A temporary elevation in body temperature, or fever, is a controlled physiological response the body uses to fight off infection. This defensive mechanism is often accompanied by the persistent folk wisdom that pits “feeding a fever” against “starving a fever.” Resolving this dichotomy requires moving past old adages to understand the body’s increased metabolic needs during illness, supported by modern scientific understanding. This guidance clarifies how to approach calorie and nutrient intake when experiencing a fever.
The Historical Context of the Adage
The idea of “starving a fever” has roots that stretch back to early medical theories, possibly originating with Hippocrates, who suggested that to eat when sick was to “feed your sickness.” This ancient medical philosophy believed that fever was a disease in itself and that fasting could help neutralize it. Early physicians also theorized that the process of digestion itself generated heat, which could exacerbate an already elevated body temperature.
The concept gained wider traction from the observation that appetite naturally decreases during illness. The body’s response to infection, known as “sickness behavior,” includes a reduction in the desire to eat, which was misinterpreted as the preferred, therapeutic course of action. This historical advice, however, lacked the modern understanding of the high energetic cost of an immune response.
Modern Guidance on Calorie and Nutrient Intake
The immune system requires a substantial amount of energy to mount an effective defense against pathogens. When a person has a fever, their basal metabolic rate (BMR) increases, meaning the body burns calories faster just to maintain basic functions. For every one-degree Celsius rise in body temperature, the BMR can increase by approximately 10 to 13 percent.
This heightened metabolic demand means that “starving” the body during a fever is counterproductive, as it limits the resources needed for healing. Energy restriction during illness can worsen symptoms and potentially lengthen the duration of sickness. The body requires consistent fuel to produce the new immune cells and proteins necessary to fight the infection.
Patients should focus on consuming nutrient-dense foods, even if their appetite is low. Easily digestible options, such as simple carbohydrates found in toast or rice, and soft proteins like eggs or yogurt, minimize the strain on the digestive system. Small, frequent intake of food helps to steadily supply the necessary calories.
Micronutrients also play a significant role in immune function, so incorporating sources of vitamins and minerals is important. Vitamins C and D, along with minerals like zinc, are known to support the production and function of white blood cells. Broths and soups are particularly beneficial because they provide a combination of gentle calories, proteins, and fluids in one easily consumable form.
The Essential Focus: Preventing Dehydration
While caloric intake is necessary, preventing dehydration is the most immediate concern when managing a fever. The elevated body temperature triggers the body’s cooling mechanism, which leads to increased perspiration and fluid loss through the skin. An increase in the respiratory rate, a common occurrence with fever, also causes the loss of additional water vapor through the breath.
This fluid loss is often compounded if the underlying illness involves vomiting or diarrhea, which rapidly depletes both water and electrolytes. Dehydration can worsen fever symptoms and make the body less efficient at regulating its temperature. The higher the fever, the more severe the risk of dehydration becomes.
It is necessary to continuously replace lost fluids using various sources. Plain water is always a good choice, but clear broths and electrolyte solutions are better options because they also restore lost sodium and potassium. Dark yellow urine, a dry mouth and throat, and feelings of dizziness or light-headedness are common indicators that the body needs more fluids.
Consuming at least eight glasses of fluid daily is a general recommendation, but this amount should be increased during a fever to compensate for the higher rate of loss. Seeking medical attention may be necessary if a person cannot keep fluids down or if signs of severe dehydration, such as confusion or a rapid heartbeat, appear.