Ultra-Processed Foods: What Does Current Research Say?

Few nutrition topics are currently discussed as controversially as ultra-processed foods. While some describe them as a major cause of modern lifestyle-related diseases, others consider the public debate exaggerated and scientifically insufficiently nuanced. In fact, research has made considerable progress in recent years. Numerous large observational studies and the first controlled intervention studies now provide a much clearer picture of how heavily processed foods may affect metabolism, cardiovascular health and long-term disease risks.

The discussion is no longer limited to calories or individual nutrients. Increasing attention is being paid to the effects of industrial processing, food structure and certain additives on the human body. At the same time, it is becoming clear that ultra-processed foods are not automatically unhealthy and that, conversely, unprocessed products are not inherently healthy.

This often creates uncertainty for consumers. What exactly counts as an ultra-processed food? Which health risks are well supported scientifically? And which relationships are still being investigated?

Table of contents

1. What are ultra-processed foods?
2. What characterises ultra-processed foods?
3. Why is research focusing on ultra-processed foods?
4. What do large observational studies show?
5. The Hall study provides an important clue
6. Why do ultra-processed foods often lead to higher energy intake?
7. What role do blood sugar and insulin metabolism play?
8. Ultra-processed foods and the gut microbiome
9. Do food additives play an independent role?
10. What do ultra-processed foods mean for healthy ageing?
11. Are ultra-processed foods inherently unhealthy?
12. What role does the overall dietary pattern play?
13. What does this mean for everyday life?
14. What are the limitations of current research?
15. Conclusion
16. Sources

What are ultra-processed foods?

The term ultra-processed foods does not describe a single food group but rather the degree of industrial processing.

Internationally, the so-called NOVA classification is frequently used for this purpose. It categorises foods according to how extensively they have been processed and which ingredients are used in their production.

The classification comprises four groups:

• unprocessed or minimally processed foods,
• processed culinary ingredients such as vegetable oils or butter,
• processed foods,
• ultra-processed foods.

The fourth category in particular is the focus of current research.

What characterises ultra-processed foods?

Ultra-processed foods often no longer consist primarily of original ingredients but of industrially manufactured components that have undergone numerous processing steps.

Typical characteristics include:

• isolated starches or sugars,
• refined vegetable oils,
• protein isolates,
• emulsifiers,
• stabilisers,
• flavourings,
• colourings,
• sweeteners or flavour enhancers.

They also frequently undergo intensive industrial processing that improves texture, taste, shelf life and marketability.

Typical examples include:

• soft drinks,
• sweets,
• crisps,
• high-sugar breakfast cereals,
• many frozen ready meals,
• instant products,
• flavoured dairy desserts,
• numerous packaged snacks,
• some meat substitutes,
• many industrially produced baked goods.

Importantly, classification does not depend solely on the presence of individual additives. Rather, the NOVA classification takes the entire industrial processing process into account.

However, this also creates grey areas.

Plain yoghurt, for example, is considered a processed food, while heavily flavoured fruit yoghurt containing numerous additives is usually classified as ultra-processed.

Why is research focusing on ultra-processed foods?

For a long time, nutrition science focused mainly on individual nutrients.

Saturated fatty acids, sugar and salt were considered central influences on health. However, this model does not explain all observations.

Two foods can have a similar nutrient composition and still produce different health effects.

An example illustrates this difference.

An apple and sweetened apple juice contain comparable amounts of carbohydrates. However, they differ considerably in their fibre content, cellular structure, satiety effect and the speed at which sugar is absorbed.

This insight has broadened the perspective of research.

Researchers are increasingly investigating whether processing itself may have health consequences.

Several possible mechanisms are being examined:

• altered food structure,
• reduced satiety,
• higher energy density,
• more rapid energy absorption,
• changes to the gut microbiome,
• effects of individual additives,
• effects on metabolism and inflammatory processes.

What do large observational studies show?

