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How can obesity affect  your immune system?

With the case of Covid-19 running around at the moment, it is important to maintain a strong immune system to protect ourselves from being infected. Today we would like to highlight the effect obesity might have on our immune system to fight off external infections.

Obesity and Immune Function

Obesity itself has been shown to impair immunity in some studies, by affecting immune cells themselves. Some of these specific findings include:

  • Decreased cytokine production

  • Altered monocyte and lymphocyte function

  • Natural killer cell dysfunction

  • Reduced macrophage and dendritic cell function

  • Decreased response to antigen/mitogen stimulation

These immune cells dysfunction leads to impaired immune response in animals and people affected by obesity, leading to increased risks of infection. The exact cause of these findings is not known. Obesity is an extremely complex disease and many processes and pathways are altered, any of which could affect the immune system.

Population studies have shown the same things. For instance, hospitalized patients affected by obesity are more likely to develop secondary infections and complications, such as sepsis, pneumonia, bacteremia, and wound and catheter infections. Overall, it appears that obesity may increase risk for bacterial and viral infections.

Malnutrition from poor diet leading to decline in immune function

We have all heard, “Eat an apple a day; you will keep the doctor away.” This is actually true. Studies do show that eating a diet that is high in fiber and antioxidants (fruits and vegetables) and has enough protein helps to keep your immune system working properly. Specific micronutrients such as iron, selenium, zinc, copper, as well as vitamins C, A, E, B-6 and folic acid have important roles in the body’s immune response.

Diets high in sugar and fat, or eating too many calories in general, make you more prone to infection. This is because it can lead to increases in blood sugar or may cause oxidative damage. Oxidative damage is an overproduction of reactive oxygen species compared to the body’s ability to detoxify cells. This type of damage from oxygen increases your chances of infection.

If you have too little protein intake, you are also at risk for protein-energy malnutrition. This has also been associated with significant impairments of immunity.

It is commonly thought that deficiencies or malnutrition cannot happen in an individual affected by obesity; however, deficiencies and malnutrition happen because of a poor diet. Therefore, deficiencies could very well occur in any individual who eats poorly, no matter their weight.

So what can you do with your diet to help your immunity?

  • If you are affected by obesity, decrease your calories to help facilitate weight-loss.

  • Decrease simple carbohydrates such as: sweets, goodies, baked goods, sugar sweetened beverages, sugar, honey, jams, jelly, etc.

  • Decrease excess “bad” (saturated or trans) fats commonly found in: commercial baked goods, processed or fried foods, cheese, whole and 2% milk, ice cream, cream, fatty meats (beef and pork products), butter and margarine. Bad fats are also found in some vegetable oils – coconut, palm and palm kernel oil.

  • Eat two cups of whole fruit per day and at least three cups of vegetables per day.

  • Drink at least 2L of water per day.

Exercise and Immune Function

Exercise and health go hand-in-hand. There is also evidence that exercise does improve immune function. Studies have shown that exercise seemed to increase numbers of certain immune cells that help to bolster immune activity.

Moderate exercise has been reported to increase certain immune cells, reducing the risk of infection. On the other hand, too intense of exercise (without adequate rest) has actually been shown to increase stress on the body and cause a person to be more at-risk to infection.

Vaccines and Obesity

Some studies have described relationships between vaccine response and obesity. A lot of work has been done regarding hepatitis B vaccines in regards to obesity, in which studies show strong evidence that individuals affected by obesity have a very high non-response rate to vaccination. This means after the introduction of the “non-active virus” to the individual’s immune systems, the disease fighting antibodies are not produced to the extent they need to be to protect against the disease.

In a person affected by obesity (body mass index [BMI] of 30-39), studies have shown that it takes a more potent hepatitis B vaccine in order to come close to the response rate of a standard single dose therapy in an individual with a BMI less than 30 (overweight).


Well known links exist between diet, exercise and immune function. Eating healthier and incorporating moderate exercise can help to increase your immune function; however, now it is known that obesity itself (diet or genetic induced) decreases immunity leading to increased risk of bacterial and viral infection as well as decreased responsiveness to some vaccinations. The exact mechanisms are not known; however, future studies will focus on this area. The good news is that several studies have shown an increase in immune responsiveness and improvements after weight-loss or following dietary restriction.

Edited from Obesity Action Coalition article , Obesity and the Immune System.

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