Processed vs Ultra-Processed Foods: Nuances Matter for Sound Advice

Inside: Is the choice of processed vs ultra-processed foods key to healthy eating? Broad categories of foods might seem to simplify advice, but a closer look at the research shows that they sometimes over-simplify choices and can add confusion instead of clarity.

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Have you ever played, “One of These Things is Not Like the Others?”   

It’s a brain-teaser game made popular on Sesame Street®. But with adjustments in the questions, it can prompt much deeper analytical thinking among people of all ages.

In the simple version, you show kids four things, and one of them is different from the other three in some way. For example, you might show 3 numbers and 1 letter, 3 different sized rectangles and 1 circle, or 3 things that are red and 1 that’s blue. Then you prompt the child to pick out which one doesn’t fit with the others.

What does this Sesame Street game have in common with Sherlock Holmes and advice about processed foods in a healthy diet?  🤔

Sherlock Holmes was famous for combining inductive reasoning (using individual observations to develop an overall theory) and deductive reasoning (using the general statement to make a conclusion about individual circumstances) to solve puzzling “who-dunnit” challenges.

Dietitians are often asked about choosing healthy foods.

Books, blogs and other media are often quick to provide simple answers by categorizing foods as either “good” or “bad”.

• High vs low in fiber, vitamins, or sodium
• Plant-based vs animal-based
• Minimally processed vs processed vs ultra-processed…. This is the hot topic in online discussions and professional conferences alike right now.

But just as the “lesser” detectives in Sherlock Holmes stories found, jumping to conclusions based on dividing food into categories without awareness of important nuances may lead you off track.

The dietitian’s challenge: What advice do we give about whether avoiding ultra-processed foods and sticking with minimally processed foods is the answer for healthy eating?

Almost all food is processed in some way. The real debate is about commercially processed foods… specifically those that are more highly processed – often called “ultra-processed” foods.

Are Ultra-Processed Foods Always a Poor Choice?

A few key points are behind much of the conflicting information about processed vs ultra-processed foods.

• Amount and purpose of processing is the basis for classifying a food as ultra-processed, say the researchers who developed the NOVA system.
  • Although a food’s classification may have implications for nutrient content, nutritional value does not define whether a food is or is not ultra-processed.
• Ultra-processed foods are often more concentrated in calories and lower in fiber and nutrients than minimally processed foods. But not always.
  • High calories stem from added sugars and fats, sometimes multiple kinds of them, that are often high — especially compared to similar portions of minimally processed foods.
  • You can’t identify these foods based on nutrients on the Nutrition Facts label, because fortification and addition of isolated forms of protein or fiber can boost content in ultra-processed foods.
• What’s on the ingredient list — not the number of ingredients — defines an ultra-processed food. A list of 5 or more ingredients is common in an ultra-processed food, but doesn’t define one.

Ultra-Processed Foods and Weight Gain: What Research Really Shows

Many studies link greater weight gain in adults with:

• Higher consumption of French fries, chips, and sugar-sweetened beverages
• Lower consumption of vegetables, fruits, and whole grains

But does high consumption of ultra-processed food as a whole category cause weight gain and obesity?

Cross-sectional studies provide much of the early evidence linking ultra-processed foods and obesity. For example, one often-cited study categorized diets of over 15,000 US adults based on the percent of calorie consumption that came from ultra-processed foods and foods that weren’t ultra-processed.

• On average, ultra-processed foods accounted for 56.1 % of total calories. Those in the top 20% of ultra-processed food consumption got at least 74.2% of calories from these foods. Among people with lowest consumption, ultra-processed foods accounted for about 25% of calories.
• People in the group with highest ultra-processed food consumption had highest BMI (body mass index, a way of expressing weight for height), largest waist size, and the greatest prevalence of overweight, obesity, and abdominal obesity. (Abdominal obesity was defined here using standard definitions equivalent to at least 40 inches in men and at least 35 inches in women.) And that’s after adjusting for demographic details and factors like physical activity that can be associated with obesity.
• But ultra-processed foods can’t be the whole answer to excess weight. Even among the people with lowest consumption of ultra-processed foods, BMI defined 65% as having overweight and 31% with obesity, and 48% met criteria for abdominal obesity.

Although cross-sectional studies like this can show that ultra-processed food consumption tends to be higher in people with obesity, they can’t show whether consuming more ultra-processed food actually led to weight gain.