Numerous large cohort studies have been published in recent years.

Researchers often follow tens of thousands of people over many years and examine which dietary habits are associated with later diseases.

A consistent pattern is now becoming increasingly clear.

In many studies, high consumption of ultra-processed foods is associated with an increased risk of:

• cardiovascular disease,
• type 2 diabetes,
• obesity,
• high blood pressure,
• certain types of cancer,
• depression,
• all-cause mortality.

The French NutriNet-Santé study became particularly well known.

In this large prospective cohort, a higher proportion of ultra-processed foods in the daily diet was associated with an increased risk of cardiovascular disease. Similar results were later observed in Spain, the United Kingdom, the United States and other countries.

Several meta-analyses combining data from numerous cohort studies have reached comparable conclusions.

However, one important limitation applies.

Observational studies can demonstrate associations but cannot prove clear cause-and-effect relationships.

People who consume large amounts of ultra-processed foods often differ in other areas of their lifestyle. They may exercise less, smoke more frequently or consume more alcohol. Modern studies statistically adjust for these factors, but such influences cannot be excluded completely.

The Hall study provides an important clue

A controlled intervention study conducted by Kevin Hall’s research group at the National Institutes of Health therefore represented an important milestone.

The researchers developed two diets. 

One consisted primarily of ultra-processed foods.

The other consisted primarily of unprocessed or minimally processed foods.

Both diets were designed to contain comparable amounts of calories, fat, protein, carbohydrates, sugar, fibre and sodium.

Participants were allowed to eat as much as they wanted on both diets. 

The result was remarkable.

During the ultra-processed diet phase, participants consumed an average of around 500 additional kilocalories per day. Their body weight increased measurably within two weeks.

During the predominantly unprocessed diet phase, energy intake decreased spontaneously and body weight fell again. 

Because of its short duration, the study could not draw conclusions about long-term disease. However, it demonstrated for the first time under controlled conditions that ultra-processed foods appear to possess characteristics that increase spontaneous energy intake.

Why this occurs is currently being investigated intensively.

Why do ultra-processed foods often lead to higher energy intake?

The Hall study answered one important question but left another unanswered.

Why do people often eat more ultra-processed food even when nutrient composition is comparable?

Current research assumes that several mechanisms operate simultaneously.

Reduced satiety

Many ultra-processed foods have a soft texture and can be eaten quickly.

This allows larger quantities of food to enter the stomach within a short period before hormonal satiety signals have fully taken effect.

Hormones such as GLP-1, peptide YY (PYY) and cholecystokinin (CCK) require time to exert their effects after a meal. If food is consumed very quickly, energy intake may already be considerably higher before the brain receives a sufficient satiety signal.

In the Hall study, participants did in fact eat more quickly during the ultra-processed diet phase than during the unprocessed diet phase.

High energy density

Many heavily processed products contain large amounts of fat while containing little water or fibre.

This increases their energy density, meaning the number of calories per gram of food.

For comparison:

100 grams of vegetables often provide fewer than 40 kilocalories.

100 grams of crisps, by contrast, often contain more than 500 kilocalories.

The more energy-dense a food is, the easier it becomes to consume a large number of calories before sufficient satiety develops.

Fibre and food structure

Metabolism is influenced not only by ingredients themselves but also by their physical structure.

In unprocessed plant foods, carbohydrates, fats and secondary plant compounds are embedded in complex cellular structures.

These structures must first be broken down during chewing and digestion.

Many ultra-processed foods lose this natural matrix during industrial processing.

As a result, nutrients become available more quickly and are often absorbed more rapidly.

Research refers to this phenomenon as the food matrix. It is now considered an important factor in satiety, blood sugar regulation and metabolism.

What role do blood sugar and insulin metabolism play?

Ultra-processed foods differ considerably in composition. 

Many products contain large amounts of rapidly available carbohydrates. 

