I always say - get as far with your body as you can with good nutrition and exercise - when you hit a plateau or feel like you are not progressing any further - then you can throw in the fasting tool. You want to keep these things up your sleeve so when you are struggling with the last 5 - 10kg you have another tool to throw in and shock your body with (body gets used to regime quite quickly and responds very well to new stimulus). You dont want to be using all of your tools and plateau before your goal weight - with nothing else to throw at your body. Fasting is a good tool for this!
When you are at your goal weight you might then want to reduce the fasting to maybe once a week for instance just to maintain - or even see if you can get away with none at all (see what your body does). Like I say, you dont want your body getting too used to any set regime like fasting tuesday and friday - change it up - stop it for awhile, see what happens etc - test how your body reacts.