How Your Weight Can Affect Your Immune System

A balanced diet and managing stress are key to staying healthy, but did you know body weight can also influence your immune response?

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Julia Zakrzewski, RD
— Signos
Health & Nutrition Writer
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Updated by

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Science-based and reviewed

July 24, 2024
July 27, 2022
— Updated:

Table of Contents

A Rundown of Your Immune System 

Your immune system is your body’s primary defense against sickness and harmful infections.1 It is “on” twenty-four hours a day and is actively protecting you, even while you sleep. 

The major components of your immune system include organs, cells, and proteins in your blood. When a harmful pathogen is detected, also known as an antigen, your immune response is activated.1


Essential Components 

White blood cells, specifically T cells, are the primary soldiers that fight on your immune system's behalf. They locate the harmful pathogen and work on eliminating it from the body. If this is the first time your body has encountered these new germs or viruses, it can take a bit longer to heal.1

The good news is that your immune system diligently takes notes, so if that germ ever comes back in the future, your body should know how to defend itself and heal faster. 

Autoimmune Diseases

Sometimes the immune system can get confused and attack cells in the body that are harmless. This is commonly seen in autoimmune diseases, which affect approximately 23 million Americans.2

People who suffer from autoimmune conditions often see a change in their weight as a result of their condition. Some people experience weight loss, but many people end up gaining weight which is likely due to chronic inflammation.2

Despite their best efforts, people who suffer from these conditions may have a more difficult time achieving long-term weight loss results.  

If you know that you suffer from an autoimmune condition and can not lose weight, follow up with your health care provider to discuss options suitable to your needs. 

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/ways-to-reduce-inflammation#toc-inflammation-can-cause-leaky-gut-syndrome-">the connection between gut health and autoimmune disorders</a>.</p>

What Affects Your Immune Response? 

There are several factors that can influence how well your immune system responds to potential threats: 

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/age-glucose-levels">the connection between age and blood sugar levels</a>.</p>

Does Being Overweight Affect Your Immune System? 

Undesired weight gain contributes to an increase in inflammatory responses in the body. This is because certain fat tissues, called adipose tissue, are hormonally active.3 The excess hormones directly impair immune responses, and you are less able to defend yourself from sickness or infection.4

A 2020 review confirmed that obesity impairs immune function, and increases the risk of severe infectious disease.5 There is very little evidence available on how the immune system of people who fall in the overweight category is affected. 

What If You Are Underweight? 

The CDC classifies being underweight with a body mass index (BMI) cutoff score of less than 18.56. When you are underweight your metabolism changes and your immune system is unable to function as efficiently. It can’t fight as hard to keep you healthy, and you are more likely to catch a cold that lingers. 

There are several reasons why you may become underweight. It can be unintentional, and it can be very difficult to get back to a weight where you feel your best. If you need help gaining weight in a safe and healthy way consult your care team and ask to meet with a registered dietitian. 

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/bmi">the limitations of BMI as a measurement of health</a>.</p>

three women walking down the street in summer
Measurements like waist-to-hip ratio & body fat percentage are good alternatives to BMI

How Does Losing Weight Affect Your Immune System?

Some weight loss can benefit your immune system, specifically in people who live with obesity. However, the method of weight loss can significantly impact your immune function. 

Generally, gradual weight loss is more likely to stay off and will have a less shocking impact on your immune system. 

Avoid Rapid Weight Loss Strategies 

Rapid weight loss solutions can sound something like “you will lose all your fat mass overnight!” These promises are eye-catching but they are rarely backed by science. In fact, many of these rapid solutions (anything that can produce results in less than two weeks) can actually backfire on your long-term success and weaken your immune system. 

It is well known that rapid weight loss actually increases the pro-inflammatory response in the body. An article published in 2019 showed that calorie restriction, while trying to keep up with an active weight loss exercise routine, significantly impacted the functionality of the immune system.7

The scientists observed a decrease in the total volume of immune cells present after weight loss. The study allowed for a research period for weight regain, and they found the decreased immune system response reversed, and more lymphocyte cells were present again.7

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/sustainable-weight-loss">the benefits of sustainable weight loss</a>.</p>

Bariatric Surgery 

Most of the research available investigates the immune function of people who are classified as obese. The current most effective treatment for obesity is bariatric surgery.8 After surgery, and weight loss, the immune response appears to improve, and harmful inflammatory markers in the body decline.8

A review from 2019 shows that cell populations in the body, called lymphocytes, are directly linked to the immune system change after bariatric surgery9. There is a clear decrease in pro-inflammatory markers and an increase in anti-inflammatory cells. 

These results after bariatric surgery occur due to a series of changes at the physiological and cellular levels in the body. As long as the weight loss is maintained, the results should be long-lasting. 

Can Maintaining a Strong Immune System Help You Lose Weight? 

Maintaining a strong immune system should, in theory, make it easier to lose weight. When your immune system is strong: 

  • Your appetite may be more predictable 
  • Energy levels may be more consistent 
  • Motivation to stick with your healthy eating and exercise plan may be higher

All of these actions will support your weight loss efforts and help you meet your goals. 

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/body-positivity-weight-loss">body-positive weight loss strategies</a>.</p>

Is a Weak Immune System Holding You Back from Losing Weight? 

There isn’t enough scientific evidence to prove that a weak immune system is stopping you from losing weight. Weight loss is complicated, and there are too many variables that could be impacting any results.  

It will be challenging for the scientific community to ever quantify this type of research in the future. There is a big gap in what classifies as a weak immune system. Is it how often you get sick, or how severely you are affected by a disease? 