As a result, blood sugar often rises more rapidly after eating than it does after fibre-rich whole grains, legumes or vegetables.

The body responds by releasing more insulin.

Insulin enables glucose uptake into muscle and adipose tissue and thereby lowers blood sugar again.

In the short term, this is a normal physiological process. 

A persistently high burden of readily available energy can become problematic, particularly when combined with chronic calorie excess, physical inactivity and excess weight.

Over time, metabolic changes may develop that increase the risk of insulin resistance. 

However, not every ultra-processed food automatically has a high glycaemic effect. There are considerable differences within this food group.

Ultra-processed foods and the gut microbiome

Another area of research examines how industrial processing affects the gut microbiome.

A low-fibre diet is considered one of the most important factors capable of reducing the diversity of gut bacteria.

Because many ultra-processed foods contain only small amounts of fermentable fibre, the composition of the microbiome often changes as well.

Among other effects, this reduces the production of short-chain fatty acids such as butyrate.

These metabolites support the intestinal barrier, regulate the immune system and influence energy metabolism.

In addition, several additives are currently being studied intensively.

Emulsifiers in particular are the focus of experimental studies.

Animal models show that certain emulsifiers can alter the intestinal mucus layer and promote inflammatory processes. 

However, it has not yet been conclusively established whether these findings can be transferred to humans to the same extent.

The available human studies provide indications of possible effects but are not yet sufficient to make general statements about individual additives.

Do food additives play an independent role?

It is often assumed that all health risks associated with ultra-processed foods are caused by additives.

The scientific evidence does not support such a simple explanation.

Additives perform different functions.

For example, they improve:

• shelf life,
• texture,
• colour,
• taste,
• stability.

Many additives have undergone extensive toxicological testing and are considered safe within approved maximum levels.

At the same time, the health effects of some substances continue to be investigated.

Those currently discussed most intensively include:

• certain emulsifiers,
• some artificial sweeteners,
• nitrite curing salt in processed meat.

However, none of these substances alone can explain the entirety of the observed associations between ultra-processed foods and chronic diseases.

The risk probably arises from the interaction of several factors, including high energy density, low fibre intake, altered food structure, overconsumption and individual components of industrial processing.

What do ultra-processed foods mean for healthy ageing?

From the perspective of longevity research, it is particularly interesting that many biological processes influenced by a persistently unfavourable diet are also among the hallmarks of ageing.

A chronic energy surplus can promote inflammatory processes, reduce metabolic flexibility and worsen insulin sensitivity.

At the same time, mitochondrial performance often declines while oxidative stress increases. 

These changes do not develop as a result of individual meals.

Rather, they arise when more energy is consumed than the body uses on a regular basis over many years. 

A diet consisting mainly of unprocessed or minimally processed foods often makes it easier to consume fibre, micronutrients and secondary plant compounds. At the same time, many people find it easier to match their energy intake to their actual requirements.

Whether ultra-processed foods also directly influence independent ageing processes is currently being investigated intensively.

Are ultra-processed foods inherently unhealthy?

Current evidence argues against a simple division into “healthy” and “unhealthy”.

The NOVA classification describes the degree of processing, not automatically the health value of a food.

Some ultra-processed products can offer nutritional advantages. Examples include certain whole-grain products, unsweetened plant-based alternatives to dairy products, fortified foods and some meat substitutes with a favourable nutrient composition.

Conversely, not all minimally processed foods are automatically healthy. Large amounts of butter, sugar or red meat are not classified as ultra-processed foods but should likewise not be consumed without limitation.

The degree of processing alone is therefore insufficient for assessing a food.

Several factors are decisive:

• overall nutrient composition,
• fibre content,
• energy density,
• the food matrix,
• portion size,
• its role within the overall diet.

Scientific evidence supports considering the degree of processing as additional information rather than as the sole quality criterion.

What role does the overall dietary pattern play?

People do not consume isolated foods but complete dietary patterns.

