Crew members that are in a Torpor state will get their nutrition through a process called Total Parenteral Nutrition (TPN). With TPN the crew member will obtain all nutrients (such as glucose, amino acids, lipids, added vitamins and dietary minerals) through an intravenous (IV) line, bypassing the usual process of eating and digestion. TPN is a well-known and often used medical process for the long-term care of preterm infants and adults that are suffering from medical conditions that do not allow them eat.
The physical sensation of hunger is related to contractions of the stomach muscles. These contractions, sometimes called hunger pangs, are believed to be triggered by high concentrations of the hormones (Ghrelin is the most common) that is released if a person’s blood sugar levels get low.