English to Spanish Medical Medical (general)

To make sense of it, this is not the context but it will help those willing to help with an answer.
The adage is "Starve a fever, feed a cold." It makes sense if you think about having the flu vs. a cold. A flu is an intense reaction that takes a lot of metabolic activity. Digestion is a demanding task. As a fever is usually short lived (1-3 days), not eating may be a better way of allowing your body to contribute the maximum amount of metabolic activity to recovery. If the fever lasts longer, then maintaining adequate available energy may become a problem. Natural doctors recommend diluted vegetable (preferred) or fruit juice (unsweetened) for energy during an illness