Modern nutrition studies therefore increasingly examine the entire diet rather than individual products.

The Mediterranean diet and various plant-focused dietary patterns are among the best studied.

Despite differing in detail, they share several characteristics:

• a high proportion of vegetables and fruit,
• regular consumption of legumes,
• whole-grain products as an important source of carbohydrates,
• nuts and seeds,
• high-quality plant fats,
• predominantly unprocessed or minimally processed foods.

Interestingly, many of the observed health benefits do not result from individual so-called superfoods but from the interaction of numerous foods.

Fibre supports the gut microbiome. Unsaturated fatty acids influence fat metabolism. Secondary plant compounds have antioxidant and inflammation-modulating effects. At the same time, the natural food matrix often promotes better satiety.

This combination can hardly be reproduced completely through individual food supplements or isolated nutrients.

What does this mean for everyday life?

Scientific evidence now provides a comparatively clear message.

Health is determined not by individual products but by long-term dietary behaviour.

Occasionally eating frozen pizza, chocolate or crisps does not automatically increase disease risk. Problems arise mainly when ultra-processed foods consistently make up the largest proportion of the daily diet while displacing fibre-rich, nutrient-dense foods.

In practical terms, this means:

• Vegetables and fruit should be a regular part of the daily diet.
• Whole-grain products and legumes provide fibre and promote long-lasting satiety.
• Heavily processed snacks and sugary drinks should remain the exception.
• Home-prepared meals often make it easier to select a balanced range of foods.
• Foods should be assessed according to their overall nutritional value rather than solely by their degree of processing.

This approach is not only well supported scientifically but also realistic to implement over the long term.

What are the limitations of current research?

Although the evidence base has improved considerably in recent years, questions remain unanswered.

One major criticism concerns the NOVA classification itself.

Some researchers argue that foods with very different nutritional quality are sometimes assigned to the same category. As a result, products with a favourable composition may be evaluated together with clearly unfavourable foods.

In addition, although observational studies show consistent associations, they cannot prove clear causality.

The Hall study provides important experimental evidence but examined a period of only two weeks. Conclusions about long-term disease risks cannot be drawn directly from it.

It also remains unclear which characteristics of ultra-processed foods have the greatest influence.

Possible factors include:

• high energy density,
• rapid eating speed,
• the altered food matrix,
• low fibre content,
• individual additives,
• changes to the gut microbiome,
• combinations of these mechanisms.

There is probably no single cause. Rather, the available data suggest that several biological processes contribute simultaneously to the observed relationship.

Future intervention studies will be crucial for understanding these mechanisms better and assessing the role of individual food groups more precisely.

Conclusion

Ultra-processed foods are among the most intensively studied topics in modern nutrition research. Current evidence consistently shows that a high proportion of these foods in the diet is associated with an increased risk of obesity, type 2 diabetes, cardiovascular disease and higher all-cause mortality. At the same time, the controlled Hall study provides important evidence that ultra-processed foods can increase spontaneous energy intake. 

Nevertheless, it would not be scientifically correct to attribute all health risks exclusively to the degree of processing. What matters is the interaction of several factors. Energy density, fibre content, the food matrix, satiety, eating speed and long-term dietary habits influence metabolism together.

This distinction is also important for healthy ageing. A diet consisting mainly of unprocessed or minimally processed foods provides fibre, high-quality fats, vitamins, minerals and secondary plant compounds. At the same time, it supports a healthy body weight, a diverse gut microbiome and stable metabolic health. Many of these effects act on biological processes closely associated with the hallmarks of ageing.

For everyday life, this does not mean striving for perfection. Individual ultra-processed foods are not automatically problematic. What matters is the proportion they consistently make up within the overall diet. The more frequently fresh, nutrient-rich foods shape the menu, the easier it becomes to follow a dietary pattern that supports both current health and healthy ageing over the long term.

Sources

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