Apologies for the newbie question about muscles, but...

From that little of exercise you wouldn't see any muscle being generated that would cause weight gain (NOT trying to put down your exercise at all, please don't read it that way)

To me it sounds like you are still taking in far too many calories. I would wager to bet that you should probably be in a 1500-1600 calorie range to loose 1-1.5lbs per week with the little exercise you are doing.

It's also going to be about what types of food you are eating and when, calories are important, but what type of calories is wayyyyy more important.

Take a good look at the exercise you are doing. If it's significantly more movement than before MFP, yes you can increase muscle mass (even slightly). Also things that can "plateau" your progress: water shift (you may be sodium sensitive), underestimating your intake, your TEE calculation is not true to your real TEE (calculation are just estimates), overestimating your exercise, decreased lifestyle activity (i.e. increased sedentary time).

Want to shock your system? Try some interval training (i.e. alternate jog with your walk, or stairs with flat). Try 20 sec as fast as you can, 10 sec slow (called "Tabata").

Want to increase your lifestyle expenditure of energy? Walk instead of drive, stand instead of sit, take the stairs instead of the elevator, during TV commercials do air squats, FIDGIT when you are sitting (don't sit still).

kona
Registered Dietitian, Crossfit Masters

Take a good look at the exercise you are doing. If it's significantly more movement than before MFP, yes you can increase muscle mass (even slightly). Also things that can "plateau" your progress: water shift (you may be sodium sensitive), underestimating your intake, your TEE calculation is not true to your real TEE (calculation are just estimates), overestimating your exercise, decreased lifestyle activity (i.e. increased sedentary time).

Want to shock your system? Try some interval training (i.e. alternate jog with your walk, or stairs with flat). Try 20 sec as fast as you can, 10 sec slow (called "Tabata").

Want to increase your lifestyle expenditure of energy? Walk instead of drive, stand instead of sit, take the stairs instead of the elevator, during TV commercials do air squats, FIDGIT when you are sitting (don't sit still).

kona
Registered Dietitian, Crossfit Masters

If you are at a deficit, it is unlikely you gained much, if any muscle. If you just started weight lifting, you may see a small amount of newbie gains, but it will definetely not be 3 lbs of muscle gain. My guess is that it's mostly water weight that you're seeing. Try weighing yourself after a rest day (and don't eat too much sodium or go carb-crazy on the rest day), first thing in the morning, and comparing that to your previous weights. And avoid the scale during your TOM.

My other thought is that you should try to minimize the effect of some estimation errors. For one, use a food scale. Being off in portions can really make a difference in calories. Two, if you "eat back" exercise calories, try to eat back no more than 3/4 of them. MFP tends to overestimate those (and even some HRM can be off). If your TDEE is, say 1800, and you are trying to NET 1500, these two mistakes alone can cause you to be really eating at your TDEE instead of a deficit.

If you are not used to exercising, I would not recommend you jump into Tabata or HIIT intervals. You will see enough of an improvement by simply building up your health base-- i.e. just getting some regular exercise. If you started off walking for 15 mins, try building up to walking for half hour. If you can walk for half hour, try doing running/walking intervals for 20 minutes. Work up to running for half hour. And so on (you get the idea). There's no need to jump into intense workouts when you're not relatively fit.

http://www.bodyrecomposition.com/fat-loss/of-whooshes-and-squishy-fat.html

Yes, it is doing something to your muscle.s
Filling them with water.

check out the book New rules of lifting for women.