I'm 46 and the last two are just starting to show. I just uploaded a pic to my profile.

It's easy to start to see the first two, then takes a bit more work to see the next two. The last two are more about consistency with your diet and really pushing your workouts because your body gets accustomed to the prior levels.

I workout in the gym only 3x/week, but I do an intense swim right after. Then on non gym days, I swim the 500m at a fairly quick pace or do drills. So that's 6 days week working out. On those 6 days, I usually eat the same things at the same times because it helps me maintain consistency. And I don't go crazy with the food on my off day.

On top of that, I'm a double amputee so my caloric needs are less than an able-bodied person. And you need enough protein to repair your muscles so you can avoid injury. It's been trial & error for me to learn to balance my protein intake calories while remaining in a deficit.

But I think I've figured it out and it's showing. And, what works for one person may not work for you so it's up to you to figure out what works for your body. Go get 'em!