Findings Surprised Researchers
DiFeliceantonio says she was initially “surprised” that ultra-processed foods didn’t have a big impact on blood sugar, but did impact insulin. “I called up the lab and said, ‘Is there something wrong with this data?’” she says. “The people in the lab didn’t know the conditions [of the study]. They just had the blood samples.”
She says the increase in insulin may be due to the concept that ultra-processed foods are, in a way, “predigested.” “They go through things like high heat and enzymatic degradation, which potentially makes the nutrients more bioavailable,” she says.
Sandra Zhang, RDN, LDN, a registered dietitian-nutritionist at the Frances Stern Nutrition Center at Tufts Medical Center in Boston, agrees that this likely plays a role. “Ultra-processed foods are often easier to digest, so nutrients may become available more quickly,” she says. “That can lead to a faster insulin response, although we still don’t know the exact mechanism.”
The concern with a high insulin response is that it can raise the risk of insulin resistance, which is when the body doesn’t respond as well to insulin, DiFeliceantonio says. Insulin resistance and frequent high blood sugar are precursor symptoms to type 2 diabetes, she says.
DiFeliceantonio notes that these effects only lasted for a short time in participants. However, she says that the findings raise a concern that this process could raise the risk of developing chronic metabolic diseases like type 2 diabetes and obesity in people who eat a lot of ultra-processed foods.
But Zhang says the real-world impact of eating ultra-processed foods may be slightly different, given that people tend to eat a greater volume of food, and thus more calories, from these products in one sitting.
“Ultra-processed foods are engineered to be more appealing and promote frequent over-consumption, which can lead to higher blood sugar levels from increased intake of refined carbs and added sugar,” she says.
There Are Some Limitations to Consider
While robust and tightly controlled, the study was relatively small. The test meals also included different protein sources, which may have influenced the insulin response. The ultra-processed meal contained more additives, and the body’s response to the meals may vary based on how many calories people consume in real-life settings.
The researchers also noted that people tend to eat ultra-processed foods “more rapidly” and as much as they want, which could influence the impact on the body.
Findings Suggest People Should Question What’s in Their Food, According to Experts
Ultra-processed foods may impact the body in more ways than one, Zhang says. “Food processing itself may affect how the body responds to food, beyond just calories and nutrients,” she says.
DiFeliceantonio acknowledges that most people are aware that ultra-processed foods aren’t the healthiest choice. “People have heard a lot about ultra-processed foods being bad for them. I don’t think it’s useful to hear that again,” she says. “But it’s worth thinking about the food environment we’re in and systemic changes that can be made to help everybody eat healthier.”
Overall, Zhang suggests prioritizing minimally processed foods in the diet. “Enjoy ultra-processed foods in moderation,” she says.
