It is normal for your weight to act the way it has. To break it down in a simple manner, there are two sources for energy, protein and fat. If you are not getting enough protein then your body will store fat. If your protein level are high enough then your body will not store fat. (Storing fat and burning fat are two different subjects.) Be careful in increasing your protein. Too much and you won't be able to "go-number-two" (to say it politely). That's why it's recommended to take fiber when your diet increases the protein amount. Now for the plateaus. when you loose weight your body will drop pounds at first then stop. This is a normal process that allows the body to check why it's loosing weight. Maintain the diet and when your body has caught up to itself then you will start loosing weight again. The simple formula of More calories burnt than taken in plays a huge role in this factor. Exercise and watch your calories and you should be fine. Good luck and take care.

I can only really make suggestions from the workout end, but I think what others have said about starvation mode is useful.

Once your body gets used to a workout routine, you will hit a plateau.  What that means is that in order to lose more weight, you'll have to do more intense workouts and more of them, while ramping up your caloric intake a bit.  So if you're exercising 3-4 times a week, try exercising 5-6 days a week, or going for longer than an hour, or increasing intensity (e.g. if you run an 11 minute mile, run a 10 minute mile, or if you only run for half a mile at a time, run 3/4 mile at a time).  Once an exercise becomes easy for you (or easier), your body starts to adjust.

Also, one of the things conspicuously missing from your workout routine is weight training.  Though cardio is best for losing weight, it's the anaerobic workout you get from weight training that increases your metabolism.  Try making the first half of your workout routine weight training.  This will ramp up your metabolism temporarily before you start your cardio, making you burn calories more efficiently.  Remember, however, that weight training can cause you to gain muscle mass, which may result in temporary weight gain, so don't be discouraged if it takes a few weeks to start working.

Your metabolism relates directly to your oxygen intake.  Cardio helps burn calories by *temporarily* speeding up your metabolism, but to raise your metabolism over the long term you NEED to include strength training in your workout.  You also NEED to drink enough water.  If you're not drinking your full 8 glasses/day (more when you have heavy cardio workouts), you're not getting enough water and this can slow down your metabolism and cause you to retain weight. 

Finally, it's not just what you eat, it's how you eat it.  Your metabolism slows down when you sleep, so dinner should be a light meal - eat most of your calories in breakfast and lunch - and you should eat dinner about 4 hours before you go to bed.  No late-night snacks (this is my personal weakness!!).  Also, if you plan out your food for the day ahead of time, you can break meals into smaller parts and eat much smaller meals throughout the day, rather than three large meals.  So for instance, my normal breakfast is a banana and Kashi GoLean! Crunch.  Since I can take the banana with me, I try to eat the cereal at 7 before I go in to work and the banana around 9:30.  If you can do this with all your meals (make sure you portion them out beforehand so you're not just eating six big meals), your body will break down foods more efficiently and your metabolism will speed up.

I hope all this helps!

First off, you need to see your doctor ASAP.  He needs to do some tests on you to check for hormonal and nutritional imbalances and few other things that could cause your scale to "stick" for so long.  The dorks at your diet center should have sent you there ages ago. 

I calculate your BMR at 1600.  Eating only 1200 gives you an automatic deficit of 400 PLUS any exercise you're doing. Even without working out, eating 1600 calories a day should result in just over half a pound a week of weight loss.  At fully sedentary, I calculate your RMR at 1930.  Eating 1500 is still below your BMR.  Try eating 1600 and try doing it for at least 6 weeks.

How many weeks were you only eating 1200 calories?  That's probably how long you'll need to eat more in order to get your metabolism restarted.

I'd also say that you should try changing what you to do to work out.  If you've been doing aerobics, get on the elliptical.  If you've been doing the elliptical, start a spin class.  Lift some weights - free weights.  Try yoga and pilates.  Take up a new sport.  Start swimming. 

The reality?

You're different than I am. Or anyone else on this board, so everything ANYONE says is only a perceived guideline for what works for them.

And I have to disagree about late-night calories: they won't change your metabolism or magically count more than calories eaten during the day. The real problem with late night calories is that naysayers aren't thinking about them as someone who eats a healthy dinner that fits the parameters of their designated caloric intake at 9pm---it's the late night crap binging, the snacking that adds up to unnecessary calories. Sort of like lack of sleep. It's been widely stated that we insomniacs have trouble losing weight, which I clung to as a great excuse for why my own body is changing at turtle pace regardless of my hard work---but no, sorry (and tell me I wasn't bummed to learn the reason as I was hoping for an aha moment)---the REASON is because lack of sleep makes you grumpy, disoriented, and less likely to make good choices. Lack of sleep doesn't magically add fat, just like intake of calories after x o'clock doesn't either. It's all about the choices. Alcohol WILL add calories BUT many times it's about the food choices one makes after a couple of drinks than the drinks themselves.

I'm no expert, trust me. I've eaten more, eaten less, added weights, upped or lessened my cardio---and it's not working. BUT I do know that all of us have to keep juggling different healthy habits until we put the puzzle together. Not one singular person can pinpoint your perfect diet, even a doctor. The sad truth is that some of us don't fit the "it's science, dummy" partyline that many give out about weight loss. I had bloodwork done 3 weeks ago that I'm STILL waiting on the results of (yay healthcare system!)---but the reality is that it may show nothing at all and I'm stuck with this snail's pace. Sucks, but it is what it is.

When you're looking in the mirror or at the scale, it's no consolation, but know that you ARE making extraordinary choices and changes on the inside.

