How Excess Body Fat can Sabotage the Immune System
We know obesity is linked with various other chronic diseases - diabetes, heart disease, hypertension, sleep apnea, fatty liver disease, and even cancer. Did you know obesity can also sabotage the immune system? Several studies in both humans and animals show strong evidence that obesity (or excess body fat) can weaken the immune response, increasing susceptibility to infection.
For starters, a common factor leading to obesity is a poor diet. A poor diet is low in micronutrients that play essential roles in the immune response - vitamins A, B6, C, E, folate, copper, iron, selenium, and zinc. Some other possible mechanisms and reasons, as highlighted in a journal review in The Proceedings of the Nutrition Society1, include:
- supressed T- and B- cell function 2
- reduced potency of natural killer cells
- reduced cytokine production (substances secreted by certain immune system cells)
- the immune cells may be desensitized to the normal inflammatory response of a real infection because it is always exposed to a low-grade chronic inflammation associated with obesity 11
- reduced macrophage function
- loss of lymphoid tissue integrity
- decreased response to antigen stimulation
- increased length of stay at hospitals
- increased risk of post-operative complications
- obesity leads to fat depositing in tissues of the immune system, such as the bone marrow and thymus. A change in the architecture of these tissues interferes with proper development of leukocytes ( a type of immune cell) 15
While we won't go into detail about what all these different findings mean, the main message is that obesity can compromise immune function. Numerous reports link obesity to a significantly increased risk for post-operative infections, periodontal infections, respiratory infections, and nosocomial infections (infections obtained in the ICU). 3-6
Interestingly, a significant number of studies reported obesity was a main predictor of poor outcomes during the 2009 H1N1 pandemic. 7 This led researchers to examine the link between obesity and the seasonal flu. It turned out obese individuals (with and without chronic health problems) were at an increased risk of being hospitalized for the seasonal flu.8
Vaccines & Obesity
In fact, there is accumulating evidence that obese individuals don't respond to vaccines and antibiotics the same as healthy-weight individuals. For example, studies have shown this to be the case with hepatitis B vaccination, the influenza vaccine, rabies and tetanus shots in children. 9,10, 13, 14, 16
Does Weight Loss Really Help Improve Immunity?
Most studies on the connection between obesity and impaired immunity acknowledge that, within the limits of their studies, healthy weight loss to achieve a healthier weight and body fat percentage can help improve immunity. One study put 100 Hepatitis C virus (HCV) patients in Saudi on a weight loss proram and examined how this affected their immunity. Results showed significant changes in their white blood cell, neutrophil, monocyte, CD3, CD4, and CD8 counts. 12
As aforementioned, the exact mechanism of how obesity impairs the immune system is complex and not fully understood 100%.
Still, we do know there is a clear link between a healthy diet, exercise, and a healthy immune system. Also, several studies have shown that even modest weight loss in obese individuals already shows signs of better immune function. 17 One of the main ways this occurs is by giving the immune system a break from excessive inflammation.
Assessing Your Weight
The BMI system uses a ratio of height to weight to assess someone's weight. This system has its limitations since it cannot take into account lean body mass, genes, and the actual percent of body fat an individual has. In some cases, one in the "normal" BMI range may have significant health risks. On the flipside, someone slightly in the underweight or overweight category isn't necessarily in danger. This number needs to be taken into consideration with several other factors, such as gender, age, weight history, and other factors. In other words, the BMI system is just a guideline.
