Very good post on L-glutamine.Also worth looking at supplementing with:

1) Branched chain amino acids (BCAA's). The release of these by the muscle gives the body the general signal to stop the conversion of alanine into glucose (gluconeogenesis) . Ideally you would not want gluconeogenesis to occur for an extended period of time because this is the process of breaking down muscle tissue and unless you immediately supplement with a high bioavailable protein and carbs post workout you lose muscle. Lost muscle slows your metabolism. Of course supplementing with l-glutamine will aid against this. Back to BCAA's there are three: l-leucine, l-isoleucine and l-valine. When working out intensely BCAA's work to spare muscle tissue by becoming a fuel source. So with L-glutamine and BCAA's, having a high quality protein diet that supply both can help with supplying fuel to working muscles.

2) Beta Alanine. When you exercise at high intensity levels, your blood pH levels fall (your blood becomes more acidic). When this happens you feel fatigued, get that burning sensation and begin to feel like quitting. Beta alanine is another amino acid that helps to increase your blood's pH making it less acidic and thereby allowing you to workout a little longer and make things a little easier.

3) Glycogen (carb) loading. Good if your an athlete or workout in high intensity zones (like doing intervals, high set and high repetition weight training etc.). Would probably want to skip though if you're seeking to lose bodyfat.