Why am I losing weight since I quit smoking marijuana?

Hi - I have been smoking marijuana for 5 years almost everyday all day. I just quit and I am now on day 7. The first couple days I suffered from an extreme loss of appetite and nauseas stomach, so I forced myself to eat. I fell I am able to eat normally now, however, I keep losing weight. My diet has always been the same, I would eat the same amount of food on marijuana as i do now since i quit. I eat very healthy and I always have since I was on marijuana. However, for the past 4 years I have been going to the gym and lifting weights and i would always smoke marijuana a couple hours before i would go, i was never high when i would go to the gym though. Over the 4 years i have been lifting weights i have put on about 30 lbs of muscle and mass. Now i find myslef since i quit to be losing weight however my diet has not changed, i still eat very healthy and consume jus as much food as i did while i was on marijuana. I have not been to the gym since i quit though. I don't like that i am losing weight. Is there anyone that can provide some insight on this, I would like to start gaining weight again i am down like 7 lbs and want to get it back. I hope someone can provide some feedback. Thanks.