Muscle & weight loss?

I'd suggest adding in some strength exercise now.

Particularly for us as women, muscle loss increases future risk of bone loss, which is a major health/mortality risk as we age. Simply being overweight seems to decrease osteoporosis risk (but is overall not health-beneficial, of course). A way to counter that risk to bones, from being lighter bodyweight, is to stay strong, in addition to getting some impact exercise if the body allows, and appropriate nutrition.

Further, when we're overweight/obese, we tend to have more muscle mass than a similar-frame person of similar activity level who has never been overweight. By doing strength exercise during weight loss, pretty much the worst that could happen is that we keep more of that muscle (that our body will de-prioritize and be more likely to lose as we get lighter, if we don't keep challenging the muscle). Because muscle is relatively slow and effortful to build under the best of circumstances - perhaps especially so for women and those of us with some age on the odometer - keeping what we have is an efficient strategy, IMO.

Besides, as sijomial wisely says, beginners are more likely to be able to gain a little mass, even in a calorie deficit, especially if that deficit is sensibly moderate.

Another fact: Strength gain precedes and is faster than muscle-mass gain, via neuromuscular adaptation (basically, better recruiting and using the muscle fibers we already have). Strength is useful in itself, both in daily life chores, and potentially in being able to advance our cardiovascular exercise intensity. If you haven't strength trained before, or not in a long time, you'll get strength benefits quite rapidly.

Starting strength exercise, especially as a beginner, doesn't need to be some hugely time-consuming thing. Even half an hour 2-3 times a week can have material benefits. Yes, it burns fewer calories per minute than most cardiovascular exercise, but it has other benefits as mentioned above.

With respect to the comment above about some people not enjoying strength exercise: I'd raise my hand in that roll call. In my regular life, I'm lackadaisical about strength training, to my detriment (don't take me as a role model - eek!). I usually strength train (lift weights) a bit in my rowing off season, but usually not much beyond that. However, during weight loss, I did make it a point to put strength training at a higher priority, do it more often and more consistently, for the reasons mentioned above.

Please don't let my bad attitude infect you: Many people enjoy strength exercise. Even I enjoy the effect of feeling stronger, when I have the patience to reach that point. Over and over, people here report finding the actual training activity to be fun. While that's not universal, please do keep your mind open to the possibility that you'll be one of them.

I'm sure you know that there's a thread here about picking a strength training approach:

http://community.myfitnesspal.com/en/discussion/10332083/which-lifting-program-is-the-best-for-you/p1

In case you haven't had an opportunity to read it, I'll point out that the title is a little misleading: It's not just lifting programs. There are also bodyweight programs discussed that can be done at home, with minimal or no equipment, if that approach is more appealing.

I don't think I've ever seen a post here from someone who said "I'm sorry I started strength training during weight loss", but I've seen a bunch that said "now that I'm strength training in/near maintenance, I wish I'd started doing it from day 1". Food for thought?