Scientists compared four different ways of classifying how processed our food is using data from nearly 4,400 American adults. They found that no matter which classification system they used, eating more ultra-processed foods was linked to weight gain, inflammation in the body, and lower intake of healthy nutrients like fiber and protein. The study shows that while different systems classify foods slightly differently, they all reach the same conclusion: eating lots of highly processed foods isn’t great for our health. Researchers say we need one standard way to measure processed foods so everyone can understand the health risks better.

The Quick Take

  • What they studied: Whether different ways of classifying processed foods give similar results when looking at health outcomes
  • Who participated: 4,392 American adults with an average age of 47 years; about half were women, and 63% were white
  • Key finding: All four classification systems showed that eating more ultra-processed foods was connected to higher body weight and markers of inflammation in the blood, even though the systems classified foods slightly differently
  • What it means for you: The type of processed food classification system doesn’t matter as much as the main message: eating fewer ultra-processed foods and more whole foods appears beneficial for weight management and reducing inflammation. However, this is observational research, so we can’t say processed foods definitely cause these problems

The Research Details

Researchers took information from a large national health survey (NHANES) that tracks what Americans eat and their health. They took 4,605 different foods and drinks and sorted them using four different classification systems that scientists use to measure how processed foods are. The four systems were NOVA (from Brazil), IARC (an international cancer research group), IFIC (a food information council), and UNC (University of North Carolina). They then looked at what people ate and compared it to their weight, blood sugar markers, and inflammation levels using statistical analysis that accounted for the survey’s design.

The researchers divided all foods into three groups: minimally processed (like fresh fruits and vegetables), processed (like canned foods with added salt or sugar), and highly processed or formulated (like packaged snacks and fast food). Two different people independently classified the foods to check if the systems were reliable, and they agreed between 68% and 86% of the time.

They then looked at whether people who ate more highly processed foods had different health outcomes than those who ate less, while accounting for age, race, education level, and other factors that might affect the results.

Scientists use different classification systems to study processed foods, which can make it confusing to compare research studies. This study shows whether these different systems give similar answers about health risks. If they do, it suggests the main message about processed foods is consistent. If they don’t, it would mean the choice of system really matters. This helps researchers and policymakers decide if we need one standard system.

This study used real-world data from a nationally representative survey, which is a strength. However, it’s observational, meaning researchers watched what people ate and their health but didn’t control their diets. This means we can see connections but can’t prove that processed foods cause health problems. The inter-rater agreement (68-86%) was reasonable but not perfect, suggesting some foods are harder to classify. The study included diverse participants, which is good for generalizability.

What the Results Show

All four classification systems showed the same pattern: people who ate more highly processed foods had higher body mass index (BMI) and higher levels of C-reactive protein, a marker of inflammation in the blood. This was true across all four systems, even though they classified foods differently.

The systems disagreed on how much food should be classified as highly processed. The IARC system classified the most foods as highly processed, while the IFIC system classified the fewest. This shows that the systems have different standards for what counts as “ultra-processed.”

Regardless of which system was used, the top sources of highly processed foods in people’s diets were grain products (like bread and cereals), meat and poultry mixtures (like processed meats and prepared dishes), and sugars, sweets, and beverages (like soda and candy).

People who ate more highly processed foods also ate less protein, fiber, and important vitamins and minerals. They tended to be younger, have lower education levels, and were more likely to be White or Black.

The study found consistent patterns across demographic groups. Younger adults ate more highly processed foods than older adults. People with lower education levels consumed more highly processed foods. The nutrient deficiencies associated with high processed food intake were consistent across all classification systems, including lower intake of fiber, protein, iron, and various vitamins.

Previous research has linked ultra-processed foods to weight gain and inflammation. This study confirms those findings and adds that the connection holds true regardless of which classification system scientists use. This suggests the health risks of processed foods are real and not dependent on how researchers define them. The study supports growing concern about processed foods in public health.

This study only shows associations, not cause-and-effect relationships. We can’t say that processed foods caused the weight gain or inflammation—only that people who ate more processed foods had these health issues. People reported their own food intake, which can be inaccurate. The study included mostly American adults, so results may not apply to other countries or age groups. The classification systems weren’t perfect at agreeing on which foods were processed, which could affect results slightly.

The Bottom Line

Based on this research, reducing intake of highly processed foods and eating more minimally processed foods like fresh fruits, vegetables, whole grains, and lean proteins appears beneficial for weight management and reducing inflammation. This recommendation has moderate confidence because the evidence is observational but consistent across multiple measurement systems. Consider gradually replacing processed snacks and beverages with whole food alternatives.

This research is relevant for anyone interested in weight management or reducing inflammation. It’s particularly important for people with higher body weight or those at risk for heart disease. People with lower education or income may find this especially relevant since the study showed higher processed food consumption in these groups. This doesn’t apply to people with specific medical conditions requiring processed foods for safety or nutrition.

Changes in weight and inflammation markers typically take 4-12 weeks to become noticeable, though some people may see improvements in energy and digestion sooner. Consistent dietary changes over months and years are needed for significant health improvements.

Want to Apply This Research?

  • Track the number of highly processed food servings consumed daily (grain products, processed meats, sugary beverages) versus minimally processed foods. Aim to reduce processed servings by 25% each week and increase whole food servings by the same amount.
  • Use the app to log meals and identify which highly processed foods you eat most frequently. Set a goal to replace one processed food item per day with a minimally processed alternative (e.g., swap soda for water, packaged snacks for fresh fruit, processed meat for grilled chicken).
  • Track weekly averages of processed versus whole food intake. Monitor body weight weekly and take progress photos monthly. If available, track energy levels and digestion quality as subjective markers of improvement. Set monthly goals to gradually shift the ratio of processed to whole foods.

This research shows associations between processed food consumption and health outcomes but does not prove that processed foods cause these health problems. Individual responses to dietary changes vary. Before making significant dietary changes, especially if you have existing health conditions, take medications, or have food allergies, consult with a healthcare provider or registered dietitian. This information is for educational purposes and should not replace professional medical advice.