Fast food puts the immune system into overdrive. In a University of Bonn study, mice ate a high-fat, high-sugar, low-fiber fast-food diet. They developed body-wide inflammation. Their immune programming stayed switched on even after they went back to a healthy diet.
Bad habits are easy to pick up but very hard to drop. This could be anything, such as binge eating, drinking too much booze, sleeping too much or too little, and eating too much junk food. It is now emerging that fast food will not just make you overweight and obese. It also can damage your immune system.
Does fast food cause inflammation?
A recent study by the University of Bonn linked fast food with an immune system in overdrive, which leads to inflammation. The study also tied that inflammation to chronic conditions such as heart and blood vessel diseases and type 2 diabetes. The study concluded that fast food makes the immune system more aggressive in the long term. Even after a change to a healthy diet, the body’s defenses stay overactive.
Details of the Study
This was a lab study. The researchers put mice on a fast-food diet for a month. The diet was high in fat, high in sugar, and low in fiber. The animals developed a strong inflammatory response throughout the body. It was much like what happens after an infection. The mice also had more of certain immune cells called granulocytes and monocytes. This was a sign that progenitor cells (the parent cells) in the bone marrow were involved.
Then the researchers gave the mice their usual cereal diet for the next month, and the inflammation died down. But they saw that something key did not change: the programming of the progenitor cells. The genes that had been switched on during the fast food phase were still active. They could still trigger inflammation. The innate immune system has a memory which “records” such changes and stores them. This may also explain why overweight children are more likely to become obese adults than slimmer children are.
What are the long-term effects of eating fast food?
The wrong food can cause severe long term harm. Once you get hooked on fast food, your immune system is set on overdrive. This is likely to start a process of acute, then chronic inflammation. Even after you switch to healthier meals, your immune system may not be able to reset. So you will still be prone to an immune system overdrive and at risk for chronic inflammation. Chronic inflammation has been linked to heart disease and stroke as well as autoimmune diseases. Researchers are also now trying to establish the link between chronic inflammation and cancer.
Fast food is also well known to be linked to obesity and food addiction. The high fat and high salt content may be responsible for its addictive pull. One review published in NCBI suggested that fast food causes mental dependence and obesity over time. The study noted that most fast food usually comes with soda, which raises the sugar content 10-fold. Fast food is high in calories but low in fiber and nutrition. Outside factors such as packaging, pricing, convenience, and ads also play a role.
How do you stop eating fast food? 10 tips for healthy eating habits
- Make mealtimes fun for the kids. You can do this by having them help plan the menu and make the food. Teach kids the nutrients each meal gives them. Let them plan their own meals based on nutrition. Make sure the food always looks tempting and the portions fit their age.
- Skip refined grains, such as the breads, cereals, and grain snacks kids are used to. Gluten and gliadin in grains drive leaky gut and autoimmune problems. Fill the plate with vegetables, fruit, eggs, meat, and fish instead. It may take some time before the kids get used to this but in the end, it will be worth every effort.
- Cook with real olive oil or butter. Skip seed oils such as canola, corn, safflower, sesame and sunflower oil. They are harmful, not healthy fats.
- When choosing protein sources, go for red meat, chicken, fish, and beans. Remove the skin of the chicken before preparing to make it healthier. Red meat and fish are good for you, so there is no need to limit red meat to once a week.
- When you buy packaged foods, read the labels carefully. Pick the ones rich in fiber, minerals, and vitamins. Limit those with sodium, added sugars, saturated fat, and trans fat.
- Eat at home as often as you can. This gives you more control over the ingredients, portion sizes and servings.
- Keep fresh fruits and vegetables in plain sight in the kitchen and living rooms. That way family members can see them and reach them. It is easy for a family to pick up healthy eating habits when they don’t have to go out of their way to find healthy food.
- Add oily fish to your diet. This includes fish such as salmon, mackerel, anchovies, and trout, which are high in omega 3 oils.
- Find healthy ways to cook meals, such as steaming, baking, and grilling instead of frying. Do not add extra oil, salt, or sugars to your recipes to make them more tempting.
- Talk with a nutritionist or dietitian when you need help. Starting and sticking with a healthy eating plan for your family is not easy. But with the right support, you are sure to succeed.
Frequently asked questions
How does fast food affect your immune system?
Fast food pushes the immune system into overdrive. In a University of Bonn study, mice ate a high-fat, high-sugar, low-fiber fast-food diet for a month. They developed a strong inflammatory response throughout the body, much like the response to an infection. Their granulocytes and monocytes increased. That was a sign that progenitor cells in the bone marrow had been drawn in.
Does the immune system go back to normal after you stop eating fast food?
Not completely. The mice in the Bonn study went back to their usual cereal diet for a month. The inflammation died down, but the programming of their bone-marrow progenitor cells did not. Genes switched on during the fast-food phase stayed active and able to trigger inflammation again. The innate immune system keeps a memory of that diet.
Why is fast food so addictive?
The high fat and high salt content may be responsible for fast food’s addictive pull. Most fast-food meals also come with soda, which raises the sugar content tenfold. Beyond the food itself, packaging, pricing, convenience and advertising keep people coming back. Over time the result is psychological dependence and obesity.
What diseases are linked to chronic inflammation?
Chronic inflammation has been linked to heart disease, stroke and autoimmune diseases. Researchers are working to establish its link to cancer. The Bonn study also tied fast-food inflammation to heart and blood vessel disease and type 2 diabetes. That is the danger of a diet that keeps the immune system on alert. Acute inflammation turns chronic, and chronic inflammation feeds these conditions.
Related reading
References
- NCBI (2011): Is fast food addictive? Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/21999689
- Cell (2017): Western Diet Triggers NLRP3-Dependent Innate Immune Reprogramming. Retrieved from https://www.cell.com/cell/fulltext/S0092-8674(17)31493-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0092867417314939%3Fshowall%3Dtrue
- Live Science (2018): What Is Inflammation? Retrieved from https://www.livescience.com/52344-inflammation.html
Medically reviewed by Dr. Gurpreet Singh Padda, MD, MBA, MHP
Interventional pain physician, addiction medicine specialist and obesity medicine diplomate.
Licensed in Missouri and Illinois.
Last reviewed June 18, 2026
