I've been like that for much of the past 18 months. Haven't been to a gym. Exercise consists of walking and hiking. Have had sex like twice in the past year. Only talk to friends on the phone. I work at about 25% of the capacity I was doing three years ago.
Honestly, it's lonely. Very lonely. My dog is my sole companion. I am reinventing my life shortly, up to and including buying a professional services business. I almost fear I won't be able to function in any of the categories you mentioned. I've been clean of illegal drugs for 18 months and benzos for 14 months. I drink occasionally, and usually regret it. Had 4 drinks last weekend - first in some months - and all I could think about was ordering cocaine. Still smoking cigs.
I am seriously considering joining AA or NA just to learn how to socialize again. I'm not sure my mind is capable of increasing my work load. Eventually, I will have to hire and manage people. Not sure if I can do that again.
So in short, dropping out of life is easy if you can afford it. Climbing out if you want to seems to me to be a challenge.