An interconnected system
Dr. Gregory Poland’s obese patients know they’re at risk for heart disease and diabetes, and they’ve heard their weight could doom them to an early death. But few recognize just how vast an impact obesity has on all their body systems — from their brains to their skin to their immune systems, which Poland studies at the Mayo Clinic in Rochester, Minnesota. “The human body was designed to be elegantly redundant and interconnected,” he says. In effect, obesity leaves no system untouched. Here are eight lesser-known ways it leaves its mark on the immune system:
1. It weakens your immune responses.
Think about the immune system as a three-brigade army: The front-line system, also known as the innate immune system, first fights against invaders without knowing their specific identity. Next, the adaptive immune response makes antibodies to protect against future invaders. At the same time, the body develops memory cells to help recognize the same pathogen in the future. On all three levels, obese people’s systems are weaker, says Poland, a professor of medicine and infectious diseases at the Mayo Clinic, where he also directs the Vaccine Research Group. “That whole system is suppressed and broken in obese people,” he says. “It’s a very, very difficult problem.”
2. It makes you more prone to infections.
Whether recovering from a scrape or a surgical incision, obese people’s cuts can more easily lead to infection — particularly if they’re severely obese, says Dr. Aaron Glatt, an infectious disease specialist and chairman of the Department of Medicine at South Nassau Communities Hospital in Oceanside, New York. “Sometimes the layers of fat prevent the healing from easily occurring; sometimes the wound can’t be kept clean,” he says. That’s why it’s important for medical staff to keep an eye on obese patients’ blood sugar levels (higher levels can compromise healing), even if they don’t have diabetes, Glatt says.
3. It contributes to the development of autoimmune disorders.
Poland calls it the “Goldilocks dilemma” — the idea that the immune system is supposed to maintain a balance between responding “vigorously” to external threats like infection-causing pathogens and giving its own body’s cells a free pass. But in obese people, Poland says, “that balance is turned upside down.” As a result, obese people are more susceptible to autoimmune disorders such as rheumatoid arthritis and diabetes, he says. Other research also implicates obesity in the development of Crohn’s disease and multiple sclerosis.
4. It makes you more susceptible to colds.
At the same time, while the immune system is on overdrive in obese people when it doesn’t need to be, it’s left under-responding to real threats like an everyday cold. “[My obese patients] will acknowledge … that they seem to get more colds, and the colds seem to hang on longer,” Poland says. And they’re right. To make it worse, obese people with colds typically aren’t treated like other immune-compromised populations, such as children, the elderly and people with bone marrow transplants. “They don’t get the health care they deserve to have given the risk,” Poland says.
5. … and the flu.
Just how much obesity affects the immune system became clear during the 2009 H1N1 pandemic. “Obesity turned out to be a very clear-cut risk factor for severe infection in both children and adults, and it was a clear-cut risk factor for an increased risk of death,” Poland explained to a group of journalists at an obesity fellowship program in February. Specifically, adults with body mass indexes over 30 were 3.1 times more likely to die from the infection than people of lower weights, while adults with body mass indexes over 40 were 7.6 times more likely to die.
6. … and pneumonia.
It doesn’t stop there: Flu complications, like pneumonia, are more likely among obese people, in part because obesity can make it difficult to take deep breaths — part of the reason obese people are also more prone to sleep apnea. “The chest pad prevents them from ventilating, particularly when they’re lying in a hospital bed,” Poland explained in February. Meantime, the belly’s pressure on the abdomen pushes up the diaphragm, limiting the lung’s expansions and contractions. “And when those secretions pool into the lungs,” he says, “pneumonia results.”
7. It lowers the flu vaccine’s effectiveness.
If we know obesity makes you more prone to infections like the flu, can’t we just double-down on efforts to get that population vaccinated? Fat chance. As it turns out, vaccines are generally less effective among people with obesity for the same reason they’re more susceptible to diseases in the first place: Their bodies are in a constant state of “immunodeficiency,” Poland explains. In some ways, obese people’s immune systems, he’s found, actually look like those of older adults. “That shocked us,” he says, “and may be among the reasons they can’t respond to these vaccines.”
8. … as well as other vaccines’ effectiveness.
It’s not just the flu vaccine that’s compromised by obesity. Other research has found that hepatitis A and B, as well as tetanus shots, are less effective in obese people. When it comes to the HPV vaccine, it’s not only less effective, but obese people are less likely to adhere to the three-dose schedule, although no one knows why, Poland says. Some vaccine resistance might have to do with needles that aren’t long enough to cut through the fat and reach the muscle. “There is no dosing recommendation or specific vaccines that have been devised for the obese,” Poland says. “I think the reality is, we’re going to have to.”
A solution in sight?
Meantime, Poland has a few tips for obese patients who are trying to lose weight — a goal that can boost the immune system, in addition to delivering other health benefits. Eat with chopsticks, which forces you to slow down and recognize when you’re full, he suggests; shop the perimeter of the grocery store (where the fresh produce resides) and make time to move every day. “Everything in moderation,” Glatt adds. And while you work the weight off, don’t forget to wash your hands frequently and thoroughly — a practice that can save normal-weight people up to two episodes of respiratory disease and one episode of vomiting or diarrhea a year. “So in some ways,” Poland says, “it’s even more important that obese people wash properly.”
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