How diet and metabolic health determine effectiveness

Researchers note that obesity is associated with an increased risk of serious infectious diseases, including the flu.

While this increased risk makes it more important for this group to get vaccinated, researchers note that obesity can also decrease the effectiveness of flu vaccines.

For the study, they tested a few different scenarios to see if dietary changes helped before and after vaccination.

They took two groups of mice and fed one of them a lean diet and the other a high-fat diet. The mice then received a flu vaccine. After vaccination, some mice on a high-fat diet were switched to the control diet. The mice were then given a lethal dose of the influenza virus, homotypic H1N1, after 4 or 12 weeks of a control diet.

The researchers found that switching to a healthy diet after vaccination did not improve survival despite the weight loss that the previously obese mice experienced.

Previously obese mice had only a 24% survival rate after 4 weeks on the control diet and a 28% survival rate after 12 weeks on the control diet. However, the results suggested that dietary changes to lose weight after vaccination may help control viral spread.

The results were very different when dietary changes were made before vaccination. To test this, the researchers had certain obese mice switch to the lean control diet 4 weeks before vaccination. This change allowed several systemic measures of metabolic dysfunction to return to normal and weight loss to occur.

The researchers observed an improved immune response in these mice, particularly among their T cells, and a decrease in morbidity and mortality.

After exposure to the flu virus, previously obese mice had a 100% survival rate. The results suggest that specific dietary changes and weight loss may help improve the effectiveness of the flu vaccine.

The research also expands what we know about how obesity can affect the immune response, which will be an area of ​​continued research.

“We have known since the 2009 H1N1 flu epidemic that people with obesity are at increased risk of severe flu and death, and we have seen similar findings with COVID-19. However, it’s not entirely clear why: it could be due to decreased lung function and/or other factors,” said study author Marci Drees, MD, director of infection prevention and hospital epidemiologist at ChristianaCare. Medical news today.

“It’s important to remember that this study was done in mice, and of course mice are not humans, so it’s certainly not definitive in terms of proving that people with obesity don’t respond as well to flu vaccines,” Drees said.

The main limitation of the study is that it was conducted in mice, meaning more research is needed before these findings can be applied to humans.

The researchers also note that they were limited in their ability to determine certain factors because they had a low sample size of mice on a high-fat diet that survived flu exposure. They recognize the need for further investigation of how nutrition affects immune cell function during vaccination and infection.

“There have been some small studies in the past that showed that people with obesity were more likely to get the flu, even if they were vaccinated, compared to vaccinated people who were not obese, and despite having good levels of antibodies against the flu. flu strains in the world. vaccines that year,” Drees said.

“There is much more to study in this area to better understand the interactions between obesity, the flu virus and the flu vaccine.”

Dr. Linda Yancey, director of infection prevention at Memorial Hermann Health System in Houston, who was not an author of the study, said: TMN:

“First of all, this is a mouse study. Needless to say, mice are not people. This seems like a good foundational study on which to base future human trials. Studies like these are more important than many people realize because they demonstrate something everyone generally agrees on: a healthy diet and weight loss are good for your health. While we all believe this to be true, it is good to see solid scientific data to back it up.”

The findings show that a healthy diet could affect the effectiveness of the vaccine, but this does not mean that people with obesity should avoid vaccination.

As the Centers for Disease Control and Prevention (CDC) As he points out, people with a body mass index (BMI) of 40 or higher may be at higher risk of complications from the flu. Therefore, vaccination could be even more important in this demographic.

People can talk to their doctors about personal risk factors that may increase complications if they get the flu. They can also discuss any potential risks from the vaccine itself and how effective it may be for them.

While the study will not lead to immediate changes in clinical practice or recommendations, health professionals generally encourage weight loss among obese people.

“(The study) will need to be followed by a human trial to see if the observation holds,” Yancey said.

“If so, then we might recommend a healthy diet and weight loss in the weeks before vaccination. However, this is already a general recommendation for everyone. Therefore, there would be no major changes to general health advice.”

Dress said he would not change any current recommendations based on this mouse study, noting the following:

“Losing weight has many health benefits, and a better response to vaccines could be one of them. But that’s really just a theory at this point. I would definitely still strongly promote the flu vaccine regardless of your weight, and I would probably recommend it even more in people who are obese because we know that their risk of getting severe flu is higher.

So, I wouldn’t want someone to not get vaccinated because they think the flu shot won’t work for them; There is also good evidence that even if you get the flu after getting vaccinated, your risk of serious illness and death is lower. . “People living with obesity should talk to their doctor about their weight loss options, but should still get an annual flu vaccine.”