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How Are Chronic Inflammation and Obesity Connected?

7 min read

Chronic inflammation has got increased attention by the scientific community, and rightly so. I’d like to discuss how it is related to obesity and why we should do more to cut our levels of chronic inflammation.

The main points are summarized at the end of the post, as always.

There’s still a lot of people who are unfamiliar with inflammation, however, it is being increasingly recognized as one of the major players in a huge number of diseases. First, I’ll briefly describe the general, short-term inflammation response. Afterwards, I’ll move to the main topic of chronic inflammation and obesity.


What is inflammation?

Inflammation by itself is a natural defensive response of our body to different harmful stimuli. This response involves some key players which include which host cells, blood vessels, and proteins. It’s characterized as an adaptive immune response to tissue injury or infection. The most common signs of inflammation are heat, redness, swelling, and pain on the place of your body where the inflammatory process has begun.

The main “goal” of inflammation is to:

  • Eliminate the first cause of cell injury; this prevents the “hostile” substances from spreading throughout the body
  • Remove damaged tissue and pathogens
  • Initiate the process of repair

In order to meet these goals, the body must activate and bring white blood cells and plasma proteins, which are always present in our body, to the site where an infection has occurred. The process is initiated by two types of white blood cells (macrophages and mastocytes) and by dendritic cells (among others). These compounds have certain receptors which recognize molecules that are shared by pathogens, but can separate them from our own cells. Through this they can clean up and help the body recover by destroying the harmful substances and at the same time avoid doing harm to our own tissue.

However, this process can be potentially harmful as well. Certain components of the inflammation response are capable of destroying our own healthy tissue where the response is initiated. Moreover, an inappropriate inflammatory response when there are no foreign (dangerous) substances to fight off leads to autoimmunity.

Autoimmunity is the failure of an organism in recognizing its own parts. This leads to an immune response against our own cells and tissues, such responses are called autoimmune diseases.

That is why the inflammatory process is closely regulated by your immune system. This avoids excessive, healthy tissue damage.

And that was the main gist of the short-term inflammatory response. While we can see that it is generally a helpful thing for our body, the long-term (chronic) response is where the problems start arising.


What about chronic inflammation?

Out of the ten leading causes of mortality in the United States, chronic, low-level inflammation contributes to the pathogenesis of at least seven. These include heart disease, cancer chronic lower respiratory disease, stroke, Alzheimer’s disease, diabetes and nephritis. Center for disease control and prevention, 2011

Chronic inflammation can be triggered by a lot of different events, these include cells that no longer work optimally and cellular stress. Either of these can be caused by:

  • Increased caloric consumption
  • Constantly blood sugar levels
  • Oxidative stress

The issue with chronic inflammation many people are not aware of is that we don’t necessarily notice it while it’s going on. And it can go on for many years, even decades, if we live unhealthy lifestyles. Chronic inflammation increases the amount of cells dying in our body (apoptosis), and with that it has important implications for the normal functioning of your body. If we dive into the mechanisms, there are a few ways how chronic inflammation leads to negative consequences:

1. Mitochondrial dysfunction

If you remember your high school biology classes, you will remember that mitochondria are lovingly called the “power plants” of our bodies. This is where cells produce the needed energy (ATP). Mitochondrial dysfunction is a consequence of chronic inflammation caused by outside stressors such as tobacco smoke or different toxins, or by inside stressors such as an increased amount of reactive oxygen species (ROS). Through a cascade of events this can lead to cell death or uncontrolled cell growth, more commonly known as cancer.

2. Advanced glycation end products

When fructose and glucose come into contact with proteins and lipids (fat cells), they create advanced glycation end-products (AGE). Elevated blood sugar levels can increase AGE levels themselves. They can be also found in foods cooked at higher temperatures, especially red meat. They tend to make arteries stiff, oxidize LDL particles, increase oxidative stress, and others.

3. Oxidized lipoproteins

Chronic inflammation makes our LDL particles (commonly called “bad cholesterol”) more prone to oxidation. And oxidized LDL particles are the major contributor to atherosclerosis, and not cholesterol in general.

There is also uric acid and homocysteine which are involved in chronic inflammation as well.

And with that out of the way, let’s turn our attention to obesity now.


How does all of this relate to obesity?

Your belly fat is not just belly fat. It has been long recognized as an endocrine organ. That means it stores and secretes different hormones and thereby affects your metabolism as well. One particular effect involves the secretion of two molecules (cytokines are one that will appear throughout this segment) which induce a strong inflammatory response. [12 ]

Furthermore, macrophages infiltrate your fatty tissue and secrete another set of molecules which further help inflammation. And this accumulation of macrophages is thought to be one of the major causes of chronic inflammation and insulin resistance in obese people. [3, 4]

Furthermore, diets which are high in saturated fat and trans fats are associated with higher levels of some of the molecules which induce inflammation, this becomes especially pronounced in people who are either diabetic or overweight [5]. This connection is also more clear in diets with high amounts of trans fats than it is with saturated fats [67].

Eating too much in general is one of the biggest contributors to chronic inflammation, this is also one of the reasons why caloric restriction or intermittent fasting is healthy for us.

“You didn’t convince me yet, chronic inflammation is no big deal”

Chronic inflammation is an essential part of atherosclerosis, and it is being debated whether it is the main reason behind heart disease. Increased levels of cytokines, which promote inflammation, are predictors of heart failure, stroke, coronary heart disease, and peripheral arterial disease. [8]

Moreover, the following types of cancer are all characterized by the presence of chronic inflammation:

  • Lymphoma
  • Prostate
  • Ovarian
  • Pancreatic
  • Colo-rectal
  • Lung cancer

Increases in cytokines are only one of a multitude of mechanisms through which chronic inflammation contributes to the progression of this disease [910]. The mentioned cytokines decrease your insulin sensitivity and are also present in greater numbers in people with type two diabetes. [11, 12]

Several observational studies note that chronic inflammation is connected to cognitive decline and dementia; including vascular dementia and Alzheimer’s disease, in older people [13]. One particular study found that people with the lowest levels of C-reactive protein, an inflammatory marker, had a 30-40% reduced risk for cognitive decline when they were compared to a group with the highest CRP levels [13]. There is even some recent evidence suggesting that chronic inflammation has a strong connection to depression. The exact nature of this relationship is unknown as of yet. [14]

And finally, obesity by itself is considered to be a major cause of chronic inflammation [15]. This is just another reason for getting rid of excess weight is important for increased health, since the increases in inflammatory cytokines are reversible with fat loss. [16]


Take home messages

  • Chronic inflammation and obesity are connected through different hormones. While short-term inflammation is a good and healthy response of our body to help with dangerous tissue, long-term inflammation is connected and can cause a number of diseases.
  • Chronic inflammation has been connected to depression, cognitive decline, and various types of cancer (pancreatic, colorectal, lung ovarian, prostate, and lymphoma)
  • Chronic inflammation is an essential part of atherosclerosis
  • Obesity can cause long-term inflammation, other causes include prolonged stress, smoking, and other different long-term stressors

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