When we talk about the effects of famine on the human body, what we are actually talking about are the effects of starvation on the body. “Famine,” according to the Oxford English Dictionary, is “(e)xtreme and general scarcity of food, in a town, country etc… ”; “starvation,” according to the Oxford Advanced Learner’s Dictionary* is “suffering or death due to hunger.” “Starvation” is the biological consequence of continuous scarcity of food. When we talk about famine, we are ultimately talking about starvation on a mass scale.
The Starved-Fed Cycle
Under normal conditions, the body goes through what’s known as the “starved-fed” cycle, according to J.M. Berg, J.L. Tomoczko, and L. Stryer’s Biochemistry. They write that this cycle has “three stages: the postabsorbative state after a meal, the early fasting during the night, and the refed state after breakfast."
The starved-fed cycle is in large part driven by glucose, and alterations to the cycle tend to occur in its absence. "A major goal of the many biochemical alterations in this period is to maintain glucose homeostasis—that is, a constant blood-glucose level” (Berg, Tomoczko, and Stryer). Glucose is a sugar obtainable from carbohydrates, which stimulates the release of insulin, a key player in the body’s internal regulation. Insulin stimulates the creation of proteins and the storage of glucose within the body as glycogen. Insulin tells the body when it is “fed”. Later, the blood-glucose level lowers, which in turn causes insulin production to decrease in favor of glucagon, which is the other major regulator of fuel metabolism. “Just as insulin signals the fed state, glucagon signals the starved state,” write Berg, Tomoczko, and Stryer. In lieu of incoming glucose from carbohydrates, glucagon stimulates the release of glucose from previously-stored glycogen. When another meal is eaten, incoming carbohydrate-derived glucose is used to replenish the body’s store of glycogen, beyond which point the normal starved-fed cycle begins anew.
The Body in Starvation
During starvation, the body still prioritizes maintenance of the blood-glucose level. However, certain parts of the body which rely on glucose more than others (e.g. the brain) are prioritized. The muscles switch to fatty acids as fuel. The liver begins transforming several different compounds into glucose in order to compensate for the lack of carbohydrate-derived glucose from food intake. One of these materials for glucose production is glycerol, derived from stored triacylglycerol, which is a primary component of body fat. As starvation progresses, more and more of the brain’s fuel is provided by ketone bodies rather than glucose. (Ketone bodies are water-soluble molecules created by the liver during the process of synthesizing glucose.) These shifts in fuel sources serve to stymie muscle loss during starvation. Death from starvation happens after the body’s store of triacylglycerol is gone and protein degradation is then allowed to occur leading eventually to organ failure.
“A person’s survival time is mainly determined by the size of the triacylglycerol deposit.” (Berg, Tomoczko, and Stryer)
*The OED’s definition of starvation as “the action of starving or subjecting to famine” is unsatisfactory.
Interactive Diagram Below
Hover over the diagram to learn more about the effects of starvation on different parts of the body
Each of the points represents a separate phase of starvation:
Green is phase one
Blue is phase two
Red is phase three
“famine, n.” OED Online. Oxford University Press, December 2015. Web. 28 February 2016.
“Section 30.3 Food Intake and Starvation Induce Metabolic Changes.” Berg, J.M., J.L Tomoczko, and L. Stryer. Biochemistry, 5th ed. New York: W.H. Freeman, 2002.
“starvation.” Oxford Dictionaries. Oxford University Press. Web. 28 February 2016.
"starvation, n." OED Online. Oxford University Press, December 2015. Web. 28 February 2016.