Scientists Gave People 2 Nearly Identical Meals. One Triggered Much More Insulin. : ScienceAlert

You’ve probably heard a bit about ultra-processed foods by now, and if so, you likely know they’re not the healthiest things you can eat.

These industrially manufactured foods are increasingly being linked to heightened risk of diseaseand research suggests they may affect how we think and harm our mental health.

In light of all the concerning associations scientists are findingit’s easy to assume that ultra-processed foods are unhealthy because they’re packed full of nutritionally poor ingredients – but what if there’s more to it than that?

“We know that the majority of ultra-processed foods are high in fat, they’re high in sugar, they’re low in fiber, and they’re low in protein,” says neuroscientist Alex DiFeliceantonio from Virginia Tech.

“But if we artificially hold all of those things constant, is there something about the processing that leads to a different outcome?”

The answer, it seems, is yes, according to a surprising finding reported in Nature Metabolism.

In their study, DiFeliceantonio and her team recruited 57 healthy-weight adults, with an average age of 26 years. Of these, 32 people took part in an eating experiment, in which they ate two separate meals on two separate days, in a randomized order.

One of the meals was made up of ultra-processed foods, including deli turkey, instant mashed potatoes, a chocolate chip cookie, frosted wheat cereal, veggie chips, a small sandwich made of white bread with peanut butter and jelly, and a small serving of water.

The other meal was made up of minimally processed foods, including a hard-boiled egg, banana, cranberries, cheese, and some sea salt.

The kicker was that these two meals – while very different-looking on the plate – were largely the same from a nutritional perspective, being matched for both nutritional composition and energy (300 calories each).

“The two meals are matched within 1 percent of carbs, fat, proteins, calories, water, and salt,” says Virginia Tech biomedical researcher Zach Hutelin, the study’s first author.

“If these meals had a nutritional label, they would be practically identical.”

While their nutritional labels might have been the same, the metabolic responses they triggered turned out to be very different.

A series of blood samples taken during the three hours after each meal showed that blood glucose responses were generally similar for both meals, although glucose remained elevated for longer after the ultra-processed meal.

The contrast in insulin response was more marked, with insulin levels rising significantly higher after the ultra-processed meal and staying higher for about two hours, before both meals returned to near-baseline levels by the three-hour mark.

The ultra-processed meal triggered a higher metabolic rate and greater fat burning during the three-hour observation window, but less carbohydrate burning than the minimally processed foods.

“We were shocked when every single metabolic metric differed,” Hutelin says.

“What we noticed with the ultra-processed food is that insulin response was much higher and blood sugar stays a little bit higher for a little bit longer.”

While we don’t know for sure why the metabolic responses were so different, the research offers a few clues.

In a separate experiment, the participants viewed pictures of ultra-processed and non-ultra-processed foods while having their brain activity monitored by functional MRI.

For the participants who also took part in the meal-eating phase of the experiment, the brain activity showed an association between neural activity in the striatum (a part of the brain involved with reward systems) and how they burned carbohydrates in the meal-eating session.

The researchers suggest that this could mean that the way our bodies burn food for fuel is linked to specific cues about the foods we’re eating – and, possibly, their level of processing.

“Collectively, our findings support the hypothesis that food processing might influence metabolic responses and reward processing through mechanisms extending beyond caloric content and macronutrient composition,” the researchers explain in a briefing on their study.

“These mechanisms might involve altered nutritional availability as a result of altered physical structure in ultra-processed foods.”

Another possibility is that commercial food additives incorporated in ultra-processed foods might affect our metabolic response when we eat them, which is something the researchers intend to examine next.

The findings are reported in Nature Metabolism.