Related Experiment Video
Updated: Mar 22, 2026
08:06
Assessment of the Metabolic Effects of Isocaloric 2:1 Intermittent Fasting in Mice
Published on: November 27, 2019
9.7K
Integrative Physiology of Fasting.
Stephen M Secor1, Hannah V Carey2
1Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, USA.
Comprehensive Physiology
|April 12, 2016
Summary
Animals survive long fasts by reducing metabolism and using stored fat. Hormonal changes and tissue adaptations, including gut microbiota shifts, are key to maintaining homeostasis and enhancing survival during fasting periods.
Area of Science:
- Comparative physiology
- Animal ecology
- Metabolic regulation
Background:
- Extended fasting is common in nature, impacting reproduction, development, and survival.
- Organisms must maintain homeostasis using only internal resources during fasting.
- Survival depends on integrated behavioral, physiological, and biochemical adaptations.
Purpose of the Study:
- To review the integrated physiological, morphological, and biochemical responses during natural fasting bouts.
- To elucidate the mechanisms animals use to survive extended fasting periods.
- To understand the hormonal and immunological alterations during fasting.
Main Methods:
- Literature review synthesizing existing research on animal fasting.
- Analysis of physiological, morphological, and biochemical adaptations.
- Examination of hormonal regulation, immune function, and tissue responses.
Main Results:
- Fasting survival relies on reduced metabolic rates and increased lipid utilization.
- Hormonal profiles shift, with decreased digestive/metabolic hormones and increased substrate utilization hormones.
- Body mass loss occurs through fat depletion and tissue atrophy, varying by organ usage.
- Gut microbiota composition and function are altered, impacting host physiology.
Conclusions:
- Animals possess a complex suite of adaptations to survive prolonged fasting.
- Fasting survival involves coordinated changes in metabolism, hormones, tissues, and the gut microbiome.
- Gene expression programs are crucial for orchestrating these integrated physiological mechanisms.
More Related Videos
08:30Intraperitoneal Glucose Tolerance Test, Measurement of Lung Function, and Fixation of the Lung to Study the Impact of Obesity and Impaired Metabolism on Pulmonary Outcomes
Published on: March 15, 2018
14.8K
11:03Measurement of Fatty Acid β-Oxidation in a Suspension of Freshly Isolated Mouse Hepatocytes
Published on: September 9, 2021
4.6K
Related Concept Videos
01:24Metabolic States of the Body: Fasting and Starvation
3.3K
During the initial hours of fasting, the body uses up its glycogen stores as an energy source. Once these glycogen reserves are depleted, the body begins breaking down stored triglycerides and structural proteins. During this stage, glycerol becomes a key substrate for gluconeogenesis, while free fatty acids undergo beta-oxidation to provide energy for tissues, such as skeletal muscle. In the fasting state, the body spares protein breakdown as much as possible to conserve muscle and structural...
3.3K
01:18Metabolic States of the Body: The Postabsorptive State
1.6K
The postabsorptive state usually starts about four hours after a meal and lasts until the next meal is eaten. During this time, the digestive system stops absorbing nutrients, and the body uses stored energy reserves to maintain stable blood glucose levels.
Initially, glycogen stored in the liver is broken down to release glucose into the bloodstream, while glycogen in the muscles is broken down to supply glucose for energy directly within the muscle cells. As glycogen stores diminish,...
Initially, glycogen stored in the liver is broken down to release glucose into the bloodstream, while glycogen in the muscles is broken down to supply glucose for energy directly within the muscle cells. As glycogen stores diminish,...
1.6K
01:25Metabolic States of the Body: The Absorptive State
2.0K
During the absorptive state, which lasts approximately four hours after a meal, the body absorbs nutrients from the gastrointestinal tract. The carbohydrates, proteins, and lipids we consume are broken down into monosaccharides, amino acids, and free fatty acids for absorption. While carbohydrates and proteins are absorbed as-is, lipids are absorbed in their broken-down forms and then re-esterified into triglycerides within enterocytes before being packaged into chylomicrons. These absorbed...
2.0K
01:02Glucose Homeostasis: Regulation of Blood Glucose
5.1K
Carbohydrates consumed through foods are converted into glucose, a crucial energy source for the body. In the prandial state, high blood glucose levels stimulate the secretion of insulin from the pancreas. Insulin inhibits hepatic glucose production and stimulates glucose uptake and metabolism by muscle and adipose tissue. The excess glucose is converted into glycogen and stored in the liver and muscles.
During fasting, when blood glucose levels are low, the pancreas secretes glucagon. it...
During fasting, when blood glucose levels are low, the pancreas secretes glucagon. it...
5.1K
01:16Hormones Regulating Blood Glucose
8.3K
Insulin is released by beta cells of the pancreas when blood glucose levels are high. It facilitates glucose absorption and utilization in insulin-dependent cells with insulin receptors on their plasma membranes. Insulin promotes glucose uptake by increasing the number of glucose transport proteins in the cell membrane, allowing glucose to enter the cell. As a result, glucose utilization and ATP production are enhanced.
In addition to accelerating glucose uptake and utilization, insulin has...
In addition to accelerating glucose uptake and utilization, insulin has...
8.3K
01:30Regulation of Food Intake
3.1K
Short-term regulation of food intake primarily involves neural signals from the gastrointestinal (GI) tract, blood nutrient levels, and GI tract hormones. Communication between the gut and brain via vagal nerve fibers plays a significant role in evaluating the contents of the gut. Clinical studies have shown that protein ingestion produces a more prolonged response in these nerve fibers compared to an equivalent amount of glucose. Additionally, the activation of stretch receptors caused by GI...
3.1K