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How does the liver store glucose as glycogen and release energy from fats?

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USDA MyPlate dietary guidelines — human nutrition MyPlate, a revised set of dietary guidelines introduced by the U.S. Department of Agriculture (USDA) in 2011, divides the four basic food groups (fruits, grains, protein, and vegetables) into sections on a plate, the size of each section representing the relative dietary proportions of each food group. The small blue circle shown at the upper right illustrates the inclusion and recommended proportion of dairy products in the diet.

The liver plays a central role in energy homeostasis by managing the storage and mobilization of nutrients based on the body's metabolic state.

Glucose Storage and Mobilization

In the "fed" state, elevated blood glucose levels trigger the release of insulin from the pancreas. Insulin stimulates the liver to take up glucose from the blood and store it as glycogen, a process that helps lower blood sugar levels.1

When blood glucose levels drop—such as during fasting—insulin secretion decreases and the pancreas releases glucagon. This hormone stimulates glycogenolysis, the process by which the liver breaks down stored glycogen into glucose. This glucose is then released into the bloodstream to maintain energy levels for the brain and other tissues.12

Energy Release from Fats

When glucose and glycogen stores are depleted, the liver mobilizes energy from fats. It converts stored fatty acids into acetylcoenzyme A (acetyl CoA), an energy-releasing form. During prolonged fasting or starvation, the liver further converts these fatty acids into ketone bodies, which serve as an alternative fuel source for the brain. Additionally, the liver can synthesize storage fats (triglycerides) when nutrient intake exceeds the body's immediate energy requirements.31