Do you find yourself bending down to tie your shoes and wonder, “What else can I do while I’m down here?” When you have a party, do your neighbors not even notice…because it ends at 8:30 p.m.? Do you have a favorite burner on the stove and you get mad when somebody else uses it? Well, these could be signs that you are getting older.

While you probably knew you might age eventually, more and more scientific studies are showing that your chronological age and your biological age might not be the same. How can that be, you ask? Isn’t your effective age determined by the number of your birthdays? It turns out—not necessarily.

Recently, I came across an article entitled, “How Old is Your Body? Stand on One Leg and Find Out.” It didn’t tell me how old my body is. But now I suspect that flamingos are immortal.

The article examines a 2024 issue of The Public Library of Science Computational Biology. The theme of the issue is that individuals and even different organs within individuals can age at different rates. For example, a smoker’s lungs might appear to be older than the rest of his body. A person who walks every day might have the heart of a much younger person. And your body is not an hourglass that runs out of sand at a constant, linear rate. There are clumps in your sand—exercise, healthy diet etc. that slow down the process. And some of your sand may be finer and runs out more quickly.

Wrinkles, gray hair and forgetfulness are obvious signs of…um (what was I saying?) But there are also less apparent signs that correlate with biological age. Prominent among them is balance. Roughly speaking, according to the article, the longer you can balance on one foot, the lower your biological age.

(Be honest, you’re standing on one foot right now.) This sounds like one of those pranks. Stand on one foot. Now close your eyes and hold your arms out straight. Now touch your nose. Now recite the alphabet backwards. Eventually, you realize everybody around you is trying not to laugh out loud. I would say my balance is fairly normal. But my feet are so big and square, I could sleep standing on one foot. And, of course, as the author points out, you can get better at standing on one foot with practice which renders the test pretty much useless.

A Stanford Medicine study reports that biological aging is far from constant. “Rather,” it says, “we undergo two periods of rapid change during our life span, averaging around age 44 and age 60.” So there you are, at 43, looking and feeling younger than your actual years and BAM–your molecules take a dive and you suddenly catch up to your real age. It can be quite a shock.

Yale Medicine Magazine notes that, by 2034, for the first time in history, the population of Americans over 65 will outnumber that of Americans under the age of 18, producing what they refer to a “tsunami of health care needs”.

There are a number of companies springing up, eager to tell you your biological age—for a price. But the Yale study encourages people while they are still younger than 44 or 60 and still healthy, to adopt a healthier lifestyle before it’s too late. Stop smoking, exercise, cut back on alcohol, get more sleep. And don’t bother standing on one foot. It won’t help.