Prospective studies that follow people across time now also tie changes in weight, waist and BMI to ultra-processed food consumption. Overall, these studies show that those who get the greatest part of their diets from ultra-processed foods are more likely to develop overweight or obesity, and if they already have overweight, to develop obesity, compared to people who consume the lowest amounts of these foods. For example:

• Ultra-processed foods accounted for 71.5% of calories among top consumers in a study that followed more than 22,000 UK adults for 5.6 years. Compared to the lowest consumers of ultra-processed food (about 25% of total calories), these high consumers showed: 79% increase in risk of obesity, 30% increase in risk of abdominal obesity, and 14% increase in risk of gaining at least 5% body fat. And analysis shows these changes were consistent regardless of people’s starting BMI.
• A study in Spain that followed people for almost 9 years also links higher consumption of ultra-processed foods with development of overweight and obesity. People who included about 6 servings a day of ultra-processed foods were 26% more likely to develop overweight or obesity than people with lowest intake, who averaged 2.7 servings a day. This association was not related to BMI at the start of the study.
• Not all studies include information about which specific ultra-processed foods predominate in participants’ diets. However, among the studies that provide this information (often in a supplementary file), people with higher consumption of ultra-processed foods generally ate diets with more sugar-sweetened beverages, French fries, fast food, commercial desserts (candy, cookies, cakes), processed meats, packaged salty snack foods, and ready-to-eat/heat meals.

A randomized controlled trial designed to provide insights on this has gotten a lot of attention. Twenty weight-stable adults lived in the research facility, giving researchers complete control over their access to foods. Participants spent two weeks on a diet with 83% of calories as ultra-processed foods (the amount in top consumers in the prospective studies) and another two weeks on a diet with no ultra-processed foods. Instructed to consume as much or as little as they wanted, they were provided with 3 meals/day and had access all day to snacks appropriate for their assigned diet.

• Not just “snack food all day”. What’s unique about this study is that the diets high and low in ultra-processed foods were designed to be matched for the calories available, total sugar, carbohydrate, fat, protein, and fiber. The diet high in ultra-processed foods included prepared canned and frozen main and side dishes, as well as chips and desserts. However, sugar in the diet high in ultra-processed foods included far more added sugars rather than naturally occurring sugars. And to ensure equal amounts of fiber, the diet high in ultra-processed foods relied on a fiber supplement.
• People consumed an extra 500 calories a day on the diet high in ultra-processed foods. And weight changes reflected that, as people gained about 2 pounds in 2 weeks when ultra-processed foods were high and lost about 2 pounds in 2 weeks when diets didn’t include ultra-processed foods.
• Faster eating – but not perception of better taste or more hunger – was tied to the greater calorie consumption and weight gain on the diet high in ultra-processed foods.

Ultra-Processed vs Minimally Processed Foods: What Explains the Weight Gain?

A diet high in ultra-processed foods does seem likely to promote weight gain. But to determine whether all foods that meet the ultra-processed criteria promote obesity – or only certain ones do – it’s important to understand what’s behind the link to weight gain. Research has identified several potential reasons for this association.

• Concentrated source of calories: Many ultra-processed foods are what’s called calorie-dense, which means that even in a relatively small portion, calorie content is higher than in unprocessed and minimally processed foods. Your feelings of fullness are more sensitive to portion size than to calorie content, so these calorie-dense foods make it easy to consume more calories than you need.
  • Not all ultra-processed foods are calorie-dense, though. Unsweetened soy milk, for example, can be comparable to skim milk in calories, and a veggie burger can be comparable or lower in calories than a hamburger classified as minimally processed.
• Higher glycemic index/load: Many ultra-processed foods are lower in fiber and higher in sugar. And they may even be processed in a way that makes the carbohydrate so easy to digest quickly that they cause rapid rises in blood sugar after eating. Some researchers suggest that the resulting higher levels of insulin could promote weight gain, and the rapid rise and then fall in blood sugar could promote greater hunger.
  • But does this apply to all ultra-processed foods? For example, in a cross-sectional study of US adults, ultra-processed foods were more likely to promote weight gain in women – whose ultra-processed selections were more likely to reflect eating more sweets – than in men (in whom ultra-processed foods were more likely meats and other savory foods).
• Structural changes to the food: When ultra-processing creates changes in texture and structure of the food matrix, it may do more than increase carbohydrate digestibility and rise in after-meal blood sugar. Some researchers suggest that these changes could cause these foods to be consumed more quickly than minimally processed foods. And as sensory awareness of the food and eating experience decrease, this could reduce or delay satiation and promote eating beyond calorie needs.
  • But ultra-processed foods vary in how their texture and structure are altered. For example, a randomized controlled trial created 4 meal types: ultra-processed, hard-textured; ultra-processed, soft-textured; minimally processed, soft-textured; and minimally processed, hard-textured. On average, people ate 300 fewer calories from the “hard minimally processed” meal than from the “soft ultra-processed” meal. But people consumed fewer total calories and fewer calories per minute from both “hard-textured” meals than from “soft-textured” meals, regardless of whether they were ultra-processed or minimally processed.
• Engineered to be hyper-palatable: Many ultra-processed foods are produced with high levels of fat, salt, sugar, and artificial flavors. Some researchers suggest that flavors may even be specifically designed to be so palatable that they override our bodies’ mechanisms to detect fullness and hunger.
  • However, evidence does not show this “hyper-palatability” effect for all ultra-processed foods, such as plant-based dairy and meat alternatives.
• Maybe it’s not the ultra-processed foods themselves, but how we access them: When foods are available in convenience stores and vending machines 24/7, packaged in large portion sizes, accessible on an impulse with no cooking needed, cheaper, and aggressively marketed for all-day snacking, it’s easy for those foods to promote overeating and displace less-processed foods.
  • But this doesn’t make sense for all ultra-processed foods. For example, whole wheat bread that’s commercially produced seems unlikely to promote overeating more than an artisanal or homemade white bread (which would be classified as processed, but not ultra-processed).

