What are the side effects of eating processed foods?

October 14, 2025 •

4 min read

According to a 2019 study published in Cell Metabolism, people on an ultra-processed diet consumed an average of 500 more calories per day compared to an unprocessed diet, leading to rapid weight gain. This highlights just one of the many negative consequences that answer the question: What are the side effects of eating processed foods?

Quick Summary

The consumption of processed foods is linked to numerous health issues, such as weight gain, chronic inflammation, and poor gut health, increasing the risk of diseases like diabetes and heart disease.

Key Points

Weight Gain: Processed foods are calorie-dense and low in nutrients like fiber, leading to overconsumption and weight gain.
Chronic Inflammation: The high content of sugar, unhealthy fats, and certain additives in processed foods can trigger a state of chronic low-grade inflammation.
Gut Health Disruption: Additives like emulsifiers and a lack of fiber in ultra-processed foods harm the gut microbiome and increase intestinal permeability.
Nutrient Deficiencies: Diets high in processed foods often lack essential vitamins, minerals, and fiber found in whole foods.
Increased Disease Risk: Regular consumption of ultra-processed foods is linked to a higher risk of developing chronic conditions such as type 2 diabetes, heart disease, and certain cancers.
Mental Health Impacts: Processed food intake is correlated with negative mental health outcomes, including an increased risk of anxiety, depression, and cognitive decline.

Understanding the Spectrum of Processed Foods

Processed foods exist on a spectrum, with varying degrees of alteration from their natural state. The NOVA classification system categorizes foods into four groups based on their processing level:

Unprocessed or Minimally Processed Foods (Group 1): These are foods like fruits, vegetables, eggs, and nuts that are in their natural state or have undergone minimal changes such as cleaning or freezing.
Processed Culinary Ingredients (Group 2): Ingredients like oils, butter, sugar, and salt, derived from Group 1 foods.
Processed Foods (Group 3): Made by combining foods from Groups 1 and 2, these include items like canned vegetables, cheese, and fresh bread.
Ultra-Processed Foods (Group 4): These are industrial formulations often containing many additives and little to no whole food, such as sugary drinks, packaged snacks, and processed meats. These are the types of processed foods most commonly associated with negative health outcomes.

The Extensive Side Effects of Processed Foods

Regular consumption of ultra-processed foods (UPFs) is linked to a variety of health problems. Their composition often encourages overconsumption and negatively impacts the body in multiple ways.

Weight Gain and Obesity

UPFs contribute to weight gain and obesity due to their high caloric density and low levels of protein and fiber, which are important for feeling full. They are often designed to be highly palatable, making it easy to eat large amounts without feeling satisfied. Studies have shown that diets high in processed foods can lead to increased calorie intake and subsequent weight gain.

Nutritional Deficiencies

Diets dominated by UPFs often lack essential vitamins, minerals, and fiber because they displace more nutrient-rich whole foods. The processing methods used to create these foods strip away natural nutrients, and while some are fortified, this doesn't fully replace the nutritional complexity of whole foods. This can be particularly problematic for children.

Chronic Inflammation

Processed foods are a significant contributor to chronic low-grade inflammation, a state linked to many chronic diseases. This is partly due to the high amounts of added sugars and omega-6 fatty acids often found in UPFs. Furthermore, the negative impact of UPFs on gut health can also trigger chronic metabolic inflammation.

Damage to Gut Health

Processed foods can disrupt the balance of microorganisms in the gut, which are vital for health. Diets high in UPFs are associated with reduced microbial diversity and lower levels of beneficial bacteria. Food additives, such as emulsifiers, may also negatively impact the intestinal lining, potentially increasing intestinal permeability and contributing to inflammation.

