I'm about to be 49, and the only way I've lost weight since I turned 40 has been to count calories and to exercise. In 2020 I put on 20lbs. In 2021, I lost 25lbs in about 3.5 months. I wasn't looking to work out a shit ton, so most of my exercise was walking and elliptical. Otherwise, it was diet, i.e., a caloric deficit of about 400 calories a day.
But by this summer I'd gained back a lot of the weight I'd lost (I was at 264lbs and I'm only 6 foot) so I'm back at it. I'm down 8.5 lbs in a month...counting calories and exercising. I finally got a membership to a local pool and I'm doing laps again. When I was doing laps twice a week back in 2008-2010, I was in the best shape I'd been in since college. I highly recommend swimming for 40+ yr olds b/c of the low impact. It's also a hell of a lot more fun than running. I find it easy to burn 500 calories and there's something calming about it.
That's just my experience, fwiw. I will say it gets harder as you get older, that's the main thing I've learned. I saw Springsteen in 2016 (having seen him many times prior) and finally noticed that he was getting old. But the only reason I noticed it was because his body language was very laid back to start the show. Why? Because he played a 3.5 hour show. At 67 years old. How? Because he's in excellent shape. He can afford all the trainers in the world, sure, but I have no doubt he puts more time into his physical health now than he did even when he bulked up around the time of Born in the USA.