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Which Organ Uses the Most Energy?

Human BodyBiology

Quick Answer

The brain uses the most energy relative to its size, consuming about 20% of the body total energy despite being only 2% of body weight.

The Full Story

The human brain weighs about 1.4 kg — roughly 2% of total body mass — yet it consumes approximately 20% of the body resting energy, using about 20 watts of power (equivalent to a dim light bulb). Most of this energy goes to firing neurons and maintaining the electrochemical gradients needed for nerve signalling. The brain has almost no energy reserves and depends on a continuous supply of glucose and oxygen delivered by about 600 ml of blood per minute. If blood flow is interrupted for just 5-10 seconds, consciousness is lost.

Key Facts

1.Neurons consume about 75% of the brain energy budget; the rest goes to supporting glial cells.
2.The brain uses about 120 grams of glucose per day — roughly 6 times the amount used by skeletal muscles at rest.
3.During intense mental effort, overall brain energy use rises only about 5%, because most energy goes to baseline maintenance.

YouTube Angle

Suggested video title for this topic:

"Your Brain — The Hungriest Organ in Your Body"