Does a Fast Food Diet Cause Inflammation?

fast food and inflammation

“Fast food isn’t good for you!” How many times have you heard that mantra? But the convenience of pulling into a drive-thru window and grabbing a bag of hot food is too much to resist. Are you trading convenience for health? Eating a fast food diet is linked, in some studies, with a higher risk of cardiovascular disease, stroke, type 2 diabetes, and obesity. Despite the health downsides of eating fast food, many people, particularly young people, continue to eat it. Statistics from the Bureau of Labor shows that millennials spend almost half of their food budget on restaurant food, including fast food.

Why is fast food so harmful to your health? For one, it’s highly processed and made with cheap, industrial oils. The lack of fiber and copious amounts of added sugar make it hard on your blood glucose and body weight. Research also shows that people consume more calories when they eat at a fast food restaurant. What’s more, there’s evidence that fast food can trigger inflammation. If that’s the case, it may partially explain some of its health risks since inflammation is the driving force behind most health problems, even cardiovascular disease.

Fast Food and Inflammation

The first evidence that fast food is pro-inflammatory comes from mice. A study published in the journal Cell found mice that were bred to be predisposed to cardiovascular disease developed a whole-body inflammatory response when they ate the mouse equivalent of a typical Western diet. Once they switched to a healthier diet, the inflammation subsided. What’s more, the mice, after eating the equivalent of fast food, developed harmful changes to precursor cells that make white blood cells, the cells that fight off infection. These changes didn’t reverse even after they switched to a healthier diet. When the mice were exposed again to circumstances that incited inflammation, their white blood cells overreacted as if they remembered the previous insult. In response, it set off a cascade of tissue-damaging inflammation. It’s as if the fast food primed the white blood cell precursors to be on higher alert and respond to any sign of danger with an aggressive, inflammatory response.

Does the Same Happen in Humans?

You can’t always draw conclusions about humans from mouse studies. Does the same happen in humans? It looks that way. In one Australian study, researchers found eating a single fast food meal high in saturated fat was linked with an increase in airway inflammation in asthmatics. So, potentially, eating fast food can worsen the symptoms of asthma.

In another study, researchers asked 9 people to eat a 900-calorie fast food meal high in saturated fat and carbs. After the meal, they took blood samples from the participants every hour for 3 hours. The researchers found that the number of free radicals, markers of oxidative stress, spiked after the unhealthy meal and lasted for at least three hours. Your body sees fast food as a foreign invader and treats it similar to an infection-causing agent like a virus or bacteria! Interestingly, there’s some evidence that consuming antioxidants along with fast food may reduce the inflammatory response. So, at least, eat some vegetables with that fast food!

Fast Food is Bad for Your Blood Vessels Too

As if generalized inflammation isn’t bad enough, research shows that fast food is harmful to your blood vessels too. In one study of 24 subjects, subjects ate various McDonald’s fast food meals before the researchers used a special study to determine how their arteries responded to the meals. The three meals they ate were:

Meal one:   Beef burger with French fries, ketchup, lemon-flavored soda
Meal two:    Vegetarian burger, French fries, ketchup, lemon-flavored soda
Meal three:   Vegetarian burger, salad, yogurt, fruit, orange juice

Healthy arteries have good “endothelial function, referring to the thin, one-layer of cells that surround the inner walls of arteries. This layer of cells is called the endothelium and is important for heart and blood vessel health. When the endothelium is healthy, it secretes substances that cause the artery it lines to dilate. When arteries dilate in a healthy manner, they can carry more oxygenated blood to tissues and blood pressure is better controlled. Plus, the endothelium plays a key role in blood clotting. An unhealthy endothelium is a precursor to cardiovascular disease.

In the study, researchers used flow-mediated dilation to measure endothelial function 2 hours after each fast food meal. Interestingly, all three meals were associated with a reduction in endothelial function and the way the blood vessels behave. The fact that meal three with vegetables and fruits didn’t improve endothelial function suggests that adding antioxidant-rich components to the meal didn’t prevent the decline in endothelial function. All three meals had the same negative impact on endothelial function.

Interestingly, all three meals are relatively high in sugar due to the beverages, so the sugar content may have been a factor in the poor endothelial activity. A study published in the American Journal of Clinical Nutrition found that endothelial function deteriorates after consumption of glucose.

What about Blood Pressure?

Eating a fast food meal may have an immediate, negative impact on your blood pressure. In one study, 30 healthy participants ate either a high-fat, fast food meal with 42 grams of fat. The other half ate a low-fat, fast food meal with 1.3 grams of fat. The participants were then challenged with a series of stressful tests designed to increase their blood pressure. A week after, the groups switched and ate the opposite meal. The study showed that the higher fat fast food meal led to a greater rise in blood pressure than the lower fat fast food meal. These days, there’s less focus on saturated fat as a risk factor for cardiovascular disease, but it’s wise not to overdo the saturated fat, especially if it comes from a fast food restaurant.

The Bottom Line

Now, you have more reasons to limit the amount of fast food you eat! Plan your meals ahead of time so you can avoid an untimely trip to the golden arches. Your heart and blood vessels will thank you!



HealthLine.com. “The Effects of Fast Food on the Body”
Examine.com. “Does fast food make the immune system more aggressive in the long term?”
Cell. 2018 Jan 11;172(1-2):162-175.e14. doi: 10.1016/j.cell.2017.12.013.
American Journal of Respiratory and Critical Care Medicine 2017;195: A7467.
Science Daily. “Eating High-Fat Meal Raises Blood’s Proinflammatory Factors; Vitamins E, C Counter Response”
Nutr J. 2014; 13: 61. Published online 2014 Jun 17. doi: 10.1186/1475-2891-13-61.
Physiol Rep. 2018 Sep; 6(18): e13867. Published online 2018 Sep 17. doi: 10.14814/phy2.13867.
Am J Clin Nutr. 2007 Aug;86(2):334-40.
The American Journal of Cardiology 79(3):350-4 · February 1997.
Am J Clin Nutr. 2008 Jul; 88(1): 51–57.doi: 10.1093/ajcn/88.1.51


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