Ultra-Processed Foods: What About Cancer and Heart Health?

It’s no surprise when eating habits that promote excess weight gain lead to increases in hypertension, metabolic syndrome, cardiovascular disease risk, and risk of obesity-related cancers. That’s especially true when weight gain occurs largely as abdominal fat, which can mean increases in visceral fat that promote inflammation and insulin resistance.

But does your choice of minimally processed and processed vs ultra-processed foods influence heart health and cancer risk even beyond effects on weight gain?

Far fewer studies look at these outcomes than at obesity and weight gain. And they’re even harder to interpret clearly.

Ultra-Processed Foods: Risk to Cardiovascular Health?

Cross-sectional studies: In a large cross-sectional study of US adults (NHANES), compared to people with the smallest proportion of their diet coming from ultra-processed foods, people with highest consumption were 19% more likely to have hypertension and 28% more likely to have metabolic syndrome. [That was after adjusting for demographic and lifestyle factors related to CVD risk, but not other aspects of diet.]

• Analysis combining the US study with results of a cross-sectional study in a particular indigenous population in Canada found no association of ultra-processed foods with hypertension, but a strong link to having metabolic syndrome.
• Just as in the studies on weight gain, these studies cannot prove that ultra-processed food consumption increased before development of hypertension or metabolic syndrome.
• These studies compare highest to lowest consumption of ultra-processed foods. Here, people with more than 70 or 80 percent of total calories from these foods were compared to people whose diets included them as less than 40 percent of calories in the US study, 21 percent in the Canadian study. The studies don’t tell us anything about associations with typical consumption.

Prospective cohort studies: The UK Biobank study followed a large population of adults for about 11 years. Top consumers of ultra-processed foods were more likely to develop heart disease (both CHD and CVD) than people who consumed the least of these foods. In the ARIC study, which followed a large population of middle-aged US adults for up to 32 years, people with highest consumption of ultra-processed foods were more likely to develop or die from heart disease (CAD).

• These associations were seen regardless of BMI and presence of hypertension or diabetes.
• Increased risk was not only comparing highest vs lowest consumption. Analysis shows each increase in ultra-processed food consumption — especially of 4 or more servings/day — linked to further increased risk.
• Analyses combining results of other prospective cohort studies also show increased risk of developing hypertension and greater cardiovascular disease risk or mortality. However, these analyses only compare highest versus lowest intake; they do not identify whether average intake is linked to risk.

Ultra-Processed Foods and Cancer: What Does Research Show?

Studies are even more limited and less clear-cut on links of ultra-processed foods to cancer risk.

Here are examples of three key prospective cohort studies that show an association between consuming more ultra-processed foods and increased risk of developing at least some forms of cancer or of dying from cancer. But inconsistencies in results or these and other studies leave a lot of questions.

A prospective cohort study in France followed people for about five years. Compared to people who consumed the least ultra-processed foods, those with highest consumption had greater risk of cancer overall and of postmenopausal breast cancer (but not prostate or colorectal cancer).

• Associations with cancer were seen even after adjusting for BMI, alcohol, total calorie consumption, and scores for diet quality.
• Analysis looking beyond highest vs lowest consumption showed that each 10% increase in the proportion of the diet coming from ultra-processed foods contributed to an association with greater cancer risk.

