Sorry, How Old Are Katy Perry And Justin Trudeau?

Last week, Katy Perry posted a carousel of photos and asked her more than 200 million followers the slightly nonsensical question: “How old would you be if you didn’t know how old you were?”

The caption referenced an image of the “Teenage Dream” singer and her beau, former prime minister Justin Trudeau. In the candlelit snap, the duo—who have been romantically linked since last summer—are each shown smiling and holding up their mobile phone screens to display their “biological ages.”

Perry, who is 41, is rated as being 33 years old, and Trudeau, who is 54, is given the age score of 43.  

Lauren Sanchez Bezos, Amazon honcho Jeff Bezo’s wife and Perry’s space-mate in the much maligned Blue Origin space flight, was one of the pop star's many followers who hearted the carousel.

What is biological age—and what does it *really* indicate?

Biological age is different from a person’s chronological age. Instead of counting the years since you were born, biological age estimates how you’re aging by assessing the health of your tissues and organs.

Both Perry and Trudeau reportedly got their biological age results from a company called Function Health, which responded to Perry’s post with a orange heart and “act your biological age” message. (It’s not clear if the twosome underwent the lab testing Function offers, but it’s hard to imagine how they got their results if they didn‘t. It's also unclear as to whether either has a partnership with the company; none was disclosed in Perry’s post.)

To discover your biological age, you need to undergo multiple blood and lab tests—some health data companies like Function even include MRIs and CT scans as optional add-on services. The Function Health site lists 160 lab tests used to determine biological age; an annual membership—which includes two rounds of testing—is US$365.

While direct-to-consumer biological age testing is beloved by wellness-centric celebrities and influencers—the Season 5 finale of The Kardashians featured at-home biological age testing—there isn‘t a lot of science to suggest these tests are accurate or meaningful.

On the bright side, there is a lot of cheap and cheerful advice aimed at aging well and preventing chronic illness out there. And while eating a diet rich in fruits and vegetables, whole grains and lean proteins, avoiding smoking and getting the recommended amount of daily exercise, for example, likely won’t you win any social follows or sponcon deals, it’s free for the taking.

In related news, here's why Justin Trudeau, Prince Harry and Olympic gold medallist Eileen Gu were spotted together recently.