After about a year of bad nutritian and virtually no conscious exercise I have been eating better and working out for about 4 weeks (cycling, a walk/jog program and a group fitness class that has very high reps of light weights - bodypump for those familiar with Les Mills program.)

The scales have not budged at all.

I am feeling heaps better, I think my clothes are a bit loser and I am feeling better about how I look so at this stage I'm not complaining (although I do need to drop a bit to get into the healthy bmi range) ...but my question is - how much muscle can/would a woman realistically gain though a moderate exercise program (ie not one that includes heavy weights with a specific aim of bulidng muscle size).

I don't have a car so walk and cycle everywhere - so I wasn't completely sedentary even when I wasn't working out as such.