Mar 152020

4 Surprising Ways Being Obese Weakens the Immune System

4 Surprising Ways Being Obese Weakens the Immune System

4 Surprising Ways Obesity Weakens Immune System

Obese people have higher 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. Obesity 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 and clinical trials 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 weakens 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 leads to a weaker immune response in people who are obese. They have a higher risk of developing metabolic diseases and infections.

Results from a 2008 study in animal subjects revealed that the obese animals had compromised immune response to infectious agents. Because of this, they were more susceptible to infection. White blood cells are part of the innate immune response that fights against foreign invaders entering the body. The WBCs of obese animals in the study, however, had “lower levels of a signaling molecule” and altered genes that reduce inflammation. So, these animals have less ability to combat infectious agents than other normal-weight animals. The researcher stated that the “same mechanism is at work in humans.”

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

A 2018 article from Technology Networks reported on a study published in Nature Immunology in which researchers discovered how obesity adversely affects certain 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 important 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 significantly reduced or inhibited when the NK cell is overburdened with fat.

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

2. Prone to Infections

According to available data, obese people are more likely than normal-weight people to develop severe infections of various types and develop serious complications of common infections, including:

  • 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 heightened 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 fungi, and have delayed responses to vaccines.

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

Several articles, including one in the April 2020 edition of USA Today, stated that the obese, as well as 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 why significantly overweight and obese individuals may be more at risk of hospitalization with complications from coronavirus is that obesity lowers the immune system response. This occurs because it increases chronic-low grade inflammation in the body.

Temporary Inflammation is Necessary; Chronic Inflammation is Dangerous

Temporary inflammation is needed to fight off viral infections, bad bacteria, pathogens, etc.; however, when the inflammation becomes more permanent that is when it becomes a problem and even dangerous. 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 an important 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, we know now that 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 certain organs of the body like the kidneys, lungs, heart, and the 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.  

Besides that, obesity is an established risk factor for nosocomial infections, periodontitis, surgical-site infections, and skin infections.

3. Lowers the Effectiveness of Vaccines

Some studies have suggested relationships between obesity and vaccine response. A lot of research work and clinical trials have been done regarding obesity and hepatitis B vaccines. These studies show strong evidence that obese people have a very high non-response rate to hepatitis B vaccination. This means the immune system of people with obesity was not able to produce the disease-fighting antibodies to the extent needed to protect against the invading pathogens.

When it comes to the flu vaccine, evidence shows that obese people are more likely to respond poorly to the vaccine. During the 2009 flu pandemic, doctors and scientists noticed that obese people were having a harder time dealing with the virus than the 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, and because of this, they were exhaling more of the virus. Researchers concluded this could potentially escalate an outbreak.

4. Increases the Risk of Autoimmune Diseases

The immune system is designed to maintain 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 own cells and tissues.

This is the reason why obese people are generally at a higher risk of developing autoimmune disorders such as type 2 diabetes, rheumatoid arthritis, and certain cancers. Several studies have also implicated obesity as a possible risk factor for the development of multiple sclerosis and Crohn’s disease.

It’s been well documented 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 the weakened immune system response. The 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 the current 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 be helpful in addressing potential physiological issues that could be preventing weight loss. 


Coronavirus, diabetes, obesity and other underlying conditions: Which patients are most at risk?;

Obesity Weakens Immune Response;

8 Weird Ways Obesity Makes You Sick;

Excess Weight Can Weaken The Flu Shot;

Nearly All Patients Hospitalized With Covid-19 Had Chronic Health Issues, Study Finds;

High blood pressure linked to increased risk of dying from COVID-19;

Obesity, inflammation and the immune system;

The impact of obesity on the immune response to infection;

The impact of obesity on the immune response to infection.;

Obesity could increase the severity of flu;

Excess Weight Can Weaken The Flu Shot;

‘Fat-clogged’ Immune Cells Fail to Fight Tumors;