Many exercise physiologists and nutritionists believe that a loss rate in excess of 1% of bodyweight invariably results on muscle loss.
You might check out the weight loss calculator here:http://www.prime-fit.com/calc-timetolose.htm
It suggests that an aggressive weight loss program would get you there in 27 weeks (6 months and 1 week), a far more sustainable approach would take 54 weeks, or just over a year.
You have 7 months and 3 weeks - so theoretically it is possible for you to lose the excess body fat and sustain your lean mass. But you'll have to be very cagey to do it.