I’ll be 40 at the end of the year. I have been eating lower carb for a couple years now, but I’ve never done any sort of calorie restriction diet in my life for more than a couple days. I’m pretty good at listening to my body - the trick is to give my body the right inputs so that it asks for the right things! Forcing myself to eat lower glycemic index carbs to reach 25% of calories kept messing with me seriously, and I would rebel by either skipping the carbs or going too far the other way. I think I’ve been accidentally fat adapted in the past when I rebelled against the carbs in my prior WOE, so for me the big hurdle was knowing how to get back and stay there.
Keto is my happy place, food wise. It is how I want to eat when I’m not bombarded by sugar-driven cravings.
I’m looking for a 50-55 pound loss from my 5’7" frame, but if I hit the point where I think I’ve lost enough I will happily stay there. I have a dozen or more people on official skeletor watch to tell me if I take things too far. 
Things are going well so far. Very well. Yes, I’m a unicorn. But keep in mind that I have never calorie restricted and I’ve been healing my body from serious digestive issues over the years. Keto seems to have healed me of IBS-D as well as increasing my energy levels.
Great to see there are so many of us on either side of 40 here! I do think it is nice to get us together, as some of us may still have more children in the future while others are definitely physiologically done with that stage. We probably all still have a bit more metabolic resiliency than those women a decade older than us are facing.