How Body Fat Sabotages Your Immune System

Published on May 05, 2016 by Ryan Walters


If there’s one thing everyone can agree on, it’s that no one likes being sick. When you’re sick, you’re not at your best, and it can feel like the time you spend being sick is time that gets taken away from you for no reason.

What if there was something you could do to be sick less often? What if it was something you had control over, something about your body that you could influence to feel better and protect against disease?

As it turns out, having a healthy body composition contributes to a healthy immune system, helping you to resist minor infections and reduce your risk of getting serious diseases, like heart disease and diabetes.

What’s a healthy body composition?  Although hard to pin down exactly, you can think of it as having sufficiently developed muscle mass and a body fat percentage under a certain limit (20% for men; 28% for women). Another, while not completely perfect, way to picture a healthy body composition is something you would expect an athlete to have - lots of muscle compared to little fat. Something that resembles this:

However, it’s safe to assume that most people don’t have bodies with these numbers. With over 1/3 of Americans classified as obese and 2/3 being either overweight or obese, we’re accumulating more fat on our bodies than any other time in history.

How does this tie into the immune system and being less sick?  It all has to do with the nature of body fat, and the effect it has on your body outside of just being extra weight.

What Happens When Your Immune System Activates

When your body gets sick – due to a bacterial infection, a virus, etc. – the immune system gets triggered, and one of the earliest signs of this triggering is inflammation.  This is thanks to your “innate” immune response: your body’s all-purpose defense mechanism that serves as the first wave of defense against foreign invaders.

If you’ve ever been sick, you’ve experienced inflammation. The infected area becomes red and swollen due to increased blood flow, which can be unsightly and uncomfortable. Think of what happens to your nose when you get a cold. That’s inflammation.

Inflammation happens appearance of white blood cells called macrophages and the proteins they emit called cytokines (this word will be important in a minute). These cytokines encourage inflammation.

You may have not thought of it this way before, but inflammation that’s triggered by your immune system is typically a good thing. That means your body is releasing the appropriate hormones and proteins, activating your white blood cells to start the recovery process, and working to defeat the infection.  If your body wasn’t becoming inflamed, you’d be in serious trouble.

So if inflammation is what naturally occurs when your body’s immune system is triggered, what does inflammation have to do with body fat, body composition, and obesity? A lot.

When Inflammation Becomes Permanent

When white blood cells cause inflammation, it’s a sign that your body’s immune system is properly functioning.  Inflammation begins, white blood cells attack the foreign invader, the invader is neutralized, and the inflammation disappears.

This is how it’s supposed to work in a properly functioning immune system. However, white blood cells aren’t the only type of cell that have the ability to emit cytokines.  A second type of cell that can emit cytokines and cause inflammation are adipose cells, which make up what we know as body fat.

It’s tempting, even natural, to think of your body fat as energy storage deposits.  Most everyone understands that when you eat more calories than your body needs, your body stores the excess calories as fat so that you can use it later for energy if food becomes scarce.  Basic evolutionary stuff, right?

Up until fairly recently, no one would have questioned you on that. However, scientists have learned that body fat is an active endocrine organ, one that can secrete a whole host of proteins and chemicals, including inflammatory cytokines.

What happens when your body keeps adding on more and more adipose tissue, as what happens when you become obese?  More and more cytokines are released by your fat cells, triggering more and more inflammation.  In fact, when obesity is viewed from an immune system perspective instead of a body weight one, it is commonly understood by researchers as: “characterized by a state of low-grade, chronic inflammation.”

Low-grade, chronic inflammation. This means that increased fat cells puts your body in a constant state of stress/immune response. Your body is always slightly inflamed; your immune system is permanently “switched on.”

Think of your body’s immune system like your body’s crack team of defenders, highly trained and designed to repel any and all foreign invaders.  In this scenario, your body fat cells are like enemy agents planted in your home territory. Their mission is to spread fear of an attack at all times, and they trick your defenders to be on high alert at all times.

As you might have guessed, perpetual, never-ending inflammation isn’t good for the body.

Sabotaged Immune System

Obesity causes a state of chronic inflammation, and this causes your immune system to become compromised.  Chronic inflammation is a serious deal and can lead to the development of illnesses large and small over time.  Here are a couple examples:

  • Influenza (the flu)

You may remember several years ago that there was a particularly deadly strain of the flu virus called H1N1.  As hospitals started to fill up with the sick, doctors in Spain noticed something: overweight and obese patients were beginning to show up in disproportionate numbers in intensive care units, and they were staying for longer than people who were not obese. Increased inflammation due to increased pro-inflammatory cytokines appeared to be a leading factor contributing to their increased flu risk.

Stories like these led  researchers in Canada to analyze the flu records for the previous 12 years, stretching from 2008 back to 1996. They found that people who were obese were more likely to come into the hospital for respiratory diseases than those who were not obese. They concluded that obese people were an “at risk” population during flu seasons due to their compromised immune response

  • Heart Disease

Heart disease is the leading killer of adults in the United States.  Although there are many factors that can contribute to heart disease, recent research has pointed to inflammation caused by obesity as one of the most significant factors contributing to its development.

