Malnutrition can be subtle in the early stages.  Even an obese animal can become quickly malnourished in the hospital when ill or injured.  If insufficient calories are supplied, the animal will lose weight but it will be functional lean body mass, rather than fat, that is lost.  A cat with asthma that is not malnourished and that is at low risk for becoming so does not require immediate nutritional support and can be monitored to ensure adequate food intake. However, if the underlying disease does not resolve quickly or the animal continues to be anorectic, nutritional support may be required.