Every morning, Sandeep S (name changed) was 166.2 cm tall, just over the height requirement for the coveted role of assistant commandant in the Central Armed Police Forces (CAPF).
However, by evening, his height came down to 164.7 cm — mere millimetres shy of the minimum standard.
Having aced the demanding CAPF written exam, Sandeep is now worried he may be rejected for the job due to the height difference.
He posed this question to Dr Sudhir Kumar, a neurologist from Hyderabad, Apollo Hospital, who took to X to discuss the issue and welcomed suggestions from doctors on helping Sandeep.
South First spoke to experts to understand this not-very-known natural physiological phenomenon.
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The phenomenon
Dr Sudhir Kumar said that a lesser-known fact about the human body was its subtle variation in height from morning to evening — a phenomenon that has significant implications for some, like Sandeep.
Imagine waking up every morning slightly taller than you were the night before. This isn’t a fictional scenario but a daily reality for everyone, said the doctor. The variation might be as much as 1.5-2 cm in some cases, he added.
Sudhir explained: “The spine bears the body’s weight as we sit, stand, walk, or run, and this results in minimal compression of the intervertebral discs, resulting in a reduction in height by evening.”
However, Dr Shriram Krishnamoorthy a consultant orthopaedic from Chennai, said: “The general difference I have read of is 0.5 cm, and the highest is 0.78 cm. It is too minuscule to note.”
Sudhir explained: “The Earth’s gravitational forces also play a part in the flattening of the intervertebral discs. On the other hand, as we lie down to relax and sleep at night, the pressure is relieved and the distances between the discs expand. Rehydration of discs also plays a role in the disc size becoming slightly larger at night.”
Krishnamoorthy concurred. He also said: “Walking or moving also creates a slight compression in the cartilage. Considering that we have at least 10-20 joints when standing, each joint experiences a minimum of 2-mm pressure, even with straightforward movement. However, if measurements are taken while a person is lying down, they will typically appear normal.
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Does it occur in all ages?
While the change in height occurs at all ages, it is more pronounced in younger people. This is because the intervertebral discs get dehydrated with ageing, and a variation of disc size between mornings and evenings is lower in older age.
The height between mornings and evenings also varies among genders, and the difference is slightly more among men then women.
Citing a study, certified metabolic health coach and low-carb diet practitioner Shashikant Iyengar said, “There are few studies that say the maximum height loss between 7 am and 7 pm is 2.7 cm, while the mean (average) is 1.61 cm. There is a greater mean height loss in males (1.63 cm) than in females (1.59 cm).”
The objective of the study, by researchers in the Greater Accra Region of Ghana, was to assess the daily height reduction in adults aged 30 years and above. It involved 90 randomly selected participants.
Their height and weight were recorded twice daily, once between 5.30-7.30 am and again between 5-7 pm, using WHO’s stepwise questionnaires for detailed subject information.
The study found that in terms of Body Mass Index (BMI), women showed a larger average difference between morning and evening (1.21 kg/m²) than males (1.02 kg/m²).
A strong correlation was identified between the loss in height and the nature of occupational activities (p-value< 0.001).
It was concluded that there was a notable decrease in participants’ height from 7 am to 7 pm, which then increased from 7 pm to 7 am.
The primary factor influencing these daily height changes was the level of physical activity associated with one’s occupation.
However, the study did not find significant correlations between age, gender, total calorie intake, and the variation in height throughout the day.
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Can it be ‘corrected’?
This height variation is a normal physiological phenomenon, and one need not worry, experts told South First.
However, one might need to maintain a specific height in certain situations. These could be for recruitment for the police, army, navy, or other defence or law-enforcement jobs.
“A person can minimise sitting, standing, walking, or running on those days (when medical check up is due), and spend most of the time lying down. This could minimise the usual reduction in height that is noted as the day progresses,” said Dr Sudhir Kumar.
“It has been noted that Yoga and Pilates sessions on two-three days a week can also help reduce the magnitude of diurnal height loss. Maintaining a good posture while sitting or standing could also help,” added the doctor.
However, Dr Krishnamoorthy said that this was a natural phenomenon and one cannot do anything to correct the height difference that occurs naturally.