A headline-making prospective cohort study in the UK followed people for about 10 years. Those who consumed the largest amount of ultra-processed food had a 7% greater risk of developing any type of cancer compared to people who consumed the least. (Risk increased for lung and brain cancer and one specific type of Non-Hodgkin lymphoma, but not for breast, colorectal, or 22 other cancers.)

• Beyond comparisons of highest to lowest consumption, each 10% increase in ultra-processed food was associated with a 2% increase in overall cancer risk.
• This association remained after adjusting for smoking, physical activity, BMI, and other known risk factors.
• Each 10% increase in consumption was linked with a 19% increase in risk of ovarian cancer and with greater deaths from cancer overall and from breast or ovarian cancer. This is the first study to show a link to ovarian cancer, and it generated a lot of media attention. That’s partly because research hasn’t been able to consistently identify any aspect of diet or physical activity that reduces risk of this cancer. However, other researchers emphasize that this study included a small number of ovarian cancer cases, and since it’s a new finding, we need to see if this is repeated in other studies before assuming there is a true link.

Analysis combining three large US cohorts followed participants for about 25 years. Men in the top 20% of ultra-processed food consumers had higher risk of developing colorectal cancer compared to men who consumed the least. Yet women showed no association with overall colorectal cancer risk or any colon subsite. Another study in these cohorts found that higher consumption of ultra-processed foods was associated with greater risk of colorectal polyps (including high-risk types of these colorectal cancer precursors) in both men and women.

• Among men, the association with colorectal cancer remained even after adjusting for BMI, diet quality (both Western pattern indicating an unhealthy diet and the AHEI score for a healthy diet).
• Ultra-processed foods did not all show the same association with colorectal cancer risk. For men, risk was specifically linked with higher consumption of sugar-sweetened drinks and with animal protein-based ready-to-eat products (such as bacon, meat or poultry hotdogs, sausage, lunch meat, and breaded fish sticks).
• Even though overall ultra-processed food consumption wasn’t associated with colorectal cancer risk in women, higher consumption specifically of ready-to-eat or heat mixed dishes (such as pizza, canned soup soup, and French fries) was associated with greater colorectal cancer risk compared to women with lowest consumption of these foods.

Some researchers suggest that ultra-processed foods could uniquely affect cancer risk through compounds formed during industrial processing or transferred from plastic packaging, or through additives that affect the gut microbiota. But we need to remember that these are hypotheses that need to be tested.

It’s still not clear which ultra-processed foods pose cancer risk beyond the foods that evidence-based recommendations already identify for limited consumption – sugar-sweetened drinks, processed meats, “fast foods” and those processed foods that are high in added fat/salt/sugar and low in fiber/nutrients.

How to Make Sense of Processed vs Ultra-Processed Foods in Healthy Eating

With so much evidence linking diets high in ultra-processed foods with undesirable health outcomes, does this mean that we can simplify advice about choosing healthy foods by simply recommending that people avoid ultra-processed foods?

This is where your Sherlock Holmes-type skills come into play — be cautious about using deductive reasoning to draw conclusions prematurely.

Ultra-Processed Foods and Diet Quality: Causal or Confounding?

One reason that studies find high consumption of ultra-processed foods associated with health risks is that this can be a marker of a poor-quality dietary pattern.

Look closely at what foods people in the observational studies with diets high in ultra-processed foods are eating.

Analysis of cross-sectional studies of what US adults eat (NHANES data) shows that as the proportion of calories in diets overall increases:

• Consumption decreases of fiber; protein; vitamins A, C, D, and E; potassium, magnesium, and calcium.
• Levels increase for carbohydrate, saturated fat, and added sugars.
• Scores for dietary quality decrease.

But observational studies simply observe the foods people choose.

In cross-sectional and prospective observational studies, in the US and in other countries, the foods that predominate when a diet is high in ultra-processed foods are sugar-sweetened beverages, sweet bakery (cookies, cakes, pies), fast food, and frozen and shelf-stable meals.

Other examples of ultra-processed foods – such as breakfast cereals, bread, dairy products, and bread – each account for less than 10% of calories in the average diet that’s high in ultra-processed foods.

Sodium? It’s Processed Foods, Not Just Ultra-Processed Foods.

Analysis of diets high in ultra-processed foods show they often exceed recommended limits on sodium consumption, but generally no more so than diets lower in this category of foods.

That’s because even without a lot of ultra-processed foods, diets high in processed foods send sodium intake high.

