While fasting, the body experiences several changes. It starts becoming weak, blood pressures tends to drop, and there are some signs of skin eruption, headaches, nausea and diarrhea due to metabolic process that begins to rise in the body. Metabolic changes occur due to the conservation of protein of the muscle through the decrease of muscle protein turnover.
The first process that occur during prolonged fasting is the process in which the adipose tissues breakdown its triacylglycerol stores that provide glycerol and fatty acids to the blood. The fatty acids produced acts as a major fuel source to the body. The glycerol is changed to glucose, whereas the fatty acids are oxidized to form water and carbon dioxide by tissues such as muscles (Henning, pp. 199-214).
Muscles gradually reduce the consumption of ketone bodies produced from the fatty acids for its fuel. Ketone bodies are chemical compounds that the liver produces from fatty acids when there is low-food intake for the body cells to use it as energy instead of glucose. As a result, the ketone bodies’ concentration rises in the blood. The brain starts to consume these ketone bodies from the blood and then oxidizes them for energy. Consequently, the brain requires little glucose than usual after an overnight fast. The brain maintains the use of the little amount of glucose that oxidizes for energy and uses it as a source of carbon for the neurotransmitter synthesis. Overall, the body uses a little amount of glucose and; therefore, the liver produces less glucose per hour during the period of prolonged fasting than during shorter fasting periods (Alberts et al., pp. 65-79).
Signs and Symptoms of Starvation
Starvation is a metabolic response experienced when the body lacks food. The first sign of this condition is stomach pain that begins within three to five days of fasting. Severe constipation occurs as there is no bowel movement due to lack of food. When people do not eat at all for some time, they experience fatigue, and their eyes appear sunken. The body temperature decreases and lastly the hands and feet swell showing symptoms of starvation (Keys, pp. 288-291).
Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. New York: Garland Science, 2002:65-79. Print.
Henning, S.J. Gastrointestinal and liver physiology. American Journal of Physiology 241, 199- 214, 2010. Print.
Keys, A. Pioneers recollections in nutrition: from starvation to cholesterol. Journal of Nutrition 9: 288–291, 1998. Print.