As I've entered my 30s I've observed many of my peers who held this mentality already experiencing some decline from their unhealthy lifestyles. They make old man noises as they stand up and sit down, they can't stand for more than a few minutes, and a short walk leaves them visibly tired.

You don't have to decline in your 30s like that. Your body was made to move. Humans literally evolved to hunt animals by simply chasing them until the animal collapses from exhaustion. With a little bit of effort you can get that kind of stamina. Start taking walks regularly, maybe even run a little. Drink less soda and alcohol, reduce your sugar intake.

I spent the first half of my 20s a decaying lump that used the computer all day at work then drove home to use the computer all night at home, eating half a bag of candy in one sitting (aka about a dozen servings or more) then during the pandemic a coworker turned me on to a home workout routine that was appropriately communicated so even as a nerd who struggled to lift 40 lbs I could understand it. Working out regularly led me to improving my diet as my body started asking for better food. I lost the fitness habit when I went back to college, but I had already gotten to where I could manage my first pull-up ever in my late 20s (I'd literally never been able to manage a single pullup before) then two years ago I climbed into my bike for the first time in a decade with the goal of being able to do my kids school pickups and dropoffs by bike. I quickly found how out of shape I was and started biking every day. At first it was only 5-10 minutes a day because I could only manage one lap around the block, but slowly I got better. Soon I could go half a mile, a mile, 2 miles, 4 miles and finished the season almost able to bike 10 miles in a ride. This year I hit my next milestone of biking to the next town over and back (about a 22 mile round trip) and started doing school pickups and dropoffs by bike (and I'm literally the only parent doing so at my kids school!) oh and I still use the computer a lot but I've also started picking up other hobbies because I realized I don't want to spend my entire life staring at screens. I picked up and lost a drawing habit, I've been reading a lot more and recently I've started picking model railroading back up as a hobby. I'm literally in the best shape of my life and feeling good. And I only make old man noises some of the time when sitting on the floor!

The point is, it is absolutely worth it to pick up some healthy habits and drop some unhealthy ones. The physical and psychological benefits are totally worth it. My whole body feels so much better to live in. Just start small. Maybe take a walk every day (seriously more people need to take walks around their neighborhoods, you'll feel so much more connected with your community!) reducing/dropping soda and alcohol is also life changing. I know a couple of people who lost a ton of weight just by dropping soda and making no other dietary changes. You don't realize how bad soda is until you take your first sip of soda in years and go "omg that's way too much sugar how does anyone drink this?" Your body wasn't evolved to drink litres of sugar-coated carbs and sit in chairs all day, and you're not going to have a good time if that's what you do. Making some small lifestyle tweaks can be completely life-changing and all for the better at that