i lost 13.2 pounds (of fat i am very certain of this) in a month for doing HIIT (the intermmediate 1 minute rest and 20 second 90% HR for 25 minutes <5 minutes warm up>), weight training, and "slow cardio" 4 times a week (and burned myself out for around 4 days before getting back) and when I asked the doctor he says that there is a maximum amount of pounds of fat we could lose and on my weight class it's a maximum of 3.5 to 4 pounds a week and I still didn't meet the maximum amount of fat I should lose. This is in a roughly 1000-1200 calorie a day alotment with no sugar (the refined one, apples or some sweet fruits are ok) no salt, and no simple carbohydrates. I guess what I'm trying to say is (aside from I killed myself yet only lost 6 kilos) our metabolism isn't really universal. Some are fast and some are slow. There are alot of nice people here who could lose more than I could when given the same time frame but I know we are all in the same track of losing weight and being healthy.
Muscles... now that's a different story. Muscles are good because they need energy to function and the more you have of it the more it is likely that your metabolism would be higher! That's why cardio training and weight training are considered very effective when done together. If I were you, I'd be happy to have more muscles! I guess when you are done with losing weight, then you can start thinking about those muscles. Muscles are far very easier to lose than fat. Just being inactive for a given time, your body would realize that it won't need the muscles anymore then it would start to catabolize itself. Wow that was long. ^_^