Ok, I've heard that muscle weighs more than fat and that weight training also builds muscle density. I've lost 47 pounds in 5 months. In the last month I've only lost 1 pound. This just so happens to be about when I added hills to my walk and weights. However, my clothes are looser, and every person I see comments on my continued weight loss. I didn't take measurements before, and I wish I had so i could have more objective ways of measuring my results....BUT...is it possible that the slowed weight loss is due to muscle gain?

It might be part of the reason. The average woman can gain about 0.25 lb of muscle per week, or slightly faster if you're new to weightlifting.

The scale is useless if you're predominantly going to lift. Muscle will not provide a good scale result. The tape measure will be best if you're going to be a serious iron pumper. I use both since I'm lifting 3x per wk.

Tbh the measurement of the physique is more the standard for this era. To avoid frustration maybe experiment for which is best for you!

I diverge in opinion from the others here. From what I've read, the MAX muscle a normal woman can gain in a month is 2lbs (assuming normal hormones and she's not using steroids or something along those lines). At the same time, you can safely lose 8-12 lbs of fat in a month (more if you're really overweight, less if you're closer to goal, of course). So unless you're really close to goal, the stall in weight loss is probably due to your diet. In the first week, when you're really sore, it's probably water weight because DOMS pulls in water to the muscle to aid the healing process. And that can be around 5 lbs of water. But once you've adapted...and after a month, you should have adapted...if you're not seeing fat loss then I'd wonder if you're not either rewarding yourself with food or experiencing higher levels of hunger due to the weight training and thus eating more. I'd take a super close look at your diet. Again, this assumes you have weight to lose. If you're really close to ideal weight, you're not going to lose much regardless of what you're doing.

Yes, it can be a reason why you did not loose so much weight this week.

I felt the same thing happened to me

Very possible

Muscle doesn't weigh more than fat, it is however more dense than fat meaning muscle takes up less space than fat at the same amount of weight. when working out its important that you track inches lost in addition to the scale.

The problem I run into when I workout without watching what I eat very carefully is that excercise, especially HIIT cardio makes me hungry. Weights make me crave more protein, and as long as I adjust my Macros for training (eat more protein when training, especially on weight days but) I don't really over eat, but if I don't make that adjustment I end up eating more calories than I should because I feel hungry. Either way I have to make a conscious effort to eat less because being active really drives up my hunger. So i have to be careful not to eat more and over-consume calories when training.

That said I haven't lost weight in months but I have lost inches, so I'm losing fat but VERY slowly because i keep falling off my eating plan (stress/holidays/illness...) .