Hunger strike - International guidelines and medical management
Schematically, the following physiological events occur during total fasting (absorption of water only: around 1.5 - 3 l/day):
- Glycogen stored in the liver and in muscular tissue is the source of energy during the first few days of total fasting. Glycogen reserves are used up after 10 – 14 days. It is then that amino acids are called up to provide glucose through gluconeogenesis.
- The gluconeogenesis process leads to the massive breakdown of protein, i.e., muscle tissue, including the heart muscle.
- Fatty acids coming from the breakdown of fat tissue (lipids) are broken down into ketones, which also provide energy. This phase begins early on in the fasting, and the ketosis suppresses hunger pangs after 2 – 3 days.
- Protein is catabolized but is spared by the body, providing only 10% of the energy source. Once all lipid reserves are used up, what remains of muscle tissue is tapped. This theoretically leads to a catastrophic situation, but other complications usually appear before this.
- Significant weight loss occurs at the very beginning of total fasting, mainly from glucagon-induced loss of fluid (natriuresis) [ 8 ] .
- Medical monitoring is generally recommended after 10% weight loss in non-stout individuals, or once a Body Mass Index of 16.5 is reached [ 9 ] .
- Major problems arise roughly when weight loss is around 18 % – 20 % of the initial weight.
 See Kalk, WJ, Felix M, Snoey ER, Veriawa Y. Voluntary total fasting in political prisoners – clinical and biochemical observations. S Afr Med J 1993; 83
 The Body Mass Index (BMI) of an individual is body weight in kilos over the square of the height in meters. BMI values are independent of physical constitution or ethnic build. Over 20 corresponds to well-nourished. Under 16 for men (15.5 for women) corresponds to malnutrition.