Firstly, a massive well done on your weight loss, OP; fantastic achievement 
I'm 51 years of age, my BMI is around 20 and body fat 11.5%. I lift weights three or four times a week (aiming for five times) and walk a round trip of four miles to work Monday to Friday.
Foodwise:
BREAKFAST
fish or eggs with salad/vegetables' OR fresh fruit
LUNCH
homemade protein based lunch with salad/vegetables, eg Thai quorn curry, three bean stew, lentil dhal — that sort of thing
DINNER
steak/chicken/fish with a small portion of brown rice/pasta (on training days) and vegetables/salad
SNACKS
a couple of pieces of fresh fruit
DRINKS
tea/coffee on tap all day: it's a vice
water x two litres (minimum)
EATING OUT
I love eating out. I relax the rules when I'm out but I don't go mad. My digestive system is not what is was when I was younger
I'm likely to go for red meat (treat)/fish (I love fish) and vegetables, rather than burgers, pizzas and the like. If I'm dining out properly (a date sort of thing), rather than a bite out with friends, then I like to finish with the cheeseboard 
I very rarely eat junk food, don't eat sweet things and don't drink alcohol.
Reading back, it does sound rather grim but actually it's way easier and more pleasant than it sounds. If I deviate for any length of time, I (a) put weight on and (b) feel shit (physically). Sad. But true. I was asked previously whether, seeing as I'm 50+, I couldn't just be happy putting on a few pounds and being a size 12
. My answer back then was: 'No. I like me just the way I am at size 8'. I haven't changed my view since.
What I have noticed on this thread is the wide variation in what people can eat to maintain their healthy weight. We're all different and just need to find an individual strategy that suits. There's no one approach that will suit everyone.
Incidentally, I too have been much heavier in the past, having lost over six stones during my late 40s. Maybe that's why I'm so keen to stay healthy now.