Not 60000 but 6-7k.
It really really really will come down to food and style of training. It depends on your goals and your training logic. By training logic you need to be able to accept and rationally understand how things work with regards to training.
IF you want to finish a half marathon thats easy, with little to no muscle loss. But thats just FINISHING.
If you want to be competitive, get down around 1.5 hours. You're going to "lose muscle". Technically you aren't ever "losing" muscle, unless you went in and surgically removed it. You're just removing a lot of the hypertrophy (fluid storage) in your Type IIa-x fibers. Really what you'd be doing is pulling your IIas into a more oxidative adaptation vs glycolytic adaptation. So, you're losing that hypertrophy potential. Again this all depends on the extent and style of your training.
The other buch is eating. Yes, it is true I eat about 6-7k a day, and wake up in the middle of the night to eat as well. I am a semi-anomaly, but not totally out of the ordinary. I am smart about my nutrition and have always kept my intakes high. Even at that type of intake the heaviest I'll hit is off season and thats about 178 lbs at about 9-10% body fat. That is eating everything in sight. 4k of it is very very clean 2-3k of it is all just whatever I can get my hands on, down the gullet. When I get to race weight, it gets to be all clean and thats how I'll lean out to about 165-167 @ 4-6%.
I'm not one to shoot down goals, but if you want to be really jacked and still hit competitive half marathon times, you've got another thing coming. You would've been running halfs already, if you were capable of doing that.
So you've got to decide, do you want to to just finish or do you want to be competitve. If you want to really go out and smoke the course, you've got to check your body image at the door.
I'm a long course triathlete, and yes, I'd love to be huge, but I love my sport and part of that is just understanding, being good is being built for the sport. You've got to optimize yourself for what you do. I'm one skinny bastard, but I'll tear up a course.
REALLY figure out your goals and then shoot me a PM or post on here.
Also, talk to Eric Cressey about this in his locker. He's my coach, he'll definitely be able to give you SOME insight into it. The rest of it is proprietary info .