Don't starve yourself, that's the best way to burn muscle, not fat.
And the trash bag thing just makes you lose waterweight, not actual weight. It's something wrestlers and boxers do in order to lose weight fast before weigh-ins. The weight doesn't stay off, you gain it all back the next time you have something to drink. You'll have to change your habits in order to get what you consider "fit."
But it bears repeating, 5' 10'' and 150 is not fat. If you think it is then you may have some serious self image problems.