Obesity Impacts Flu Transmission

Analysis by Dr. Joseph Mercola

flu transmission

Story at-a-glance -

  • Nearly 40 percent of the U.S. population are obese, increasing their risk for diabetes, stroke, cardiovascular disease and complications related to infections, including hospitalization and death
  • Data shows those who are obese transmit the flu virus longer than those who are not
  • Obesity is also connected to the risk of certain cancers, which I believe you may virtually eliminate by adhering to strategies to help normalize your weight and insulin/leptin sensitivity
  • Your immune system is complex, affected by a number of different bodily systems; I share strategies to support your immune system including your gut microbiome, lymphatic system, sleep and grief

Nearly 40 percent of the U.S. population are obese1 and, worldwide, those who are obese outnumber people who are underweight from starvation by a significant margin.2 The CDC estimates 20 percent of children ages 6 to 19 are also obese,3 and rates of diabetes, associated with being overweight, nearly doubled in 20 years, from 5.5 percent in 1994 to 9.4 percent in 2015.4

In a 2014 report, obesity was linked to an estimated 500,000 cancer cases worldwide each year.5 More recent statistics from the U.S. Centers for Disease Control and Prevention (CDC) show the reality is far grimmer, at least in the U.S.6 Obesity-related conditions also include heart disease, stroke, high blood pressure, gout and sleeping problems.7

Data from humans and animal model research have demonstrated obesity impairs your immune response or function leading to an increased risk for a variety of infections.8 While the effect is demonstrable, the cause has not been defined. Recent research also finds obesity affects transmission of the flu virus.9

Obesity Affects Transmission of Flu Virus

According to research, obesity may be a disease transmission vector. In other words, data finds those who are obese transmit the flu virus for a longer period of time than those who are not.10 Aubree Gordon, Ph.D., senior author from the University of Michigan School of Public Health, said:11

"This is the first real evidence that obesity might impact more than just disease severity. It might directly impact transmission as well."

Obesity increases your risk of suffering severe complications from the flu, including hospitalization and death.12 Findings from this recent study suggest obese adults infected with the flu virus transmit the virus to others for a longer period of time, which increases the opportunity for spreading the flu to others.

The researchers analyzed data from approximately 1,800 people in 320 homes in Managua, Nicaragua.13 The study took place over three flu seasons from 2015 to 2017, and evaluated adults with laboratory-confirmed influenza A virus. The data found those who were obese shed the virus 42 percent longer than those who were not obese.

Interestingly, obese individuals who experienced mild illness or had no symptoms shed the virus 104 percent longer than nonobese adults with the flu. Viral shedding was determined through nose and throat samples detecting the presence of influenza A, but not whether the virus was currently infectious.14

Additional research is underway to analyze whether the virus shed over longer periods is also infectious. While these findings suggest obesity may play an important role in the transmission of influenza A,15 no evidence was found to suggest it also increases transmission of influenza B, which typically triggers less serious disease.

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Obesity and Metabolic Syndrome Affect Your Immune System

While the exact cause of how obesity affects the immune system is unknown,16 an evidence-based association has been made. An individual who suffers from obesity but eats a relatively healthy diet and exercises is still at risk for an impaired immune function,17 which may be related to:18

  • Reduced cytokine production
  • Changed monocyte and lymphocyte function
  • Natural killer cell dysfunction
  • Decreased macrophage and dendritic cell function
  • Reduced response to antigen/mitogen stimulation

Metabolic disturbances may trigger chronic inflammation, tissue stress and dysfunction, and obesity increases your risk for chronic disease and clinical parameters associated with metabolic syndrome and insulin resistance.19 Research has also demonstrated the important role your immune system plays in the development of obesity.

Population studies have demonstrated similar results. For example, obese hospitalized patients have a higher risk for developing secondary infections and complications such as pneumonia, sepsis and wound infections.20

Another study from Boston University21 found obese individuals had a more difficult time fighting infections. Using an animal model infected with gum disease, the researchers discovered obese mice had a reduced ability to fight the gum infection than their normal weight counterparts.

The obese mice also had lower levels of important signaling molecules in the white cells and altered genes to fight inflammation. This supports previous studies22 demonstrating obesity may impair your body's ability to protect against bacterial or viral infections.

How Obesity Is Defined

Those who suffer from obesity have accumulated so much body fat it has a negative effect on their health. The amount of body fat you carry can be measured in several different ways. While the most commonly used measurement is the body mass index (BMI), BMI can be grossly misleading as it does not take muscle mass into account.

If your BMI is between 25 and 29.9, you are considered overweight and anything over 30 is considered obese.23 A far more accurate indicator of body composition is your waist size. With a tape measure, simply measure the distance around the smallest area of your abdomen, below your rib cage and above your belly button. The following is a general guide for healthy waist circumference:

  • Men — 37 to 40 inches is overweight; greater than 40 inches is obese
  • Women — 31.5 to 34.6 inches is overweight; greater than 34.6 inches is obese

Waist size provides a far more accurate benchmark for predicting your risk of death from a heart attack and from other causes than does BMI, and the reason for this is because your waist size is related to the type of fat that is stored around your waistline, called "visceral fat" or "belly fat."

