Ok, so this is going to sound really, really mean but I was 31 and living away from home when Facebook took off and I was slightly later joining it than most people I knew. In the first month or so, I connected with loads of old friends who I hadn't seen much in the previous 7/8 years. The women all looked largely the same. Yes, most of us had put on a little weight but by and large there wasn't much different between their very early 30s selves and their early-mid 20s selves.
However the majority of the men looked honestly, really awful. Paunchy, bloated, red faced, receding hairlines that aren't bad in and of themselves but are when still cut in a way that needs a full head of hair. Badly dressed, even sometimes in expensive branded clothes but ones that no longer suited them or fit properly. About 20-30% of men who hadn't let themselves go looked great and it was clear from their facebook that they were either making an effort to stay physically in shape, often posting about their runs/cycles/football training/etc and/or had a physical job.
With very little effort the women had stayed the same. Even with extra weight, they didn't look so utterly aged. The men who similarly 'let themselves go' really, really looked it.
I spent a lot of my late 20s and 30s overweight and was on the cusp of obesity at 39. That was ageing, as in I didn't look super old, but I looked dowdy and the natural fullness of my eyes and lips were hidden and my cheekbones no longer stood out. I'm small with an hourglass figure but was starting to become rounded and shapeless. More than that, I had less energy and playfulness. I didn't look as bad as many of the men I knew did, but if you don't take care of your body, it does eventually take it's toll on your looks and more importantly your abilities. At 39, I decided to lose the weight, at 40 I accidentally found my 'sport' by 41 I was athletically fit with excellent ultra-endurance. I'm 42 now and despite a bout of what was most likely "long Covid" I'm back in shape, strong, muscular, increasingly flexible and just constantly full of reserves of energy and just utter joy brought on by my physicality. I look younger than I have done in a long time (though obviously up close you can see the lines on my face and a crap night's sleep shows up in ways it didn't 20 years ago).
What I have found though, is that it's pretty rare for women my age to still be fit/re-find fitness. Whereas the men who were keeping in shape at 30, are still doing so at 40. I think that's down to 2 things. Men are more likely to insist on pursuing their hobbies even with kids, while women have less time for themselves. And the absolute fucking lie we are told about accepting our post-pregnancy bodies. What was once a good message about not beating ourselves up about how pregnancy can change us, has morphed into a learned helplessness that stops us from even trying to change all the things that we do have power over. I've been utterly fucking amazed at how the belly I spent years 'accepting' has morphed into something I'd proudly display to the world if I didn't think it would make me look vain.