Commentary and supervision:
Dr. Yoshihiro Kitamura
Deputy Director of the Center for Medical Education,
Nippon Medical School,
and Specially Appointed Professor.
Doctor of Medicine

What is the relationship between obesity and immunity?

In recent years, the relationship between fat-especially visceral fat-and immunity has been the focus of much attention. In the bodies of people with visceral-fat obesity, the balance of hormones secreted by visceral adipose tissue is disturbed, resulting in a state of persistent systemic inflammation, or "chronic inflammation". This chronic inflammation leads to a decline in immune function, which in turn leads to infections becoming severe and other problems.

You say that obesity is an inflammatory condition, but that's hard to visualize...

Unlike so-called acute inflammation, in which the affected area swells and turns red when a foreign enemy such as bacteria or a virus invades, chronic inflammation is a state in which the immune system is in constant battle-mode even though there is no enemy from the outside. The immune system, which was originally supposed to fight enemies from the outside, is malfunctioning in a runaway state even though there are no enemies present, so it's in a doubly-bad state because it's not only weaker when it comes time to fight outside enemies but it also damages your own normal cells. So, conversely, it can be said that eliminating the inflammatory condition of obesity leads to an increase in immunity.

What are the actual dangers when bacterial and viral infections occur in people with obesity?

In a report on COVID-19, it was found that "people with obesity have a higher rate of ICU admission and a higher rate of severe illness than people of normal weight."
When a person with obesity is infected with the virus, chronic inflammation within the visceral adipose tissue rapidly worsens. Cytokines, proteins that activate immune cells, are released explosively, and as I mentioned earlier, the immune system goes into a runaway state. This is called a cytokine storm. Overly activated immune cells attack your own normal cells as well, leading to more severe infections.

We often hear that obesity causes lifestyle-related diseases, but I never knew that it also lowers immunity.
You become more susceptible to infections.

That's right. But in addition to fighting bacteria and viruses, the immune system also plays an important role in repairing aging cells and tissue damage. When immune function is degraded or out of control due to chronic inflammation, this role is also compromised. Blood vessels throughout the body also age more rapidly, and your face looks older, with more wrinkles and spots than normal for your age.

That's frightening... So immunity is also important for anti-aging!

Yes it is. As we have explained, visceral fat and immunity affect each
other, so optimizing them at the same time is quite a powerful technique
for better health. It is very important to improve eating habits and to incorporate an appropriate level of exercise.

Many people are concerned about unbalanced diets and lack of exercise due to remote work. Let's start by improving eating habits, and begin light exercise such as walking and calisthenics! Sometimes, a good supplement focused on visceral fat and immunity care can help the body to resist both infections and
lifestyle-related diseases.