This type of fat is strongly linked to Type 2 diabetes, heart disease, stroke and other chronic diseases. It is thought that visceral fat is related to the release of proteins and hormones that cause inflammation, which can in turn damage your arteries and affect how you metabolize sugars and fats.

An expanded waistline is associated with insulin resistance, high blood pressure, lipid imbalance, cardiovascular disease, thickening of the walls of your heart, and even increased risk for developing Alzheimer's disease decades later.

The Effect You Don't See

All of that said, the effects of being overweight are often invisible. When a woman is pregnant, for example, obesity may increase her risk of blood clots, gestational diabetes, preeclampsia and sleep apnea. If mom is obese, several complications may also arise before birth, including miscarriage, birth defects, macrosomia and premature birth. Other significant health risks associated with obesity include:24,25

Type 2 diabetes



Low quality of life

Kidney disease

Fatty liver disease

Gallbladder disease and gallstones

Heart disease and stroke

High blood pressure

Breathing problems such as sleep apnea and asthma

Body pain and difficulty with physical functioning

Increased risk death from all causes

Certain types of cancer (endometrial, breast, colon, kidney, gallbladder, esophageal, pancreatic and liver)

Pregnancy problems, such as high blood sugar during pregnancy, high blood pressure, and increased risk for cesarean delivery (C-section)

Mental illness such as clinical depression, anxiety and other mental disorders

Preventing Obesity Is Dependent on Your Lifestyle Choices

Fortunately, there is a lot you can do to lower your risk for obesity and manage your weight. Maintaining a healthy weight is part of a preventive lifestyle, but sometimes you need to achieve a healthy weight first.

I believe you can virtually eliminate your risk of cancer and chronic disease, and radically improve your chances of recovering if you currently have cancer, by adhering to strategies to help normalize your weight and insulin/leptin sensitivity. While the strategies are simple, making them effective and permanent may take time.

Behavior and environment are two factors playing a significant role in lifestyle choices.26 I recommend managing your stress as this contributes to disease and reduces your ability to make changes to your lifestyle. My favorite tool for resolving emotional challenges is the Emotional Freedom Techniques (EFT).

For more information about how obesity affects your health, and recommendations to reduce your risk for obesity-related cancers, see my previous article, "Obesity Now Causes Half a Million Cancers a Year, Worldwide."

Strengthen Your Immune System Naturally

Your immune system is complex and affected by a number of different systems in your body, not just your weight. So, whether you struggle with being overweight or not, there a number of strategies you may consider to strengthen your immune function.

Some may also help you achieve weight loss or better weight management, as much of your immune system and metabolism is tied to your gut microbiome. Here are several suggestions with links to my previous articles to help you get started.

Optimize your gut microbiome — While microbiome science is still in the early stages, scientists have explored why certain foods are good for us and others aren't. The connection between food, microbes and health are all inextricably intertwined, and unraveling the mysteries may shed light on how they affect our metabolism.

Interestingly, research also suggests your immune system may actually play a role in your social interactions, and again the link is your gut microbiome. In fact, researchers believe your immune system may actually be a controlling factor in your behavior.

Avoid processed foods — Nearly 100 trillion microorganisms compose your body's microflora, and advancing science has made it quite clear they play a major role in your health, both mental and physical. Diets loaded with processed foods lead to increased inflammation, reduced infection control, increased rates of cancer and increased risk of allergic and auto-inflammatory diseases.

Optimize your sleep — Sleeping well is one of the cornerstones of optimal health, and if you ignore your poor sleeping habits, you will, in time, pay a price. In general, you will feel best and maintain optimal health when your lifestyle is in line with your circadian rhythm. It's wise to establish healthy routines of eating, exercising and sleeping, and to stick to them every day, including the weekends.

Consider massage — Massage is often considered to be a treat reserved for special occasions, but there's good reason to make regular massages a part of your health and fitness routine. Researchers from Cedars-Sinai Medical Center revealed massages prompt significant physical changes in your body, including boosting your immune system, your body's key defense against illness and disease.

Maintain an optimistic outlook — Many studies support the belief that having an upbeat and positive attitude will translate into living a longer, healthier life and, conversely, that a pessimistic outlook promotes ill health and can shave years off your life span. For example, in one study, the tendency to always expect the worst was linked to a 25 percent higher risk of dying before the age of 65.

Learn to effectively process grief and stress — Experiencing the loss of a loved one takes a heavy toll on your emotional health, but it doesn't stop there. The extreme stress during bereavement affects you physically too, and can manifest as both chronic disease and acute illness. Stress plays a major role in your immune function, and can impact your blood pressure, cholesterol levels, brain chemistry, blood sugar levels and hormonal balance.

It is through this latter factor, hormonal balance, that grief may leave you vulnerable to infections and other illness by weakening your immune system, and it appears the elderly may be most affected.