Ultra-Processed Foods May Raise Insulin Levels Regardless of Nutrition

Ultra-processed foods make up over half of the average American diet, but new research shows that how these foods are manufactured may drive distinct health risks beyond their calorie counts or nutritional labels. A study published in the journal Nature Metabolism examined how the body responds to foods that undergo heavy industrial processing compared with minimally processed meals that contain the exact same amount of calories, carbohydrates, fats, protein, and fiber.

Researchers Measure Metabolic Reactions to Processed Meals

For the study, researchers recruited about 30 healthy adults ages 18 to 45 to eat two nutritionally matched test meals on separate occasions at least three days apart. After fasting overnight, participants entered a sealed chamber to measure their metabolic responses. They had 10 minutes to consume either a minimally processed meal—consisting of a sliced banana, dried cranberries, cheese, and a hard-boiled egg—or an ultra-processed meal, which included a bite of a peanut butter and jelly sandwich, deli turkey, veggie chips, a cookie, cereal, instant mashed potatoes, and water. Blood samples were drawn before the meal and six more times over the subsequent three hours to track metabolism, calorie burn, carbohydrate oxidation, and insulin response. While blood sugar levels remained similar after both meals, blood sugar stayed elevated longer after the ultra-processed food.

Insulin Levels Remain Elevated After Ultra-Processed Food Consumption

The study revealed a sharp difference in how the body handles insulin when foods are heavily processed. Researchers found that insulin levels stayed high between the 40- and 120-minute marks following the ultra-processed meal, whereas insulin levels dropped during that same window after the minimally processed meal. Study co-author Alexandra DiFeliceantonio, PhD, a neuroscientist who focuses on appetite and associate professor at the Fralin Biomedical Research Institute at Virginia Tech in Roanoke, expressed initial surprise at the findings.

I called up the lab and said, Is there something wrong with this data?

Alexandra DiFeliceantonio, PhD

Dr. DiFeliceantonio explained that the increase in insulin may stem from the fact that ultra-processed foods are essentially predigested through high heat and enzymatic degradation, making their nutrients more bioavailable and easier for the body to absorb quickly.

Ultra-Processed Foods May Accelerate Insulin Response

Sandra Zhang, RDN, LDN, a registered dietitian-nutritionist at the Frances Stern Nutrition Center at Tufts Medical Center in Boston, agreed that rapid nutrient absorption likely plays a role in the accelerated insulin response. However, Zhang noted that real-world consumption patterns differ from controlled laboratory settings because ultra-processed foods are engineered to encourage overconsumption.

Ultra-processed foods are often easier to digest, so nutrients may become available more quickly. That can lead to a faster insulin response, although we still don’t know the exact mechanism.

Sandra Zhang, RDN, LDN

Zhang added that people tend to eat greater volumes of these foods in a single sitting, leading to higher blood sugar spikes from increased intake of refined carbohydrates and added sugars. Dr. DiFeliceantonio warned that frequent high insulin responses can raise the risk of insulin resistance and type 2 diabetes over time, though participants in this trial experienced only short-term effects.

Broader Dietary Guidelines Target Added Sugars and Chronic Inflammation

The American Cancer Society Guideline for Diet and Physical Activity for Cancer Prevention also recommends limiting ultra-processed foods and sugar-sweetened beverages to reduce overall health risks. Excess body weight driven by calorie-dense foods is linked to 13 types of cancer, while chronic inflammation resulting from poor diet is tied to colorectal, breast, prostate, and lung cancers. While the American Cancer Society notes that added sugar does not directly trigger cancer on its own, consuming too many processed products contributes to weight gain and inflammation.

Study Limitations Leave Open Questions About Long-Term Metabolic Impact

Study authors acknowledged several limitations, including a relatively small participant pool and differences in protein sources between the test meals that could have influenced insulin secretion. Real-world eating habits involve faster consumption rates and variable caloric intake. As researchers continue to study how food processing alters systemic responses independently of nutritional content, experts suggest focusing on minimally processed foods while enjoying ultra-processed items in moderation.