Prakash Kafle / Kathmandu: If our body height is not the same in the morning and evening, there is no need to worry. The fact that human height does not remain constant throughout the day may seem surprising to many, but scientific studies have confirmed that this is a completely natural process. Generally, a healthy adult person is about 1 to 2 centimeters taller in the morning compared to the evening. This change is not due to any disease or problem, but is the result of the interaction between the body’s structure—especially the spine—and the Earth’s gravity force
The human spine is made up of about 33 small bones called vertebrae. Between these bones are soft, flexible, sponge-like structures known as intervertebral discs, a large portion of which is composed of water and fluid. Throughout the day, as we stand, walk, sit, or perform physical activities, the Earth’s gravity force continuously exerts pressure on the spine. This process is known as spinal compression. Due to this pressure, the discs are compressed and the fluid inside them gradually moves out, causing a slight reduction in their thickness. As a result, by the end of the day, a slight decrease in height is observed, and a person appears somewhat shorter in the evening than in the morning. However, this change is not permanent. When we sleep at night, the body remains in a horizontal position, which significantly reduces the vertical gravitational pressure on the spine. During this time, through the process of osmosis, the discs reabsorb fluid from surrounding tissues, a process known as rehydration. After about 8 to 10 hours of rest, these discs return to their original shape and the spine stretches back to its full length. This is why a person’s height is measured to be the greatest immediately after waking up in the morning.
This process becomes even more interesting outside the Earth. In space, where there is no gravity, there is no pressure on the spine, causing astronauts to temporarily grow up to about 2 inches taller. This further confirms that the daily variation in height on Earth is directly related to gravity. On the other hand, as age increases, the ability of intervertebral discs to absorb fluid gradually decreases, which is why a person’s height may permanently reduce slightly in old age.
According to experts, the small difference in height between morning and evening is completely normal and has no negative impact on health. Rather, it reflects the flexibility, adaptability, and dynamic nature of the human body. Therefore, special attention should be given to the time when measuring height—height measured in the morning is considered the most accurate and maximum, whereas in the evening it appears slightly reduced due to the effect of gravity.
