What is the link between excess weight and impaired immune function?
Both human and animal studies show that obesity can lead to “altered lymphocyte numbers and reduced lymphocyte responsiveness to mitogen stimulation, dysregulated cytokine expression, decreased natural killer cells, macrophage and dendritic cell functions” (translation: A highly impaired immune system, leading to a higher risk of infection or a worse outcome).
Obesity increases the risk of hospitalization and death due to the flu. People who are overweight or obese also shed more virus particles and shed them for a longer time, endangering others. Hospitalized patients are also more likely to develop secondary infections—a problem we’re currently seeing with COVID-19— if they are obese.
Why is extra weight dangerous?
Extra weight causes inflammation.
Your subcutaneous fat (that’s “the inch you can pinch”) is healthy fat. But your visceral fat—the deep-down fat that wraps around your organs—is a witch’s cauldron that’s constantly brewing up inflammatory chemicals and releasing them into your body.
This is particularly dangerous if COVID-19 strikes, because the biggest offender in this virus is the cytokine storm that can overwhelm your body with inflammatory molecules. If you’re already chronically inflamed, this cytokine storm can hit you even harder.
Leptin resistance can occur with excess weight.
You might already know about leptin from my posts about how it helps to control appetite, but it turns out that it has another important job. Let’s start with the back story. Leptin, a hormone produced by your fat cells, tells your brain if you’re full or hungry. That’s why I call it your “hunger trigger.”
However, if you’re obese, this trigger doesn’t work right anymore. That’s because your leptin concentration correlates with your percentage of body fat. So more body fat equals more leptin. You’d think that would make you less hungry, right? But unfortunately, when your levels of leptin are always high, your brain stops listening to it. This is called leptin resistance, and it means that you’re hungry even when your body has plenty of food.
So… what does this have to do with immunity? It turns out that leptin doesn’t just affect your appetite—it affects your immune system, too. We’re learning that leptin influences an incredible range of immune system responses—both inflammatory and anti-inflammatory. Leptin resistance throws a monkey wrench into this intricate process, wreaking havoc on your immune function.
Extra weight can lead to diabetes.
Being overweight or obese dramatically increases your risk for type 2 diabetes, and infections are more common and often more serious in diabetics. One reason is that high blood sugar levels cause the body to produce molecules that weaken its infection-fighting defenses.
How can I decrease my risk?
Enough bad news—now for the good news!
But here’s the very, very good news: every pound you lose right now will improve your immune function and help to protect you against COVID-19.
In fact, one exciting study shows that even a small amount of weight loss starts to reverse immune system damage. The authors of this study found that simply losing about 13 pounds was enough to “bring the pro-inflammatory nature of circulating immune cells back to that found in lean people.” This means that you can start healing your immune system fast.
While everyone else is using this pandemic as an excuse to gain weight, use it as your motivation to LOSE weight. And while the people around you are feeling helpless, feel empowered—because this is one COVID-19 threat you can face down and crush.
