Inflammation is part of your body's natural defense against things that adversely affect health, like bacteria, viruses and toxins.

But your immune system is complicated, and its components are sometimes triggered by unexpected things — including certain foods.

"Our diets play an enormous role in what's happening inside our bodies, much more than most people probably realize," says Dr. Karla Saint Andre, an endocrinologist at Houston Methodist.

We all know the obvious consequence of making consistently unhealthy food choices: weight gain. What you may not realize is that being overweight is linked to increased levels of inflammation in the body.

The story of how our eating habits can lead to inflammation doesn't stop there.

"An unbalanced diet means eating a lot of processed foods, which contain ingredients that can activate inflammatory processes directly," Dr. Saint Andre adds.

This is less noticeable than weight gain, of course, but Dr. Saint Andre emphasizes that it's still harmful.

What foods cause inflammation?

There's more bad news: The problem foods are ones that happen to be abundant throughout the typical American diet.

The five types of foods that cause inflammation include:

1. Red meat and processed meats, including bacon, hot dogs, lunch meats and cured meats
2. Refined grains, including white bread, white rice, pasta and breakfast cereals
3. Snack foods, including chips, cookies, crackers and pastries
4. Sodas and other sweetened drinks
5. Fried foods
   
   

What these foods all have in common is that they contain added sugars, saturated fats and/or trans fats. With the exception of red meat, these are also all considered processed foods.

Alcohol can also cause inflammation.

What's more, alcohol is often combined with the aforementioned inflammation-promoting foods. When combined with refined grains, added sugars or mixed with soda, alcoholic drinks become a double whammy.

Why do these foods cause inflammation?

"The cells in your body absorb and react to processed foods differently than they do to natural foods," says Dr. Saint Andre.

Your body is programmed to metabolize and use the nutrients, vitamins and minerals that vegetables, fruits and whole grains provide. It requires these things, in fact, because they help coordinate essential functions necessary for existence.

The refined forms of sugars, fats and grains that are packed into processed foods are a different story. They're not needed. Plus, your body doesn't always know what to do with them — especially when they're consumed in large amounts.

"Foods that have high levels of fat, sugar and other refined carbohydrates are essentially toxic to our bodies and trigger inflammatory pathways through a number of direct and indirect ways," warns Dr. Saint Andre.

For instance, refined vegetables oils added to processed foods can throw your omega-6 to omega-3 fat ratio out of whack. Although not a source of refined fat, red meat can, too, since it contains high levels of omega 6 fats.

Omega-6 and omega-3 are essential fatty acids that the body cannot produce but are necessary to survive. Although foods with higher omega-6 fatty acid content are generally healthy, higher intake in proportion to omega-3 fatty acids leads to an overall increase of inflammatory diseases.

Experts consider the ideal omega-6 to omega-3 fatty acid ratio to be around 2:1, helpful in the prevention of cardiovascular disease and cancer; a 5:1 ratio has shown benefit in preventing some diseases as well, compared to the 10:1 ratio seen in the typical American diet. Dr. Saint Andre recommends increasing your consumption of omega-3s and avoiding excess consumption of omega-6s.

"This omega-6/omega-3 imbalance activates proinflammatory substances called cytokines, which contribute to fatty buildup in the arteries that leads to a chronic inflammatory state (atherosclerosis) and what's called oxidative stress," explains Dr. Saint Andre.

(More on oxidative stress in just a bit.)

Then there's how added sugar and refined grains — both plentiful in many processed foods — cause spikes in your blood sugar.

"Having elevated blood sugar levels activates proinflammatory pathways," says Dr. Saint Andre. "Additionally, continued blood sugar spikes can eventually lead to insulin resistance and diabetes, which are also linked to inflammation."

Lastly, a diet that prioritizes processed foods over natural ones is inherently unbalanced and hypercaloric, leading to weight gain.

"As our weight increases, the amount of fat cells also increases," explains Dr. Saint Andre. "These cells secrete many hormones and substances, some of which put the body into an inflammatory state."

The bottom line: These foods can directly activate pro-inflammatory substances and indirectly promote weight gain, all of which lead to inflammation in the body.

But ... how bad is all of this, really?

Most people don't notice the subtle signs of eating inflammation-promoting foods.

But this underlying, persistent inflammation eventually leads to symptoms ranging from annoying to somewhat debilitating, including:

• Chronic fatigue
• Frequent or recurrent infections
• Joint and muscle pain
• Insomnia
• Gastrointestinal diseases, such as acid reflux, constipation and diarrhea
• Anxiety and depression
  
  

"The other issue with being in a pro-inflammatory state is that it leads to oxidative stress, when toxic waste products that are usually kept in check by our body are allowed to accumulate and cause harm," explains Dr. Saint Andre.

And it's a vicious cycle since this oxidative stress can cause more inflammation as well.

Left unchecked, the damage caused by inflammation and oxidative stress can lead to serious health conditions, including:

• High blood pressure
• Diabetes
• Heart disease
• Cancers
• Liver disease
• Kidney disease
  
  

This explains why nutritionists and doctors encourage eating foods rich in antioxidants, which counter oxidative stress and constitute a cornerstone of an anti-inflammatory diet.

How to adjust your diet to reduce inflammation

"The most important thing is to limit inflammation-promoting foods — the sodas, refined carbohydrates, processed and packaged foods," says Dr. Saint Andre.

Ideally, she adds that we should instead eat a diet mainly composed of healthier, natural sources of carbohydrates and fats that also contain the protein and fiber we need, including fruits, vegetables, whole grains, legumes and nuts, lots of fatty fish and olive oil.

"These are foods that lead to the stabilization of insulin and a well-balanced omega-3 to omega-6 fat ratio, reducing the risk of inflammation," explains Dr. Saint Andre. "And, when consumed in proper portions, they're also not likely to contribute to weight gain."