Increased Risk of Chronic Diseases

Consuming processed foods frequently is associated with an elevated risk of developing serious long-term health conditions:

Cardiovascular Disease: High intake is linked to an increased risk of heart disease, heart attacks, and strokes, partly due to the high sodium, unhealthy fats, and inflammatory effects.
Type 2 Diabetes: The high sugar content and glycemic load in many UPFs can lead to insulin resistance over time.
Certain Cancers: Some studies suggest a link between high UPF intake, particularly processed meats and sugary drinks, and an increased risk of certain cancers, including colorectal cancer. For more information, the World Cancer Research Fund provides findings on this topic: Ultra-processed foods linked to increased cancer risk.

Mental and Cognitive Health Issues

Emerging research indicates a connection between consuming processed foods and negative mental and cognitive health outcomes. This may be related to inflammatory responses and effects on the gut-brain axis. Studies have shown correlations between UPF intake and an increased risk of depression and a faster rate of cognitive decline.

Making Healthier Dietary Choices

While completely eliminating processed foods can be challenging, particularly for those with limited resources, making informed substitutions can significantly improve health.


Feature	Ultra-Processed Food	Healthier Alternative (Minimally Processed)
Convenience Snack	Bag of potato chips, packaged cookies	Handful of nuts, fresh fruit, homemade trail mix, air-popped popcorn
Breakfast	Sugary cereal, pre-packaged muffin	Rolled oats with fresh berries, eggs, plain Greek yogurt
Drinks	Soda, fruit juice with added sugar	Infused water, green tea, homemade smoothie
Meals	Frozen pizza, microwaveable dinner	Homemade pizza with whole wheat dough, roasted chicken with vegetables
Meat	Hot dogs, salami, bacon	Lean chicken, fresh fish, lentils

To reduce your intake of processed foods, consider these tips:

Read Labels: Pay attention to ingredient lists for additives, high levels of added sugar, and sodium to identify UPFs.
Cook at Home: Preparing meals from scratch allows you to control ingredients.
Focus on Whole Foods: Build your diet around fruits, vegetables, whole grains, and lean proteins.
Prioritize Fiber: Increase fiber intake to support gut health and satiety.
Stock Healthy Snacks: Keep nutritious snacks readily available.

Conclusion

The convenience of processed foods comes with significant health costs, including weight gain, chronic inflammation, and negative impacts on gut and mental health. By understanding the different types of processed foods and making conscious decisions to include more whole, nutrient-dense options in your diet, you can reduce these risks and improve your long-term health. Prioritizing nutritious food choices is a crucial step towards a healthier life.

Frequently Asked Questions

Processed foods are simply altered from their natural state for preservation or convenience, like canned vegetables or pasteurized milk. Ultra-processed foods are industrial formulations with many added ingredients, such as flavorings, additives, and preservatives, and bear little resemblance to their original form.

Processed foods contribute to weight gain because they are typically very high in calories, added sugars, and unhealthy fats but low in fiber and protein. This combination makes them less satiating, often leading people to consume more calories than they would with whole foods.

Yes, consumption of processed foods is linked to chronic, low-grade inflammation in the body. This is often attributed to high intakes of sugar, unhealthy fats, and various food additives that can alter the gut microbiome and trigger immune responses.

Instead of sugary cereal, try rolled oats; instead of bagged chips, opt for nuts or homemade popcorn; and swap sodas for infused water. Cooking meals at home with fresh, whole ingredients is one of the best ways to reduce your intake.

Processed foods can negatively affect gut health by disrupting the microbiome, promoting the growth of harmful bacteria, and reducing microbial diversity. Additives can also increase intestinal permeability, contributing to what is sometimes called 'leaky gut'.

No, not all processed foods are unhealthy. Minimally processed foods like frozen vegetables, plain yogurt, and canned beans retain most of their nutritional value. The main health risks are associated with highly or ultra-processed foods, which are often high in added sugar, fat, and sodium.

Yes, research shows a link between high consumption of ultra-processed foods and a higher risk of mental health issues such as anxiety, depression, and cognitive decline. This may be due to the effects of inflammation and imbalances in the gut-brain axis.