Obesity has been identified as a major health concern in many countries.

According to the World Health Organization (WHO), obesity has nearly tripled since 1975, and in 2016, it was estimated that 1.9 billion adults worldwide were overweight, of which 650 million were obese. Obesity is not only a matter of aesthetics but also a complex disease that affects different organs and biological processes, including the immune system.

In this article, we will explore the link between obesity and immune system function and how this connection affects our overall health.

What is Obesity?

Obesity is a condition that occurs when a person’s body mass index (BMI) is equal to or greater than 30. BMI is calculated by dividing a person’s weight in kilograms by the square of their height in meters.

Although BMI is not a perfect measure of body fat, it is widely used to assess whether an individual is underweight, normal weight, overweight, or obese. Obesity is the result of an energy imbalance between the calories consumed and the calories expended. In other words, when we eat more calories than our body needs, the excess is stored as fat, leading to weight gain.

The Immune System

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful invaders, such as bacteria, viruses, and parasites.

Related Article Immune system dysregulation in obesity

The immune system can be divided into two main components: the innate immune system and the adaptive immune system. The innate immune system is the first line of defense against pathogens and is composed of physical, chemical, and cellular barriers that prevent or limit their entry into the body.

The adaptive immune system, on the other hand, is responsible for mounting a specific response to a particular pathogen and developing memory cells that can recognize and respond faster to future attacks.

How Obesity Affects the Immune System

Obesity is a chronic low-grade inflammatory condition that alters the immune system’s function, leading to dysregulation and impaired response to infections. Several mechanisms have been proposed to explain how obesity affects the immune system:.

1. Inflammation: Adipose tissue (fat cells) secretes several pro-inflammatory molecules, such as cytokines, chemokines, and adipokines, that can activate immune cells, including macrophages and T cells. This chronic low-grade inflammation can impair the immune response to infections and contribute to the development of metabolic and cardiovascular diseases.
2. Adipokines: Adipokines are hormones produced by adipose tissue that regulate energy homeostasis and inflammation. Leptin is an adipokine that has been implicated in the regulation of food intake and energy expenditure. However, in obesity, the leptin signaling pathway is impaired, leading to leptin resistance and the production of more leptin. High levels of leptin can trigger an inflammatory response that can harm the immune system’s function and lead to insulin resistance and metabolic dysfunction.
3. Mechanical Stress: Obesity increases the mechanical stress on the body’s joints, organs, and blood vessels, leading to inflammation, oxidative stress, and tissue damage. This can also impair the immune system’s function, as some immune cells, such as T cells, rely on physical cues to respond to infections.

Obesity and Immune System Function

The immune system’s function is impaired in obese individuals, making them more vulnerable to infections, chronic diseases, and cancers. Here are some examples of how obesity affects immune system function:.

1. Infections: Obesity is associated with an increased risk of respiratory infections, such as influenza and pneumonia. This is partly due to the impaired production of antibodies and T cells and the decreased function of natural killer cells (cells that can kill infected cells). Obesity is also a risk factor for bacterial infections, such as cellulitis and urinary tract infections, due to the impaired wound healing and the accumulation of bacteria in adipose tissue.
2. Chronic Diseases: Obesity is a risk factor for several chronic diseases, such as type 2 diabetes, cardiovascular disease, and cancer. These diseases are often associated with chronic inflammation and dysregulation of the immune system. For instance, in type 2 diabetes, insulin resistance and inflammation impair the function of immune cells, leading to a higher risk of infections and poor wound healing.
3. Cancer: Obesity is a risk factor for several types of cancers, including breast, colon, and liver cancers. The mechanisms linking obesity and cancer are not fully understood but may involve chronic inflammation, oxidative stress, and dysregulation of the immune system. For instance, obese individuals have a higher number of immune cells in adipose tissue that can contribute to inflammation and cancer development.

Conclusion

Obesity is a complex disease that affects different biological processes, including the immune system.

Obesity alters the immune system’s function, leading to dysregulation, impaired response to infections, and increased risk of chronic diseases and cancers. Therefore, maintaining a healthy weight through diet and exercise is essential for maintaining a healthy immune system and reducing the risk of obesity-related diseases.