Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life.

[5] The results also demonstrates that as global hunger levels have stabilized, however, despite some progress in specific areas such as stunting and exclusive breastfeeding, an alarming number of people still face food insecurity and malnutrition.

The exact pathogenesis of kwashiorkor is not clear, as initially it was thought to relate to diets high in carbohydrates (e.g. maize) but low in protein.

Possible causes such as aflatoxin poisoning, oxidative stress, immune dysregulation, and altered gut microbiota have been suggested.

[8] Treatment can help mitigate symptoms such as the pictured weight loss and muscle wasting, however prevention is of utmost importance.

Females may survive longer than males due to their higher body fat content at the same BMI.

These symptoms show up as irritable and/or unstable mood, fatigue, trouble concentrating, and preoccupation with food thoughts.

It usually takes days to weeks, and includes weakness, fast heart rate, shallow breaths that are slowed, thirst, and constipation.

Symptoms of starvation may also appear as a weakened immune system, slow wound healing, and poor response to infection.

Phase one: When meals are skipped, the body begins to maintain blood sugar levels by degrading glycogen in the liver and breaking down stored fat and protein.

The body uses fatty acids as an energy source for muscles but lowers the amount of glucose sent to the brain.

The final stage of starvation includes signals like hair color loss, skin flaking, swelling in the extremities, and a bloated belly.

Even though they may feel hunger, people in the final stage of starvation usually cannot eat enough food to recover without significant medical intervention.

Glycogen is a readily-accessible storage form of glucose, stored in notable quantities in the liver and skeletal muscle.

[citation needed] After two or three days of fasting, the liver begins to synthesize ketone bodies from precursors obtained from fatty acid breakdown.

Starvation ensues when the fat reserves are completely exhausted and protein is the only fuel source available to the body.

Thus, after periods of starvation, the loss of body protein affects the function of important organs, and death results, even if there are still fat reserves left.

In ancient Greco-Roman societies, starvation was sometimes used to dispose of guilty upper-class citizens, especially erring female members of patrician families.

In the year 31, Livilla, the niece and daughter-in-law of Tiberius, was discreetly starved to death by her mother for her adulterous relationship with Sejanus and for her complicity in the murder of her own husband, Drusus the Younger.

A son and daughter of Agrippina were also executed by starvation for political reasons; Drusus Caesar, her second son, was put in prison in 33 AD, and starved to death by orders of Tiberius (he managed to stay alive for nine days by chewing the stuffing of his bed); Agrippina's youngest daughter, Julia Livilla, was exiled on an island in 41 by her uncle, Emperor Claudius, and her death by starvation was arranged by the empress Messalina.

Ugolino della Gherardesca, his sons, and other members of his family were immured in the Muda, a tower of Pisa, and starved to death in the thirteenth century.

According to legend they died of starvation a few weeks later, since their brother had thrown the prison key in the castle moat.

In Cornwall in the UK in 1671, John Trehenban from St Columb Major was condemned to be starved to death in a cage at Castle An Dinas for the murder of two girls.

The Makah, a Native American tribe inhabiting the Pacific Northwest near the modern border of Canada and the United States, practiced death by starvation as a punishment for slaves.