Meditative concentration (dhyāna-samādhi) can reduce the consumption of the energy of the four great elements

When there is meditative concentration (samādhi), one needs less sleep, and the body does not require too much sleep. This is because meditative concentration itself can reduce the activity of the six consciousnesses and lessen the consumption of the four great elements' nourishment. Meditative concentration can also reduce the manas' grasping and engagement, decrease the activity of the physical body, and reduce its pulling on and control of the body's entire nervous system. The brain's nervous system, the five internal organs and six viscera, and the whole body can then be less active and consume less of the four great elements, so the body does not become fatigued, and the manas does not need to decide on sleep.

The deeper the meditative concentration, the less sleep is needed—so much so that one can completely stop sleeping. Because at this point the manas is very quiet, no longer intending any activity or fabrication, it no longer excessively mobilizes the brain's nervous system; there is very little activity of the body faculty and very little activity of the conscious mind. The more concentrated the manas is, the less it grasps and engages, the less regulatory activity there is, the less of the four great elements is consumed, and the less sleep and food are needed.

Some people, in their daily work, do a great deal of work yet have very few mental thoughts; their consumption is low, so they do not need to eat so much food or have so much sleep, and yet they remain full of energy. This shows that what consumes the energy of the four great elements the most is the mental activity of the manas, while the six consciousnesses themselves do not consume very much. Therefore, even though the workload of the six consciousnesses is not reduced in the slightest, when the manas has fewer mental thoughts, the amount of activity decreases, and the work no longer feels tiring.

From this we can see that the manas can grasp and understand the condition of the physical body anytime and anywhere, and can regulate and direct it anytime and anywhere. He discerns with great agility and subtlety—not coarsely at all. It is not that the mind consciousness is unaware of the body's various conditions and needs the manas to hint and alert it.