4 Surprising Ways Being Obese Could Weaken the Immune System

coronavirus, fat, obesity weakens immune system

4 Surprising Ways Obesity Could Weaken Immune System

Obesity increases the chances of developing severe issues that affect nearly every organ and tissue of the body. These include the heart, brain, blood vessels, liver, gallbladder, and bones.

Excess body fat increases the risk of type 2 diabetes, hypertension, cardiovascular diseases, and premature death.

According to scientists, obesity (body mass index [BMI] of 30-39) or being overweight (BMI of 25-29) can also weaken the body’s immune system. Several studies have linked obesity with a reduced ability to fight infections.

Here are some lesser-known ways obesity affects the immune system:

1. Weakens the Immune System

Obesity has been shown to impair immune responses in some studies. It affects the production of defensive blood cells or decreases their ability to fight off infections.

Furthermore, obesity could weaken the immune system by:

  • Dysregulation in the production of cytokines
  • Altering the function of monocytes and lymphocytes
  • Dysfunction in the Natural killer cell
  • Reducing the killing properties of macrophages and dendritic cells
  • Decreasing the response to antigen stimulation

The impairment of these immune cells could lead to a weaker immune response in people who are obese. They may also have a higher risk of developing metabolic diseases and infections.

ABCnews.com reported a 2008 study with mice subjects that revealed that the obese mice had a compromised immune response to infectious agents. Because of this, they were more susceptible to infection.

White blood cells (WBC) are part of the innate immune response that fights against foreign invaders entering the body. The WBCs of obese mice in the study had “lower levels of a signaling molecule.” In addition, genes that help reduce inflammation were affected.

So, these mice had less ability to combat infectious agents than other normal-weight mice. The researcher stated that the “same mechanism is at work in humans.”

Natural Killer Cells Overburdened with Fat Can’t Function at Optimal Level

A 2018 article from Technology Networks reported on a study published in Nature Immunology in which researchers discovered how obesity adversely affects specialized cells in the immune system.

Based on the evidence presented, the researchers concluded that when a body has significant amounts of excess fat, that fat can accumulate in Natural killer cells. These cells are necessary for fighting off viruses, including tumors.

The study also reported that this accumulation in the Natural Killer cells can induce failure in the immune system signaling and “surveillance.” 

Natural killer cells “secrete” specific enzymes that can reduce or impede the growth of tumors; however, this function is reduced significantly or inhibited when the NK cell is overburdened with unhealthy fat.

Obesity is complex. It alters many processes and pathways – any of which could negatively affect the immune system.

2. Could Increase Susceptibility to Infections

According to available data, obese individuals are more likely than their normal-weight counterparts to develop severe infections of various types and develop complications.

These infections include:

  • Respiratory infections – Influenza, cold, pneumonia, and SARS (e.g., Coronavirus)
  • Urinary tract infections
  • Pancreatitis
  • Skin infections and cellulitis
  • Viral hepatitis

The correlations between being overweight, obesity, and infections have recently received more recognition due to emerging data indicating a strong association between obesity and poor prognosis in the COVID-19/coronavirus pandemic. 

Overweight and obese individuals may be more prone to infectious agents such as viruses, bacteria, and pathogens. They may also have delayed responses to vaccines.

According to numerous published studies (e.g., study1 study2 study3), there are three levels in which obese people’s immune system responses are potentially in a more weakened state than the non-obese.

Those three levels include the first line of defense (innate immune system), the second line of defense (adaptive immune response), and the third line of defense which involves the creation of memory cells that remember pathogens should they enter the body again.

Obese individuals may also face more difficulty in clearing the infection and in healing wounds.

Several articles, including one from USA Today (April 2020), reported that the obese and individuals with high blood pressure were the most hospitalized cases of the coronavirus.

More research keeps surfacing as to why these two groups are the most vulnerable to fatally succumbing to the coronavirus (not far behind are individuals with chronic lung disease, diabetes, and cardiovascular disease).

One reason overweight and obese individuals may be more at risk of hospitalization with complications from coronavirus is that obesity lowers the immune system response. It occurs because it increases chronic-low grade inflammation in the body. 

Temporary Inflammation is Necessary; Chronic Inflammation is Dangerous

Temporary inflammation fights off viral infections, bad bacteria, pathogens, etc. However, when the inflammation becomes more permanent, problems occur.

Researchers have characterized obesity as a state of low-grade chronic inflammation. Fat cells permanently switch on the immune response and keep the body always in a state of inflammation.

Chronic low-grade inflammation is considered a precursor to many other health conditions like heart disease, high cholesterol, and atherosclerosis.

Additionally, obesity increases a person’s chances of developing high blood pressure and type 2 diabetes.

According to researchers, people with diabetes usually have higher levels of a receptor called ACE2, which the coronavirus binds to and then enters a cell. This receptor tends to be in specific organs like the kidneys, lungs, heart, and small and large intestines.

However, research is showing that a large concentration of it may exist in nose cells. The theory is that the receptors in nose cells may play a significant part in how the coronavirus enters the body. 

Additionally, according to an October 2020 article in the journal Nature, researchers discovered:

And adipose tissue expresses relatively high levels of the ACE2 (angiotensin-converting enzyme 2) receptor that SARS-CoV-2 uses to gain entry into cells. “Adipose tissue seems to work like a reservoir of the virus,” says Gianluca Iacobellis, an endocrinologist at the University of Miami in Florida.

Initial research also revealed that Cov-19 appeared to “linger for about five days longer in people who are obese than in those who are lean.”

Obesity may increase the risk for nosocomial infections, periodontitis, surgical-site infections, and skin infections.

3. Could Lower the Effectiveness of Vaccines

Some studies have suggested relationships between obesity and vaccine response. Researchers have investigated obesity and hepatitis B vaccines. Their studies show strong evidence that obese people may have a very high non-response rate to hepatitis B vaccination.

It means the immune system of people with obesity did not produce the disease-fighting antibodies to the extent needed to protect against the invading pathogens.

Evidence shows that obese people may be more likely to respond poorly to the flu vaccine. During the 2009 flu pandemic, doctors and scientists noticed that obese people were having a rougher time dealing with the virus than non-obese. 

Research from a study at the University of Maryland also noted that for some reason, the virus was able to spread and lodge itself more deeply into the lungs of their significantly overweight participants. Because of this, they were exhaling more of the virus. Researchers concluded this could potentially escalate an outbreak.

4. Could Increase the Risk of Autoimmune Diseases and Other Conditions

The immune system maintains a balance between giving its own body’s cells a free pass and attacking external threats such as infection-causing pathogens. 

However, in obese people, the balance is turned upside down – i.e., the body’s immune system starts killing its cells and tissues. This reaction may offer one explanation for why obese people are at a higher risk of developing autoimmune disorders, type 2 diabetes, rheumatoid arthritis, and certain cancers.

Several studies have also implicated obesity as a possible risk factor for multiple sclerosis and Crohn’s disease.

Research shows that obesity adversely affects every part of the body, including the immune system response. 

The more body fat a person has, generally, the more at risk they are of a weakened immune system response. A weakened immune response includes a decreased sensitivity to vaccines. 

Excess body fat puts a person at risk of slower healing wounds, increased risk of complications from infections, and autoimmune diseases.

Final Thoughts

Dropping just 5 to 10 percent of excess body weight can have a significant impact on overall health. It may also improve the immune system response. 


Lowering the risk factors includes addressing physiological issues and modifying diet and lifestyle. 


Working with a doctor can help address potential physiological issues that could be preventing weight loss.

If you found this article helpful, would you mind sharing it? We’d greatly appreciate it!



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