References
1. Milner JJ, Beck MA. The impact of obesity on the immune response to infection. Proc Nutr Soc. 2012;71(2):298-306. doi:10.1017/S0029665112000158
2. Nieman, D. C., Henson, D. A., Nehlsen-Cannarella, S. L., Ekkens, M., Utter, A. C., Butterworth, D. E., & Fagoaga, O. R. (1999). Influence of obesity on immune function. Journal of the American Dietetic Association, 99(3), 294–299. https://doi.org/10.1016/S0002-8223(99)00077-2
3. Vilar-Compte, D., Mohar, A., Sandoval, S., de la Rosa, M., Gordillo, P., & Volkow, P. (2000). Surgical site infections at the National Cancer Institute in Mexico: a case-control study. American journal of infection control, 28(1), 14–20. https://doi.org/10.1016/s0196-6553(00)90006-3
4. Ylöstalo, P., Suominen-Taipale, L., Reunanen, A., & Knuuttila, M. (2008). Association between body weight and periodontal infection. Journal of clinical periodontology, 35(4), 297–304. https://doi.org/10.1111/j.1600-051X.2008.01203.x
5. Jedrychowski W, Maugeri U, Flak E, Mroz E, Bianchi I. Predisposition to acute respiratory infections among overweight preadolescent children: an epidemiologic study in Poland. Public Health. 1998;112(3):189-195. doi:10.1038/sj.ph.1900438
6. Dossett LA, Dageforde LA, Swenson BR, et al. Obesity and site-specific nosocomial infection risk in the intensive care unit. Surg Infect (Larchmt). 2009;10(2):137-142. doi:10.1089/sur.2008.028
7. Jain, S., & Chaves, S. S. (2011). Obesity and influenza. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 53(5), 422–424. https://doi.org/10.1093/cid/cir448
8. Kwong, J. C., Campitelli, M. A., & Rosella, L. C. (2011). Obesity and respiratory hospitalizations during influenza seasons in Ontario, Canada: a cohort study. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 53(5), 413–421. https://doi.org/10.1093/cid/cir442
9. Weber, D. J., Rutala, W. A., Samsa, G. P., Santimaw, J. E., & Lemon, S. M. (1985). Obesity as a predictor of poor antibody response to hepatitis B plasma vaccine. JAMA, 254(22), 3187–3189.
10. Eliakim, A., Schwindt, C., Zaldivar, F., Casali, P., & Cooper, D. M. (2006). Reduced tetanus antibody titers in overweight children. Autoimmunity, 39(2), 137–141. https://doi.org/10.1080/08916930600597326
11. Ziegler-Heitbrock, H. W., Wedel, A., Schraut, W., Ströbel, M., Wendelgass, P., Sternsdorf, T., Bäuerle, P. A., Haas, J. G., & Riethmüller, G. (1994). Tolerance to lipopolysaccharide involves mobilization of nuclear factor kappa B with predominance of p50 homodimers. The Journal of biological chemistry, 269(25), 17001–17004.
12. Abd El-Kader, S. M., & Al-Jiffri, O. H. (2018). Impact of weight reduction on selected immune system response among Hepatitis C virus Saudi patients. African health sciences, 18(2), 417–427. https://doi.org/10.4314/ahs.v18i2.27
13. Bandaru P, Rajkumar H, Nappanveettil G. The impact of obesity on immune response to infection and vaccine: an insight into plausible mechanisms. Endocrinol Metab Syndr 2013;2:2.
14. heridan PA, Paich HA, Handy J, Karlsson EA, Hudgens MG, Sammon AB, Holland LA, Weir S, Noah TL, Beck MA. Obesity is associated with impaired immune response to influenza vaccination in humans. Int J Obes (Lond) 2012;36:1072–7.
15. Kanneganti TD, Dixit VD. Immunological complications of obesity. Nat Immunol 2012;13:707–12.
16. Weinberger B (ed): Vaccines for Older Adults: Current Practices and Future Opportunities. Interdiscip Top Gerontol Geriatr. Basel, Karger, 2020, vol 43, pp 86–97
17. A. Viardot, R. V. Lord, K. Samaras. The Effects of Weight Loss and Gastric Banding on the Innate and Adaptive Immune System in Type 2 Diabetes and Prediabetes. Journal of Clinical Endocrinology & Metabolism, 2010; DOI: 10.1210/jc.2009-2371