CHICKEN.
I literally just have 10-12 prep bowls in the fridge and freezer at any time. Hungry? Eat chicken.
Hard to build and maintain muscle mass when you're older. Gotta focus on not losing what you have. And not losing what you have requires a shitload of protein. Activity level drops when you get older, so not getting fat requires less calories and more nutrient dense food. Grilled chicken is top of the list for both of those goals. Find a marinade or spice combo you like, taste is subjective.
So, yes, literally, my lunch 5-6 days a week is 6oz of grilled chicken and 2.5oz of blueberries to keep the sweet cravings at bay. Ends up being just under 300 calories for 50g of protein.
It's also is pretty fucking cheap when you think about it. Chicken breast was on sale for $1.99lb last week so we bought 10lbs.
Edit : forgot the most important part. I just feel better eating 200g of protein every day. I'm not saying mentally, im saying literally I'm in less join pain (probably as a result of working out more, but whatever), and the biggest one for me is I struggled with stomach and small intestine ulcers for over a decade with repeated 2-3x a year flare ups for months at a time and those have completely gone away.