Is it possible to lose only fat and not muscle?

I am female, 21, 5'3" and according the Weight Watchers scale I use, I'm about 137.2 lbs. and have 29% body fat. That was in the "healthy" range as defined by the manual that came with the scale (21-32% for someone my age), but I would like to get in better shape, or at least lose enough fat that my thighs stop jiggling so much. I did some calculations, and figured out that if I lost only fat, I'd be in a good body fat range between 123 and 130 lbs. (21-25% body fat). I was wondering though, is it possible to lose only fat when you are losing weight, or does some muscle always leave with it? And would that require dieting at a slower pace or losing weight more slowly? What kind of diet/exercise plan is good for losing fat and maintaining muscle?

I have been eating lots of protein and doing weight lifting and resistance training in addition to my usual cardio in the hopes that I would not lose any muscle, and I can definitely tell I'm in much better shape than I was 20 or 30 lbs. ago (don't know what my bf% was then), but I would like to get in better shape and lose fat as efficiently as possible. Preferably in the hips, butt, thighs etc. rather than the chest, because I'm starting to get flat-chested and bony on top, but my whole lower body is still rather pudgy. I'd like to keep up with losing a pound or more a week, if that is possible.

Do genetics make it difficult for some people to maintain a lower body fat percentage without working out three hours a day? Because I'm worried I might be one of those people.

your body type and family will dictate how easy it is for you to lose body fat. it sounds like you have everything right with your diet and exercise. so keep it up, and you will be fine.

I think as long as you are eating the right amount of calories, and a healthy, balanced diet, then you do not have to worry about losing muscle mass. Be sure to keep weight lifting and incorportating plenty of protein in your diet.

Working out 3 hours a day is a bit excessive, IMO. Be sure to give your body rest days so your muscles can rest and build themselves. Rest days are just as important as workout days. Your muscles need time to rebuild.

Here's the rule of thumb I've found to be closest to the truth:  if you're doing everything right (and it sounds like you're not missing any vital piece of the puzzle), you can lose around 1% of your body weight in fat per week with minimal (even no) lean mass loss.  The less fat you have, the more that breaks down, but you're not there yet ;-)

Of course the milder the calorie deficit (= the slower the fat loss), the easier it is to preserve lean mass.  If you're close to calorie balance, it's even possible to lose some fat and gain some muscle at the same time.

While it's obnoxiously marketed, Tom Venuto's "Burn the Fat, Feed the Muscle" is the single best guide I know of covering all essential aspects of a fat-loss, muscle-preserving program (diet, nutrition, weights, cardio, measurement, and motivational techniques).  I don't know whether the review linked to there is truly independent, but I have no connection with the book or its author, and I largely agree with all that review says.  The book simply is that good.

Electronic fat-measuring scales aren't particularly accurate, but they can be quite useful anyway if you can get consistent readings from yours.  Here's an article with tips for increasing consistency.  If at all possible, ask a trainer to measure your percentage with skinfold calipers at least once, so you get a feel for how far or close your scale gets to a more accurate (for most people) method.

Something to watch out for:  percentage alone can be misleading -- it's quite possible for body fat percentage to fall even if you are losing significant muscle mass.  What you need to do instead is use the fat percentage to compute your total pounds of fat weight and total pounds of non-fat weght.  For example, if your percentage is 29% and you weigh 100 pounds, you carry 100x29% = 29 pounds of fat.  Then 100-29 = 71 pounds of your total 100 pounds is non-fat ("lean") weight.

Now carry that example a step further:  suppose you actually lose 2 pounds of fat and 2 pounds of muscle.  Then you're down to 100-2-2 = 96 pounds total, with 29-2 = 27 pounds of fat, and the fat percentage is 27/96 = 28.125%.  So body fat percentage dropped nearly a full point despite that you've also lost a significant amount of muscle.  Body fat percentage alone can be very misleading for this reason.

I plot both weights (fat and lean weights) in a spreadsheet, and ask the program to compute trendlines ("least-squares linear regression") for both.  That's an effective way to filter out measurement noise, and electronic scales in particular can give disconcertingly inconsistent readings across very short strectches of time due to all manner of random variables you can't always control (mostly body hydration level and water distribution within the body, but also subtler things like room and skin temperatures).

Unfortunately, while you have a great deal of control over which muscles grow and how much, where your body prefers to store fat is determined by genetics.  The only ways to lose fat in a particular area are to keep losing fat period, or to get it sucked out by a plastic surgeon (liposuction).  Women often have the problem you're having (well, men do too, but they don't see losing their own chest fat as being "a problem" ;-)).  It's discussed frequently here.  For example, the "losing weight and shrinking boobs?" thread in this forum is still going strong after 75 messages.

Thanks for all the helpful advice!

I don't work out 3 hours a day, and I don't really want to. Right now I'm going for about an hour five times a week. I wanted to figure out how good of shape I could stay in working out three times a week and walking every day, since I'm a student and most of my work is sedentary. I wasn't sure if it was realistic to stay very lean, given my schedule and my body type.

I didn't think I could spot reduce fat, but thought I would ask anyways. My concern is more practical than aesthetic, actually. I have a hard time finding dresses that fit me because my lower half wears a bigger size than my upper half.

Clarence Bass is still in phenomenal shape at about 70 years of age, and maintains it working out only twice a week (one weight day and one cardio day).  His approach is unusual, relying on short but very intense workouts.  If you'd like to know more about his approach, visit his website.  In fairness, I've read most of the articles on his site, and he certainly appears to do a whole lot of other exercise that isn't counted in his "official" two workouts per week.  OTOH, he isn't content to maintain -- he's still setting personal records despite his age.

You certainly don't need to work out 3 hours a day to maintain -- or even to improve dramatically.  Mainstream minimum current recommendations for maintaining cardiovascular health appear to be 20 minutes of moderate-intensity aerobics 3x a week (different sources disagree on how much is "desirable", but nobody recommends less than that).  In addition, 2 45-minute whole-body resistance workouts per week should be more than enough to maintain muscle.

Add that all up and it amounts to 2 1/2 hours per week.  Note that nutrition is a key part of the equation too -- not even philosophers can talk their way out of the old "you are what you eat" truism ;-)

I gotta say tgpish... you sure do have useful replies. I really admire your ability to keep giving thoughtful, clear, and super-detailed answers to what amounts to the same question over and over again (which I asked a few weeks ago too!!).

And congrats on your weight loss so far, geistjagerin! I'm trying to do the same thing you are but it sounds like you're a little farther along, I just started lifting weights 1 month ago. I'm 22, 5'6", 152lbs. 31%BF.

geistjagerin, found a good article on female thigh fat here.  That gives theories for why thighs are particular problem areas for many women, and quotes Covert Bailey as reporting that, in his experience, for women "thighs usually slim down when total fat gets to about 18%".

18% is toward the high end of body fat percentage for female athletes, so may or may not be a desirable goal for you.  You could certainly get there without becoming an athlete, but you may or may not want an athlete's appearance overall.

emilym, the trick to giving such long and detailed replies is to avoid learning too much.  I simply repeat everything I know in every reply ;-)