For every degree your body temperature climbs when sick, the body expends more energy (via Scientific American). While you may have little desire to eat when feeling under the weather, research has shown that fueling our body with food better equips us to fight off infection. This was demonstrated in a series of rodent studies conducted by Michigan State University nutritional immunology professor Elizabeth Gardner. In a 2005 study published in The Journals of Gerontology, the Michigan State University study team found that 22-month-old mice who were given a calorie-restricted diet and exposed to the flu virus were less likely to survive the infection than mice who freely consumed food. A calorie-restricted diet was also linked with increased viral concentration and suppressed activity of natural killer cells in the animals’ lungs. Three years later, a 2008 study published in The Journal of Nutrition proved similar findings for younger mice that were six months of age.
“Our research shows that having a body ready to fight a virus will lead to a faster recovery and less-severe [sic] effects than if it is calorically restricted,” Gardner told MSU Today. “Adults can calorically restrict their diet eight months out for the year, but during the four months of flu season they need to bump it up to be ready. You need the reserves so your body is ready for any additional stress, including fighting a virus.”