Without this data and this insight, it is impossible to tell how significantly your immune system is affecting your weight loss efforts. 

Tips to Help You Improve Your Immune System 

  • Practice excellent sleep hygiene and make sure you get enough sleep 
  • Eat a diet rich in colorful fruits and vegetables 
  • Maintain a healthy weight 
  • Avoid harmful substances (such as tobacco products) 
  • Manage your stress and avoid physical and mental burnout 
  • Include regular physical activity and spend time outdoors 
  • Stay on top of your general health and keep up with regular checkups 

Consistently practicing healthy habits will ensure your immune system remains strong. Proactive measures are the best approach to remaining healthy. 

When you are already sick you are more susceptible to catching more germs and prolonging your sickness. Stay at home, enjoy a hot bowl of chicken soup that is high in healing vitamins, and focus your energy on recovering. 

carrots, cabbage, eggplant, tomatoes, lemons and other fruits and vegetables
Foods high in fiber and probiotics can also support immune health

Are There Any Foods That Can Help Your Immune System?

Whole unprocessed foods that are rich in vitamins and minerals will support your health. Make sure you include a variety of colored fruits and vegetables throughout the day to ensure you are meeting your nutrition requirements. 

Oranges and other citrus fruits are high in vitamin C, which is an antioxidant that supports your immune system. Other foods high in vitamin C include: 

  • Strawberries
  • Bell peppers (all colors)
  • Grapefruit 
  • Cantaloupe 
  • Kiwi
  • Blackcurrants
  • Cherries

If you regularly eat fresh fruits and vegetables you do not need to take a vitamin C supplement. 

Keep in mind no single food is better than others when it comes to supporting your immune system. They all play important roles in your health. If you absolutely detest certain foods, you may consider taking a multivitamin to cover your bases and ensure your full nutrition needs are met. 

<p class="pro-tip"><strong>Listen to a podcast about </strong> <a href="/blog/four-healthy-habits-to-bolster-your-immune-system-an-interview-with-dr-heather-moday">healthy habits for your immune system</a>.</p>

Can a CGM Device Help You Better Understand the Connection Between Weight and Immune response? 

A continuous glucose monitoring (CGM) device may provide insight into how your weight affects immune response, but it’s impossible to know for sure. The devices have never been tested or used for this type of science before, and no clinical trials exist to validate any findings. 

As you progress through your weight loss journey, you may keep track of your blood sugar levels as sickness arises. How did your blood sugar look the last time you got sick? You can use this data to look for patterns and make comparisons. 

Continual, real-time blood sugar readings from a CGM can also help deepen your understanding of how your body operates while sick or healthy. Are there certain foods you metabolize better when you are healthy compared to when you are sick? All this information can help you personalize your lifestyle choices so you can stay aligned with your overall health goals. 

<p class="pro-tip"><strong>Learn more about </strong> <a href="/blog/blood-sugar-immune-system">how blood sugar affects your immune system</a>.</p>

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Topics discussed in this article:


  1. [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does the immune system work? [Updated 2020 Apr 23]. Available from: 
  2. US Department of Human Health and Services. (2005). Progress in Autoimmune Diseases Research. Retrieved from: 
  3. Coelho, M., Oliveira, T., & Fernandes, R. (2013). State of the art paper Biochemistry of adipose tissue: an endocrine organ. Archives of Medical Science, 2, 191–200. 
  4. Honce, R., & Schultz-Cherry, S. (2019). Impact of Obesity on Influenza A Virus Pathogenesis, Immune Response, and Evolution. Frontiers in Immunology, 10. 
  5. de Frel, D. L., Atsma, D. E., Pijl, H., Seidell, J. C., Leenen, P. J. M., Dik, W. A., & van Rossum, E. F. C. (2020). The Impact of Obesity and Lifestyle on the Immune System and Susceptibility to Infections Such as COVID-19. Frontiers in Nutrition, 7. 
  6. All About Adult BMI. (2022, June 3). Centers for Disease Control and Prevention. Retrieved July 2022, from 
  7. Sarin, H. V., Gudelj, I., Honkanen, J., Ihalainen, J. K., Vuorela, A., Lee, J. H., Jin, Z., Terwilliger, J. D., Isola, V., Ahtiainen, J. P., Häkkinen, K., Jurić, J., Lauc, G., Kristiansson, K., Hulmi, J. J., & Perola, M. (2019). Molecular Pathways Mediating Immunosuppression in Response to Prolonged Intensive Physical Training, Low-Energy Availability, and Intensive Weight Loss. Frontiers in Immunology, 10. 
  8. Villarreal-Calderón, J. R., Cuéllar, R. X., Ramos-González, M. R., Rubio-Infante, N., Castillo, E. C., Elizondo-Montemayor, L., & García-Rivas, G. (2019). Interplay between the Adaptive Immune System and Insulin Resistance in Weight Loss Induced by Bariatric Surgery. Oxidative Medicine and Cellular Longevity, 2019, 1–14. 
  9. Villarreal-Calderón, J. R., Cuéllar, R. X., Ramos-González, M. R., Rubio-Infante, N., Castillo, E. C., Elizondo-Montemayor, L., & García-Rivas, G. (2019b). Interplay between the Adaptive Immune System and Insulin Resistance in Weight Loss Induced by Bariatric Surgery. Oxidative Medicine and Cellular Longevity, 2019, 1–14.

About the author

Julia Zakrzewski is a Registered Dietitian and nutrition writer. She has a background in primary care, clinical nutrition, and nutrition education. She has been practicing dietetics for four years.

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