Losing fat vs. muscle?

You're losing both.

If you eat an appropriate amount of protein and do resistance training, you can minimize the loss of muscle.

Well about that, exercise regularly, measure each loss, observe needs.

Good question.

According to http://www.bodyrecomposition.com/announcements/women-training-and-fat-loss.html/

Women lose less lean body mass than men. In addition, the higher your body fat, the less lean mass you'll lose.

Take your measurements. If your belly fat and waist are shrinking, you're losing fat. If your arms and thighs are shrinking you could be losing both, how do you know? If you're like me and prefer to see some numbers, then check your body fat at the beginning, determine your lean mass and fat mass. And after losing every say 5 or 10 lbs, measure again and recalculate and you'll know if you're losing lean mass. Your muscle is a fraction of your lean mass so you can't really know exactly how much muscle you have. Your goal is to keep the total lean mass number as constant as possible as you lose weight.

My example:
I use the Navy method calculation where you just need height, neck, waist and hips. It's what I've been using because it's consistent. http://www.calculator.net/body-fat-calculator.html

Started at 152 and 31.7% body fat in January.
Fat Mass=48.2 lbs (actual fat)
Lean Mass=103.8 lbs (bones, organs, muscle, fluid etc)

Current - 128 and 20% body fat.
Fat Mass=25.6 lbs (down 22.6)
Lean Mass=102.4 lbs (down 1.4)
Total weight loss = 24 lbs of which 5.8% was lean mass and 94.2% was fat mass.

It's considered normal for 20% of weight lost to be lean mass lost. Mine is 1.4/24 = 5.8% which is way below the normal expected. Why is this? Because I had a high body fat to start with. And, I didn't even do weight training. I just did cardio 95% of the time simply because that's all I felt like doing. It was either that or the couch. Also, my protein is roughly 70-90g/day or 15% of my diet. Carbs are 70-80% of diet and currently whole foods, plant-based.

Short story - don't worry about it (unless you're at extra low body fat and really ripped right now). Just eat a reasonable amount of healthy whole foods and exercise and if you're at a deficit, your body is smart enough to chomp on your body fat before your precious muscle.

http://community.myfitnesspal.com/en/discussion/10348858/losing-fat-maintaining-muscle-tips

makes it simple to calculate just found it now and was really helpful