Yes, for me, exercise is critical for both physical & mental health. For the last 15 years, I was overweight & depressed, now I'm back in shape & off my antidepressants as well.
I can only tell you about myself & for me, a lot of exercise works. I have been a competitive swimmer off & on at different times in my life. This year, I'm planning on doing some long distance swims that become the incentive to train. I did a small indoor triathlon in March-I only beat two other women, but I finished & I'm sure I was the only woman over 50 to be competing. I plan on improving next year when I do it. I'm now swimming with some other people who are different levels of swimming. I can remind myself that when I first started swimming after a 10 year absence I could only do 4 lenghths of the pool. It's the same every time I stop working out, I have to start from scratch & that might be 4 lenghths, but this year I plan on doing a six mile swim. I was thinking I'll start walking everywhere instead of using mass transportation just to get the feeling of moving for a few hours a day.
I do think exercise helps a lot, but what exercise & how much has to be a very individual thing. If you're wondering, just start doing something and congratulate yourself. It definitely gets easier & the best is when it's just routine & you're not forcing yourself to go, that is a joy!