This morning I did get out of breath a few times, but if I felt overwhelmed I just went down into child's pose to rest for a few moments to rest.
The classes are anywhere from 75 minutes to 90 minutes - I'm going tomorrow morning for the 75 minute class.
It may not be feasible everyday; I'll have to listen to my body. But I always feel so good after yoga, it's like "spiritual food" for me. I did read at one point that hot temps while fasting aren't advisable, but I enjoy the heat...makes me feel very nourished.
Aside from my white and funky-tasting tongue, I don't even feel like I'm fasting right now, so I was thinking I'll just do what I usually do everyday - except much more sleeping and rest since I don't have to work right now.
I'll see how it goes tomorrow and report back. :-)