Just when you thought you'd heard of every new well-being trend under the sun, along comes another one - quite literally about being under the sun.

Well, one part of your body, anyway - your butt.

Social media is ablaze with the phenomenon of butthole sunning after a wellness Instagrammer named Metaphysical Meagan waxed lyrical on the benefits of exposing your private regions to the energising rays of the sun.

But it wasn't just words that got the online world talking, it was a picture of Metaphysical Meagan in the act - carefully edited not to violate the rules of Instagram, of course.

The Californian woman can be seen lying stark naked with her legs in the air, lifting her behind to the sun.

Metaphysical Meagan illustrates the practice of perineum sunning. Credit: Instagram/Metaphysical Meagan

“I have been practising this for a few months now," she writes on the post.

"I start my day with 5 minutes of perineum sunning & feel energized for hours.

“I no longer rely on coffee for energy to start my day because I am getting my energy from the sun.

Chevron Right Icon 'I no longer rely on coffee for energy to start my day.'

"I also am experiencing better sleep and require less sleep due to boost of overall energy.”

She said it also helped with improving sexual energy and increases one's "personal magnetism."

Famous fan

Metaphysical Meagan is not the first wellness enthusiast to spruik the joys of butthole sunning.

Remember Jackass? Its chief protagonist, Johnny Knoxville, is also a fan.

He re-posted a video from advocate Ra of Earth, who claims that 30 seconds of sunlight on your butt will give you "more energy than in an entire day being outside with your clothes on”.

Meagan claims butthole sunning, or perineum sunning, is an ancient Taoist practice originating in the far East.

“In Taoism, the perineum or Hui Yin is called the 'Gate of Life and Death'," she writes.

"This is a gateway where energy enters and exits the body."

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Metaphysical Meagan points out that the practice is not about getting a tanned butt.

"Sunscreen is not required & all you really need is 30 seconds of sun exposure," she writes.

"The ideal hours of the day to do this are between 7-9 am."

Mixed response

The post has attracted more than 1000 comments, with a mixture of responses.

"What do you recommend to people who don't get any sunshine on a typical dark British day?," one skeptic wrote.

"Ludicrous behaviour. Get a life, then a job, and buy some bloody clothes, woman."

Chevron Right Icon 'Get a life, then a job, and buy some bloody clothes, woman.'

Others were less judgmental.

"New daily office routine?", one person commented, tagging a friend.

"Who knew it could be a solar panel?" wrote another.

Watch in the video below: The rise of the Brazilian butt lift