time, Aimee felt constant hunger due to rapid glucose spikes and dips. However, when results came out after two weeks, their health readings showed a stark difference. While Aimee, who ate UPFs, gained a kilo of weight, Nancy lost weight. Aimee’s blood sugar and cholesterol levels went up, while those of Nancy remained balanced.

"In the last decade, the evidence has been slowly growing that ultra-processed food is harmful to us in ways we hadn't thought,” Professor Tim Spector, a professor of epidemiology at King's College London, who studies trends in disease and oversaw the test, told the media channel. He brought attention to the fact that the culprit behind the unpleasant effects of UPF diet, is additives.

Additives are the chemicals that are added to processed foods to enhance their texture, flavor, or shelf life. These are the ingredients that enhance the flavors of frozen foods, lend artificial colors to candies & condiments, gummy chemicals that thicken ice creams and peanut butter, prolong the white bloom in chocolates, and sweeten the sodas or prevent the bread from crumbling too soon. But one of the most dangerous forms of additive is “emulsifiers.” Spector demonstrated how an emulsifier acts like a glue that prevents oil’s separation from water, thereby, triggering a series of health issues.

The results of this BBC experiment are not coincidental. A study published in the journal Cell Metabolism also showed that people who had an ultra-processed diet for 14 days showed significant weight gain as compared to those who had unprocessed foods. Another research published in BMJ suggested that greater exposure to ultra-processed foods was directly associated with higher risks of premature death as well as a host of unhealthy conditions including cardiometabolic disorders and mental disorders.

So, while the objective is to cut off the UPFs from the diet, Kelly Gaines, a dietitian, told Houston Methodist, that one needs to set realistic goals. "Avoiding ultra-processed foods altogether might be ideal from a health standpoint, but it isn't realistic," explained Gaines. "Instead, start by moving more of your diet toward foods that are only somewhat processed or, better still, minimally processed."