I have been doing keto for a little over two months and I love it. It is a better way to eat I think and a great way to loose weight. I love dark chocolate and yes it is great for many health reasons as well as the reason you mentioned. I can eat dark chocolate so I am fortunate, the bitter the better I say.
I have the opposite problem; trying to gain weight. But they're not that far apart so I feel I can relate. My metabolism will probably just dial down in my late 40s like my parents :)