Haha, from October 22nd to the November 2nd (that glorious day on which I finished my HSC!!) I lost 4 kgs.
That was COMPLETELY anxiety related, lol.
I didn't sleep properly, and really didn't feel like eating much for 2 weeks.
But all up over my HSC year I ended up loosing 12kgs. Surprisingly all of it was blubber lost (yay!), and I gained some muscle, (but not much - around one kilo?). But that was just because of lifestyle changes, and looking after myself through the year.
So yeah, don't let HSC be an excuse to pork up!!
Take this as an opportunity to learn some great time management. If you can stay healthy this year it's a great practise for balancing work and socialising and uni later on =]
And you've only just started your HSC? There's a lot more to come, so why not use these hols to get into a health and fitness regime?!
Best of luck =D