The last I remember when working out was - PROTEIN, FATS, and some low index CARBS. I got fairly big for my small frame. Normal weight was 165lbs at 5'10". I got up to 190 with definition. My wife lost her most weight on the above which everyone knows as Atkins. Keto allows for a little more carbs. Could be wrong.
Nutri-System can also work if you stick to their plan of eating all the day. It works by increasing your metabolism, but is a pain to stick to and expensive.
Bottom line for me: Chicken salad&cheese with Triscuits (fiber), pro-biotic yogurt, and walking the treadmill 2-3 times a week. I'm 71 and feel I could take on a 40 year old. Although, probably get my ass kicked.
Forgot to mention a nasty burger every other week. And then there WERE the times out at a restaurant for a Steak! Looks like that will be possible in the near future! Yeah.