{"id":7619,"date":"2025-08-29T00:02:52","date_gmt":"2025-08-28T20:32:52","guid":{"rendered":"https:\/\/afachemi.com\/?p=7619"},"modified":"2025-12-09T00:04:01","modified_gmt":"2025-12-08T20:34:01","slug":"what-happens-during-prolonged-starvation","status":"publish","type":"post","link":"https:\/\/afachemi.com\/en\/what-happens-during-prolonged-starvation\/","title":{"rendered":"What happens during prolonged starvation?"},"content":{"rendered":"
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Fed State continues after the last meal until all the food eaten is absorbed, and then the body uses stored fuel if it does not eat. The state that occurs after not eating for a period of one night (from night to morning) is called post-absorptive style or basal state.<\/span><\/p>\n

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In this case, the decrease in the amount of insulin in the blood causes the released fatty acids to move between internal organs and be oxidized, while pure glucose is produced from liver glycogen and amino acids are released from the muscles.<\/span><\/p>\n

The body’s dominant fuel in the post-absorptive state, or the stage after the food eaten has been completely absorbed, is fat, even when a person has a diet rich in carbohydrates. Studies have shown that two-thirds of the body’s resting energy content (REE) in the post-absorptive state comes from fat.<\/span><\/p>\n

At this time, 8 to 10 grams of glucose enter the body’s tissues from the bloodstream every hour. Normally, glucose is the main fuel for brain cells, and a decrease in blood glucose levels below a critical level causes a decrease in consciousness and its continuation causes the death of brain cells. For this reason, there is no room for error in regulating blood glucose levels. Therefore, there is always a complex mechanism to maintain blood sugar levels, which is often controlled by the secretion of two hormones: insulin and glucagon. In the stage after the absorption of ingested food, the continuous absorption of glucose from the bloodstream by body tissues causes a decrease in blood sugar levels and, in parallel, insulin in the blood, due to which the rate of sugar uptake from the blood by muscle and fat cells decreases, and at the same time, glucose production in the liver (glycogenolysis) is stimulated and glycogen production from glucose in the liver is inhibited, and therefore glucose is continuously released from the liver into the bloodstream.<\/span><\/p>\n

Glucose production from amino acids, lactate, and glycerol continues even after a meal (when food is absorbed into the bloodstream). Even after food is absorbed, approximately half of the blood sugar comes from glucose production in the liver.<\/span><\/p>\n

In fact, the contribution that hepatic gluconeogenesis makes to the supply of glucose in the bloodstream is directly related to the amount of carbohydrates and protein in the food eaten (at the last meal), because these factors determine the amount of liver glycogen stored. Now, as the fasting period becomes longer, the glucose molecules produced by the gluconeogenesis process are released into the blood, instead of being stored in the liver and leading to the production of hepatic glycogen, and thus the liver gradually releases all its glycogen stores into the bloodstream.<\/span><\/p>\n

Fasting longer than 12 to 24 hours reduces blood insulin levels to a greater extent, which causes the metabolism of free fatty acids and glycerol from adipose tissue on the one hand and triglycerides and amino acids from muscles on the other.<\/span><\/p>\n

The transport of these metabolites to the visceral organs provides energy and raw materials for protein synthesis and liver gluconeogenesis. On the other hand, the level of the hormone glucagon in the blood remains constant or increases. (Glucagon is a hormone that converts liver glycogen to glucose.)<\/span><\/p>\n

When the insulin to glucagon ratio in the blood decreases, it stimulates the liver to oxidize more of the acids that have been transported to the liver from adipose tissue and muscle.<\/span><\/p>\n

At this time, as the production of glucose and metabolites that produce acetyl-coenzyme A decreases, the amount of acetyl-coenzyme A produced from the oxidation of fatty acids increases. (Acetyl-coenzyme A is the input for the energy production of the liver’s Krebs cycle.) Part of this acetyl-coenzyme A produced in the liver from the oxidation of fatty acids is converted to carbon dioxide in the Krebs cycle, and this is the dominant energy source, but the largest amount of acetyl-coenzyme A is converted to acetoacetic acid, hydroxybutyric acid, and acetone, which are three molecules called ketone bodies.<\/span><\/p>\n

If fasting continues for more than 2 to 3 days, it will deplete almost all of the 80 grams of liver glycogen stores and half of the muscle tissue glycogen stores.<\/span><\/p>\n

When all liver glycogen stores are depleted, all glucose that is oxidized in the body is produced through gluconeogenesis from two classes of glucose precursors, namely:<\/span><\/p>\n

1 \u2013 Glycerol and glucogenic amino acids (glucose producers)<\/span><\/p>\n

2- Lactate and pyruvate (three-carbon intermediates that are the result of glucose breakdown and under these conditions enter the glucose synthesis cycle.)<\/span><\/p>\n

On the other hand, as blood glucose levels decrease, the uptake of glucose from the blood by the body’s cells also decreases, and on the other hand, the brain switches to using ketone bodies instead of glucose as its main fuel, and this happens approximately after 3.5 to 4 days of fasting.<\/span><\/p>\n

Ketogenesis (i.e., ketone body production) is the main symptom of prolonged fasting. Under normal nutritional conditions, only 2-3% of the resting energy requirement (REE) is provided by ketone bodies, and when the level of ketone bodies reaches a measurable level in the blood, it approximately indicates 2-3 days of fasting. Therefore, in short-term fasting of about 10-12 hours, the level of ketone bodies is almost unmeasurable, and only very thin people, and often thin women, have some ketones in their urine, which indicates low insulin levels in the person.<\/span><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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Fed State continues after the last meal until all the food eaten is absorbed, and then the body uses stored fuel if it does not eat. The state that occurs after not eating for a period of one night (from night to morning) is called post-absorptive style or basal state. In this case, the decrease […]<\/p>\n","protected":false},"author":9,"featured_media":7617,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[49],"tags":[],"class_list":["post-7619","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medical-pharma-en"],"_links":{"self":[{"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/posts\/7619","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/comments?post=7619"}],"version-history":[{"count":1,"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/posts\/7619\/revisions"}],"predecessor-version":[{"id":7620,"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/posts\/7619\/revisions\/7620"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/media\/7617"}],"wp:attachment":[{"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/media?parent=7619"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/categories?post=7619"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/afachemi.com\/en\/wp-json\/wp\/v2\/tags?post=7619"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}