Does Weight Impact Severity of Flu-Like Symptoms?

December 5, 2018

Being underweight or morbidly obese, regardless of viral pathogen status, increases the risk of being hospitalized with influenza-like illness due to flu or other respiratory viruses, according to the results of a recent study.

There is currently not enough information available on the relationship between obesity and risk of complications related to seasonal influenza and other viral causes of influenza-like illness (ILI), according to the study authors.

They conducted an observational cohort study involving 4778 participants from 6 hospitals in Mexico. The participants’ nasopharyngeal swabs were tested for influenza and other common respiratory pathogens.

Overall, 20153 of the participants had severe ILI, with 778 who were positive for influenza, 2636 positive for other viral respiratory pathogens, and 1364 with no identified respiratory viruses. Adults with influenza who were underweight (odds ratio [OR] 5.20), obese (OR 3.18) or morbidly obese (OR 18.40) were more likely to be hospitalized than normal-weight adults. Adults with H1N1 who were also obese had a 6-fold increased risk of hospitalization over H3N2 and B viruses compared with normal-weight adults (obese OR: 8.96 vs 1.35, morbidly obese OR: 35.13 vs 5.58, respectively). Among those with coronavirus, metapneumovirus, parainfluenza, and rhinovirus, underweight (OR 4.07) and morbidly obese adults (OR 2.78) were more likely to be hospitalized compared with normal-weight adults.

“In conclusion, our findings suggest that adults, who are underweight or morbidly obese, even if they do not have chronic conditions that increase the risk of influenza‐related complications, may be at increased risk of developing severe disease due to seasonal influenza infection as well as other respiratory viral infections. Clinicians should keep a patient's body mass index in mind when evaluating risk and deciding on a course of treatment.”

—Michael Potts


Moser JS, Galindo-Fraga A, Ortiz-Hernandez AA, et al. Underweight, overweight, and obesity as independent risk factors for hospitalization in adults and children from influenza and other respiratory viruses [published online December 4, 2018]. Influenza. doi:

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