• Processed meats are a primary example. Bologna, hot dogs, sausages made with non-culinary additives, and reconstituted meat products are grouped as ultra-processed foods. But meats preserved by salting, pickling, curing, or smoking — without preservatives, synthetic flavor enhancers or extracts — are processed (not ultra-processed) foods. Research showing that processed meat consumption increases risk of colorectal cancer includes all these forms of processed meats.
• Other processed foods are also substantially higher in sodium than minimally processed foods. Vegetables in brine or canned with added salt contain more than fresh or frozen vegetables. Even natural cheese, with half the sodium of processed cheese, has double the sodium of getting the same amount of protein from yogurt or milk. And while commercial (ultra-processed) bread is a little higher in sodium than a homemade or artisanal bread, both contain more than an intact whole grain like brown rice, bulgur or quinoa prepared without salt.

Overall diet quality — which is tied to better health in many studies — depends on what you do eat as well as what you avoid.

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How to Use Today’s Research to Create Healthy Eating Habits that Work for You

Step One: Revise your all-or-nothing thinking about processed foods.

• The average US adult gets 57% of calories from ultra-processed foods.
• Studies comparing people with high vs low consumption of ultra-processed foods are usually comparing people who get 75 to 80% of their calories from these foods to people with these foods supplying about 25% to 33% of their total calories.
• The greatest concern is for people who routinely include ultra-processed foods as a substantial portion of daily food choices. — Some evidence shows a modest increase in risk of weight gain or poor health outcomes with each 10% increase in the proportion of the diet coming from ultra-processed foods. In such studies, each stepwise reduction in use would be associated with some risk reduction.

However, the greatest concern is for people who routinely include ultra-processed foods as a substantial portion of daily food choices… and likely depends on which ultra-processed foods are chosen.

Step Two: Focus on the Nuances Among “Processed Foods” that Matter

Studies show that people consuming diets high in ultra-processed foods are more likely to gain weight and develop health problems. But we can’t assume that every choice that meets criteria as an ultra-processed food poses risk. They’re not all the same.

• If you’re cutting down on ultra-processed foods, be selective. Swap out foods and drinks that are concentrated in calories and low in fiber and nutrients for better choices. Make minimally processed foods that are fiber- and nutrient-rich the focus of meals and snacks. – Based on the research reviewed here, calorie density and fiber may not be the whole answer to the downsides of ultra-processed foods, but the big picture of overall research shows that this provides a solid foundation.
• Consider overall content of foods, not just a few nutrients on the label. An ultra-processed food that appears high in fiber because of added sources of isolated fiber can contribute valuable fiber (such as viscous fiber that can help when cholesterol won’t go down). But it can’t replace all the nutrients, protective phytochemicals, and prebiotic compounds you get from making whole grains, vegetables, fruits, and beans a major part of each meal.
• Limit ultra-processed and processed foods high in sodium. This crucial step to combat the toll that high blood pressure is taking requires more than avoiding ultra-processed foods. Check here for more about some simple sodium-cutting tweaks.

Step Three: Choose Processed & Unprocessed Foods that Make a Healthy Dietary Pattern Work for You

A healthy diet has room for some processed foods, and even some ultra-processed foods. But be selective.

• What foods truly add joy to your day? Include modest amounts of those that are less healthful and find alternatives for the ones you’re eating just because they’re close at hand or out of habit.
• What are your biggest barriers to healthy eating habits? Select the processed foods that can make a healthy diet doable for you. If you’re low on vegetables, fruits, whole grains, and beans, then choose the forms that you can most realistically include as replacements for what you’re eating now. But remember that ultra-processed foods aren’t the only way to make healthy quick and easy. Canned pulses and vegetables, quick-cooking whole grains and frozen fruit are valuable when time is tight.
• Priorities among choices are individual. If you’re used to eating a doughnut, whole grain cereal is an upgrade, even if it’s ultra-processed. If you don’t want to or can’t afford the time or money for homemade or artisanal bread, whole grain commercial bread is a sound choice, even though categorized as ultra-processed. Yes, plain yogurt topped with fresh or frozen fruit is optimal, but don’t equate fruit-flavored (sweetened) yogurt with cookies. Especially for people short on time, energy, or cooking facilities, choices like veggie burgers, reduced-sodium canned soup (doctor it up with extra beans and vegetables!) and commercial tomato sauce can support an overall healthy diet.

If your diet is high in ultra-processed foods, health benefits you get by reducing amounts depend on what you choose to replace them. This is a chance to include more whole grains, vegetables, fruits, beans, and nuts, for example. Or you may want to start by replacing sugar-sweetened soft drinks and super-sweetened tea and coffee beverages with water and unsweetened drinks.