How much weight can be lost by not eating?

The simple answer is 3.77 lbs. But life is rarely that simple. It takes a negative difference of 3500 calories to lose a pound of fat. If you ingest no food for six days you could potentially lose 3.77 lbs. However, if you fast for an extended period your metabolism will drastically slow down preserving your fat. You will also begin catabolizing muscle, not a good thing. You would actually end up fatter than when you started at least in terms of body fat percentages. 135 lbs for a 5'6" person is a normal weight. Your time is better spent learning to accept yourself and maintaining a positive body image. If you still desire losing weight, join Weight Watchers or speak to your doctor. It isn't uncommon to eat sensibly on Weight Watchers and lose 4 lbs in your first week anyway. Increasing your exercise will also enable you to lose significant amounts of fat while still eating. Fasting for six days is just plain dangerous.