Danged whippersnappers! GET OFFA MY LAWN!!!
I think I hit sort of a trifecta when I was 35.
Me and the Mrs. enjoyed many a sumptuous meal and didn’t do a hell of a lot to burn it off.
I started working in NJ, which necessitated a switch from a pedestrian to car lifestyle and didn’t leave a whole lot of time for exercise.
The usual slowing down of metabolism in one’s 30’s.
As a result I really packed on the pounds and while my health currently is good, it’s extremely hard to lose that gut. I’ve been able to hold steady on my pants size, so that’s some consolation.
Um…yeah. 
I turned 40 in June. In September I got bifocals. In August, I started going to the gym to try to rectify a 40 year sedentary lifestyle (though I’m not more than about 15 lbs. over the weight I’d like to be, which I think is pretty good for a bookworm). My knees are shot all to hell (which they have been for years, but they’re hurting a lot more nowadays) and my wrists, shoulders and back hurt a lot more now. Oh, and the arthritis in my fingers that’s been there since my 20’s is giving me hell as well, much worse than ever before.
However, I’m watching my diet, firming up, losing weight (slowly), feeling more energetic, and popping ibuprofen like a mad thing. 