After my wife and I had our first kid a few years ago, I joked that becoming a father was a great way to get out of shape. There are two main reasons for this: 1) most of your free time is gone, so it’s much harder to get to the gym or wherever else you normally get exercise; and 2) you’re getting a lot less sleep at night, which means that you’re more likely to eat like a pig during the day.

I’m not exactly tipping the scales these days, but as I get deeper and deeper into my 30s, staying in shape is becoming noticeably harder. In terms of diet, I probably eat better now than I ever have. I’m far from perfect, but I’m down to about one sugary drink per week, I hardly ever have anything with white flour, and I try not to snack after dinner. And yet, the dress pants that I had the dry cleaner take out for me just a few months ago are once again feeling snug around the waist.

Of course, there’s another reason besides less exercise and less sleep that explains why men struggle to stay in shape as they get older: declining testosterone. Scientists have long understood that testosterone levels gradually fall as men get older. A 2011 study, however, added one more remarkable finding: becoming a father is associated with an even steeper decline.

If you’re a dad and you just felt a subtle sensation of depression wash over you as you read that, you’re not alone. Testosterone is, to many of us, what defines us as men. It helps us build muscle and stay lean, makes us more attractive to women, and keeps us interested in sex. It’s also what gives us an appetite for taking risks and being aggressive. Basically it makes us more like Chuck Norris.

Now, there just so happens to be a whole industry built on the premise that men should intervene to prevent this natural decline in testosterone as they age. If you’ve been watched anything on TV that middle aged fat guys tend to watch (NFL football is a good place to start), then you may already be familiar with the concept. A few years ago the pharmaceutical company Abbvie, maker of the testosterone replacement therapy drug Androgel, went all out with a marketing campaign that asked men the question: “Is it low T?” The apparent idea was to implant in the minds of aging men whose bodies were getting flabbier, sex drives duller, and energy levels lower that these changes were being driven by a deficiency of testosterone. These campaigns worked; increasingly, doctors prescribed testosterone therapy to all sorts of men, some of whom no doubt were experiencing perfectly normal declines in the hormone associated with age. Sales of testosterone therapy treatments jumped 65% between 2009 and 2013, according to the Food and Drug Administration.

Quite sensibly, in 2014 the FDA cracked down on these companies, ruling that the drugs couldn’t be marketed for anything except abnormally low testosterone levels — an actual clinical condition called hypogonadism — and not just the normal effect of aging. Try going to isitlowt.com these days and you’ll be redirected to Abbvie’s much less catchy new website, isithypogonanadism.com. Doesn’t have quite the same ring to it.

But even as prescription testosterone is now more heavily regulated, its spirit is very much alive. Recently at work, where the TV on my corner of the trading floor is regrettably locked to CNBC, I’ve been seeing a lot of ads for Cenegenics, an anti-aging company for men. The symbol of the company to this point has been the shirtless image of its founder, Jeffry Life, an old guy with inexplicably ripped muscles. “See how your next years can be your best”, runs a tag line on the Cenegenics website, which also features a picture of a grey-haired guy in sunglasses riding in a convertible with a hot young woman in the passenger seat.

There’s nothing wrong with people wanting to feel younger and more alive, of course. The issue, however, is the notion that the natural changes that we all experience as we get older are somehow shameful, or even need to be treated as a disease. Women have been dealing with this for decades, if not longer; just think about all the anti-wrinkle creams, hair dyes, and push-up bras out there on the market, enticing women to “defy” their age. Increasingly, clever advertisers are finding out they can tap into the same insecurities in men.

Of course, “defying” one’s age is never without cost. The specific problem with men artificially keeping their testosterone levels elevated as they age is that it may have serious health consequences down the line. There’s some evidence that higher testosterone may be bad for heart health, for instance, even as it might make us more energetic and vibrant.

But never mind that for a moment. Let’s acknowledge the behavioral aspects of testosterone. Maybe getting calmer and less aggressive as we age and become caregivers to our kids isn’t such a bad thing. The whole evolutionary biology element of this makes a great deal of sense; whereas in our younger years nature tells us to take risks, compete, and find a mate, as we pass beyond that stage it tells us to take care of our woman and guard the family. Our physical reality changes, and thus so do our hormones. In the words of evolutionary biologist Richard J. Wassersug, imagining a prehistoric context: “The argument can be made that it’s not beneficial to have the mindset of a 19-year-old when you are 49-years-old, because if you are aggressive enough to get into a conflict with an actual 19-year-old, you are going to get killed.”

There’s a definite spiritual component to all of this, in the sense that spirituality and religion at their core are about letting go of desire and accepting reality as it is, not how we want it to be. They’re about being able to discern between the eternal and the ephemeral. The best passage from the Baha’i Writings I could find that relates to this subject is this one, from a talk by Abdu’l-Baha:

All bodies are disintegrated in the end; only reality subsists. All physical perfections come to an end; but the divine virtues are infinite. How many kings have flourished in luxury and in a brief moment all has disappeared! Their glory and their honor are forgotten. Where are all these sovereigns now? But those who have been servants of the divine beauty are never forgotten. The result of their works is everywhere visible.

Let me be clear that I have no interest in my body “disintegrating”, at least not while I’m living. I want to stay in shape. I want to be able to play some pick up basketball on the weekends without passing out from exhaustion. I want my wife to consider me physically irresistible, not just a good dad or a good husband. There’s nothing wrong with any of these things, of course. But at the same time, I need to recognize where I am in life and what my duties are at this stage. None of us lives for ever, and none of us is young forever, either. That’s the way it should be, after all, so that we can watch our sons and daughters grow up and take control of this world and, hopefully, succeed in ways we never could in our own heyday. Recognizing that isn’t just about accepting reality; its about embracing it, and gaining the peace of mind that comes with understanding life’s deeper purpose.