The main culprits are, again, the cytokines produced by excess fat in the body.  These cytokines cause inflammation of the walls of your arteries, causing damage to the arteries and increasing pressure on your heart.  When your heart has to work harder to pump blood, it starts to enlarge. An enlarged heart is a classic symptom of heart disease that can lead to heart failure if steps aren’t taken to reduce pressure on it.

  • Diabetes

Diabetes is characterized by insulin resistance – the inability of your body to remove excess sugar from your blood. Just as with heart disease, there are many intertwined factors that lead to the onset of type 2 diabetes, and obesity has long been associated with its development.

However, with the discovery that fat is an active tissue that can secrete cytokines and wreak havoc on the immune system, researchers have been able to show a link between obesity, inflammation, and insulin resistance. Increased inflammation was shown to disturb a whole host of processes and hormonal systems in the body, which, when left unchecked for long periods of time, led to the development of insulin resistance, and eventually diabetes.

Who’s At Risk?

This isn't just something for overweight people to worry about.

Many people know that being overweight and obese is unhealthy and can lead to serious diseases over time.  Admittedly, poor diet and low levels of activity contributing to heart disease and diabetes over time in obese people isn’t exactly news.

Unless you start to take into account what the word “obese” actually means.

Classically, obesity has been defined by having a high Body Mass Index (BMI), a way of expressing the relationship of your weight vs. your height.  If your BMI exceeds 25, you’re labeled “overweight,” and once your BMI increases beyond 30, you progress into different levels of obesity.

This is the way doctors have been diagnosing people with obesity for years, but unfortunately, BMI has led to confusion by inappropriately labeling people as obese when they are not, or healthy when they should be aware of their obesity risks.

Obesity doesn’t always simply mean “fat.” What obesity does mean is the excess accumulation of body fat, but what’s excess for you might not be for someone else. It is possible to have a “normal” BMI but a lot of excess fat; this is called being “skinny fat.”  Crucially, skinny fat people share many of the same metabolic risks as people who have high BMIs, including the risk of inflammation and a faulty immune system.

This is why you should look at having too much body fat not only as a problem for people who are visibly overweight, but also for people who don’t have enough muscle relative to how much body fat they have.

One way to determine whether you’re at risk is to have your body composition determined.  This will reveal your body fat percentage, a number that you can use to understand if the amount of fat you have is healthy or excessive for someone of your size.

How To Get Your Immune System Back In Line

Fortunately, because researchers have been able to identify body fat (and particularly, internal visceral fat)  as a major cause of inflammation and a compromised immune system, they’ve also been able to measure improvements when body fat is reduced. The goal to getting your immune system to function properly again is to stop it from being perpetually triggered.

In a study that followed obese patients who lost weight with caloric restriction and bariatric surgery, the researchers observed a significant reduction in immune system activation, which means less inflammation.  This reduction in immune activation occurred before and after surgery, which indicates that surgery isn’t always necessary: just the reduction of fat mass – and specifically, visceral fat.

Improving your body composition through a mix of strategies that promote fat loss and muscle gain can allow you to reduce your fat mass in a healthy manner that doesn’t require drastic measures like bariatric surgery.  Although this process can and will take time, the effects of having an improved and healthy body composition are immense, not the least of which is reducing overall body inflammation and having your immune system function properly again.

Healthy Immune System, Healthy Life

We’ve gone over a lot of very technical stuff here, so let’s go over the main points for you to take away.

  • Excess Body fat sabotages your immune system by leaving it permanently triggered
  • Inflammation caused by body fat makes you sicker and more vulnerable to disease
  • You can reduce and reverse these changes by reducing your body fat
  • Anyone can be at risk, depending on their body fat percentage, not their weight

No one likes being sick, and no one likes having to manage diseases that stick around for a lifetime. To help you avoid these problems, one of the best ways to determine if your body fat is excessive and/or causing inflammation is to have your body fat percentage determined.

Once you have your body fat percentage, you can compare it against the normal ranges for men and women.  For men, you’ll want to be no higher than about 20% body fat; for women, try to stay under about 28%.  These ranges may vary slightly depending on whichever source you consult, but these are good guidelines and agree with the ranges set by the American College of Sports Medicine and American Council on Exercise.

Far from just being something to worry about during beach season, building a leaner body can significantly improve your quality of life by helping you stay healthy with a properly functioning immune system. Having a killer “beach bod” may not motivate you, but what about being less sick?

Everyone should see the value in that.

Tagged: Body Composition › Health/Fitness ›



Ryan Walters
Ryan Walters | Author
Ryan is a Digital Marketing Specialist at InBody USA. To get in touch with Ryan regarding this article, you can reach out at ryan@inbodyusa.com



Sign up for weekly blog updates