What's the fastest way to burn fat and build muscle?

2 weeks is super fast. You should consider talking to a personal trainer who may be able to hook you up with something-- I would be concerned that you could end up injuring yourself if you just try some crash diet.

You can certainly build up muscle in 2 weeks, it's hard to burn more than a couple of pounds of fat a week.

Hit the gym 5 days a week. Don't skimp on your leg workout because your biggest muscles are in your legs and thus burn the most calories when worked out. Also, don't substitute the gym with a run. Running is good, but going to the gym will burn more calories and slim you down faster. Working out this much will make you hungry, but try to not eat more than you do already. If you have the willpower then try and eat a little less than you already do.

Just make sure you cycle your muscle groups -- especially if you work out a bunch.

But you've been "asked to change your appearance" for a play opening in 2 weeks? Are you going to rehearse in that time? If you're hitting the gym 5 times a week you're going to have a hard time walking, let alone trying to do any meaningful work rehearsing -- especially if you're "not very fit" and haven't been lifting regularly..

It sounds like they have totally unrealistic expectations -- watch what you eat, lift moderately, drop a pound or so, but don't kill yourself. Trust me, it's a lot harder to act with a pulled hamstring.

Weights temporary elimination of simple carbs - breads, sugars, starches etc.

If you're trying to do something drastic in two weeks, know that it's going to do harm to your body. Rapid changes are always harmful (and it won't last, either).

Drink water by the gallons. Continue to drink it until you feel full. Eat nothing. I really mean nothing. Go on a fast. Essentially, the only input into your system should be water. What happens is that after two and a half to three days, your body goes into a state where it will draw all its energy from your fat reserves and burn fat like crazy. Hit the gym for no more than 1 to 1.5 hours a day. You won't have the nutrition to be there any longer without passing out.

I've done this twice before and it's a bit painful but it gets you the results you're looking for.

You won't tone up in a way that you'll be building muscle much. You'll be toning up in that your current muscles will be tight and responsive (from working out) and all the fat that hides the muscles will be gone.

Again, I remind you that it's not good for your body and that it's painful. But, I've done it twice and would do it again: for drastic results, like the ones you need, it works.

I agree with the person who advised you to consult a professional trainer, and would further add that you also consult a physician if you're looking to make drastic changes in such a short time.

There are so many other factors that may make certain activities dangerous for you, depending on your age, gender, prior health conditions, etc.

Having said all that, you might want to check out this short YouTube video, which provides a glimpse into the workouts that the actors in Frank Miller's 300 had to go through to get the physiques they needed for the roles: http://www.youtube.com/watch?v=w6Eyg32W4aE

Oh! And something to watch out for-- certain industrial pollutants the body deals with by storing in fat-- if you burn fat too quickly they can enter your bloodstream too fast and make you sick (or worse). (You likely won't have that problem, but another good reason to talk to a physician)

I know this is much too late of answer, but for all those future weight loss folks. It is very important to have and maintain a low glycemic diet and drink at least 64oz of water. Water intake is so key in weight loss