A new research has shown that obesity limits the body’s ability to develop immunity to influenza viruses, particularly secondary infections, by inhibiting the immune system’s ability to ‘remember’ how it fought off previous similar bouts of illness.

In the study, researchers from the University of North Carolina at Chapel Hill showed that obese mice were not able to develop protective influenza-specific memory T cells.

These cells are generated by the body during an initial influenza infection. They help protect against a second infection by targeting internal proteins common among most strains of influenza viruses.

Leaner mice were able to develop the infection-fighting T cells and ward off a second bout of influenza.

“Our work suggests that obese people should be considered at high risk for infection,” said Erik Karlsson, doctoral candidate in nutrition and lead author of the study.

The researchers infected lean and obese mice with a mild influenza virus. The lean mice had been fed a low-fat diet, and obese mice had been fed a high-fat diet. When the mice recovered from the first bout of flu, they were infected a second time, with a larger dose of a more lethal influenza strain.

“We lost none of the lean mice, but 25 percent of obese mice died,” Karlsson said.

The study has been published in the March 15, 2010, issue of The Journal of Immunology.

The Journal of Immunology