Since when did you have to weigh 150 or less to be allowed into the program?
I've seen navy seal training camps on discovery or whatever channel, and I'm pretty sure every guy I saw on there was way over 150.
I'm 5'8 175, and I couldnt even think of wanting to weigh 25 lbs less heading into boot camp, not to mention 65 lbs less.
What the hell.
Anyway, to answer your question: No, fasting is the most horrible thing you can ever do. EVER. What you should do is definitly get rid of all your sugary crap foods, get your diet in order, and you will see much better results from that.