I'm an 18 year old male, who, although not unhealthy weight (originally 182 lbs) saw that too much of was in fat. Also for the past two years or so I have been doing crunches fairly regularly, and thought that reducing my overall fat might result in a nice six pack or something like it.
So now, jump to about a week ago, I got serious about this and started to increase my running (from a few miles a couple days a week to daily at 4 miles) and increase my ab workout slightly. Most radically though, I restructured my diet a lot. Before I would eats lots of relatively healthy food (pasta, yogurt, salmon, whole grain bread), and eat it till I was stuffed. Now I just eat a sorta predetermined small increment of food (usually based around salmon, yogurt, or eggs with some carbs/veggies) at each meal time, and outside of that I snack on vegetables and some fruits.
So with this strategy for about a week, it seems I have lost 7 pounds, with a fairly constant rate of about one pound each day (weighing myself each morning). I don't have a particular weight goal, just an overall reduction in body fat (which I don't have a direct way of measuring except looking down at my stomach :P) I don't think much of it is water weight (I always pee clear!)
So I suppose my primary question is how unhealthy is that sort of weight loss? It seems looking around most sources quote around 5 pounds a month as healthy... My primary worry is that loosing too much means that more of the loss is coming from muscle mass. I don't want to sacrifice all the work I've put in on my abs! Or will the fact that much of my diet is protein (~50%) protect my muscles somewhat? Other than that, so far, I feel great and have more energy than I have had in a while!