Most commentators note that food is not usually urgently needed in survival situations because a human can survive for several weeks without it. However, they also note that in extreme cold lack of food can be dangerous, and in other situations hunger, like gradual dehydration, can bring about many consequences long before it causes death, such as:
* Irritability and low morale
* Loss of mental clarity, such as confusion, disorientation, or poor judgment
* Weakened immune system
* Increasing difficulty maintaining body temperature (see Heat exhaustion and Hypothermia)
To thus avoid these problems, culinary root tubers, fruit, edible mushrooms, edible nuts or edible leaves, edible moss, edible cacti and algae can be searched and if needed, prepared (mostly by boiling). With the exeption of leaves, these foods are relatively high in calories, providing some energy to the body.
Also, many commentators discuss the knowledge, skills, and equipment (such as bows, snares and nets) necessary to gather animal food in the wild through animal trapping, hunting, fishing..
Some survival books promote the "Universal Edibility Test". Allegedly, one can distinguish edible foods from toxic ones by a series of progressive exposures to skin and mouth prior to ingestion, with waiting periods and checks for symptoms. However, many other experts including Ray Mears and John Kallas reject this method, stating that even a small amount of some "potential foods" can cause physical discomfort, illness, or death. An additional step called the scratch test is sometimes included to evaluate the edibility of a potential food.
Focusing on survival until rescued by presumed searchers, The Boy Scouts of America especially discourages foraging for wild foods on the grounds that the knowledge and skills needed are unlikely to be possessed by those finding themselves in a wilderness survival situation, making the risks (including use of energy) outweigh the benefits.