Is 2 hrs of walking daily too much? i've heard it could cause muscle loss

Possibly ok: Walking 2 hours a day might be ok if the following are true: you have built up to this distance/duration gradually and don't feel during or afterward; nothing hurts when/after you have walked this much; you are not obese such that this much weight bearing could be a strain on your joints. Consider how our ancestors were likely walking around all day! Go at it slowly, listen to your body. Stay well

Not likely: Unless your caloric intake is so low that your are burning more calories then your are taking in. That's a great habit for keeping G you active. I congratulate you on your efforts.