I'll keep trying if you do.

I have no advice except to tell you about me.

I lost 45 lbs over over about 20 weeks, going from 317 to 272, then it just stopped. I was eating the same , exercising a little more as I started biking to work everyday, and BLAM I hit a weight-loss wall. I lost nothing for about 5 weeks. It was terrible....and what did NOT help was listening to know-it-all know-nothings who said I was eating too little, too much, needed to exercise more or differently, needed to drink cider vinegar, whatever. People who said it's not physically possible to NOT lose weight with a 1000 calorie deficit, and made me feel stupid and like a failure. I ignored all that, stuck it out, and eventually it broke. I am now down 10 more lbs, though they seem to be coming off slower and more inconsistently than before. My body clearly just needed a break...a plateau after losing around 10% of your body weight is quite common, I have read...and started up again on it's own time.

The human body is amazing, complex, and very responsive. It does not follow math...I used to be all about the math and science of weight loss but now I am realizing it's much more complex than that. Just do your job of eating well, keeping exercise in your life, and making sure you are eating around what a person of your height, weight, sex and age should be averaging to lose 1-2 lbs per week, and eventually it will happen. Hm turns out I did have some advice lol

Water.

How much are you drinking? Try drinking more. Lots more. Burning fat causes the fat-soluble toxins that build up in your fat cells to be released into your blood. If you don't get it out of your system it can clog up your metabolism.

The oft-quoted 8 glasses/day is fine for people who aren't dieting, but you need to get more fluid than that to deal with the toxins.  It doesn't all have to be pure liquid water either; anything with water in it counts.

I agree with Melkor to a point.  Having been stuck hard as long as she's been there tells me that she ought to see the doctor and be checked for any number of things.  My suspicion is that there is a vitamin or mineral deficiency.  Many of these things (Vitamin D, for example) can impact weight loss.   

She's been on a very restricted diet for quite some time and, as everyone here on CC is aware, eating under 1200 calories is something that should be supervised by a physican *because* it's almost impossible for a lay person to get a properly balanced diet. She's been hovering right around the border of it.  Taking vitamins doesn't always = usable vitamins in your body. 

Sheesh, she's female.  We gain and loose water.  I've dropped nearly 4 "pounds" this week and most of it is water weight.  I'm finally to a point that my fingers don't look like sausages any more.  You'd think that there would be *some* variance over that many weeks. 

WOW! This pot is seriously stirred! I can tell you only my personal experience. I only lost 20 pounds which was slightly more than I wanted to. I ate under 700 calories a day making sure I scored an "A" every day, I did that for two weeks. Then I gradually increased thecalories to 900 for 2 more weeks. At that point I gradually increased the calories to 1200 and stayed there until I was a little below my target weight. At the same time I paid careful attention to what I put in my mouth to make sure I was getting enough protein and vitamins. don't get fooled into thinking that you can replace the vitamins you get from your food with a bottled kind. There is a lot more to it than that. I felt great, had lots of energy, clear head, my skin improved. More water was important. I don't care for it much and I tend to forget. Now that said, please keep in mind that I am 50, 5'7" and was only 15 pounds "overweight" I got down to 140 and was thrilled. So this argument you are having over the body going into "starvation mode" comes down to, I think, every body is different and responds to food differently. I ate a lot of leafy greens and lean meat...oatmeal or 2 eggs for breakfast, salad with carcass on it for lunch a regular supper...I say regular not in the American sense, healthy portions. At one point I did stop losing for a few day so I ate a piece of chocolate...one piece, not a burger, fries and double scoop ice cream and prob coincidence but I started losing again. I think the most important thing for me is portion control. If we don't change our eating habitswe are going to gain it all back again and go through this whole process again. One more thought, when you get there beware! I met a man who eats constantly but he is really on the go 12 hours a day so he burns it up. We got married. It took me over 2 years but I have slowly put it back on...that's why I am here! lol I am at 700 calories for the next 2 weeks...lots of Swiss Chard!

Keep at it, never, ever give up  Good Luck!

I can tell you my experiences of losing weight starting at 33 years old, 5'5", 187 (not so far from your stats, is it?).  I started eating 1200 calories a day.  I lost about 10 pounds over the course of a month.  Then I kicked up my exercise and did not eat any more.  Oddly enough, I did not lose any weight.  I finally posted about it and got people telling me to eat more.  By increasing my calories to 1500, I lost another 10 pounds.  Inadvertently I ended up doing the same thing again.  I was having so much fun with my exercise that I was overdoing it.  I had to increase my calorie intake to 1800 to lose anymore.  I'm now sitting in the middle of the 150s trying to decide if I really want to track my calories and exercise again or just maintain my status quo.  I wear a size 4-6 so from that point of view I'm quite content.  I'm eating roughly 2000-3000 calorie a day depending on my exercise level and I've maintained my weight for the last 6 months.

Definitely increase your calories.  Make sure you're getting enough water.  Make sure you're getting enough lean protein, whole grains, fruits, and vegetables.  Make sure you're getting enough exercise.

"I'm now sitting in the middle of the 150s trying to decide if I really want to track my calories and exercise again or just maintain my status quo.  I wear a size 4-6"

Wow I'm really impressed with you. Mid 150's and in a size 4-6. You must be proportioned REALLY well, you go girl. I wouldn't lose anymore if I could fit in a size 4 at mid 150. I'm 5'5" as well and don't get in a size 4 until 130 - mid 120's.