Burning 5000 calories/day!!!!

Okay, well first of all, you may want to get your body fat percentage tested. If you are 160 pounds and very muscular, you may not NEED to lose any weight, or very little anyway. What makes you think you need to lose weight? Because of the number on the scale or because of fat you have?

The other thing is that you may not be eating enough. As counterintuitive as it sounds, if you are truly burning 5000 calories in a day and you're only eating 1400, your body is not getting NEARLY the energy it needs to perform its tasks, and may be slowing down your metabolism as much as is possible. You should probably consult a nutritionist who can use calipers to test your body fat percentage and advise you on how much weight you need to lose.

I use a Polar HRM as well, I have been told it is not a reliable source to calculate your calorie burn for such a long period of time, aside from exercise, and if you want to track your calorie burn on a daily basis, it's best to use a bodybug or something similar that is meant for that purpose. Just thought I would pass that along to you, hope you find the answers you're looking for!

Dang, you should be an Olympian.

I think the problem may be in your exercising. You said you're running 6x a week for 90 minutes and do strength training right after such a long cardio session. I have always been advised not to do strength training and cardio back to back. Ideally there should be a few hours of rest in between the two different types of training if you must do them on the same day. Why not back to back? Because if you're doing good strenuous cardio, you wont have the energy and power to give it your all in a strength training workout. Your body needs time to rest and recover. Recovery is mandatory to prevent injury and for your body to repair itself for the next punishing workout.
Also have you tried HIIT or interval training instead of long distance running? HIIT makes for an amazing workout and is totally controlled by your own will power. If you're not familiar with interval training you can easily look it up as there are tons of articles on it. If I were you, I would do the HIIT training about 4x a week and strength train 3x a week preferably on separate days. Do NOT do HIIT and strength back to back.
Lastly, eat eat eat. You're not eating enough for the amount of exercising you're doing. You should be getting around 1800 on heavy workout days. Adding more calories to your diet may sound counterproductive, but it will help you in the long run. Don't be afraid of carbs either, they are your friend. Get good carbs in from whole grains and vegetables. You want to try to get carbs and protein in with each small meal throughout the day; but keep carbs low after 7pm.
I hope this helps you. I sympathize with how you feel about working out so much and not having the scale budge. I am in a similar situation. I'm 5'5" 139 23% body fat. I didn't start losing weight until I added more calories and especially more carbs. (I try to get at least 200g on heavy workout days) You just have to keep your eyes on the prize and never give up. Keep in mind that changing and trying new ideas and methods of working out is the best way to find what will make you your most successful and give you the body you desire.

So to recap...you've lost 12 pounds in 3 months which sounds about perfect. You're lifting so you've probably put on some muscle too and you're doing cardio like a mad fiend. LOL. So there really are only two explanations...one, you're eating more than 1400/cal. day (which by the sounds of your workouts...is not bad because you're a fricking rockstar) and two, your hrm is off. I have a Polar too and love it. Haven't tried to wear it all day but it would be a good experiment. I'm guessing you shouldn't worry too much though. Take body measurements with a measuring tape (on days when you didn't workout the day before) and track those too. My guess is you're trimming off body fat and building muscle which is why your aren't losing more. Just keep it up and track the next 12 weeks of measurements and see where you stand. My guess is you'll be 6-8 lbs lighter and start seeing more definition since you're building so much. I'd love to have your problem. Good luck.

Like others have said, I've always understood that HRM's arent for measuring calorie burn other than actually while you are exercising.

And given your stats and how much you are exercising, I think you are severely under eating. You'd probably loose more, have more energy & feel better if you ate more.

A couple of these posters have it exactly right -- your heart monitor is meant for use only during aerobic exercise. Wearing it during weight training or other non-aerobic periods (especially all day long), will give you dramatically distorted results. Avoiding a complicated explanation of why, suffice it to say that if you calculate your basic BMR so you know your daily caloric need without exercise, then add in any of the aerobic exercise calories from your HRM, then you'll know where need to be calorie wise. The rate at which you've been losing is good and reasonable. If you wish to keep losing about two pounds a week, just subtract 500 calories from what you need to maintain and exercise about 500 calories a day in addition to that.

You're doing it right -- you just got a freaky reading from using the HRM for something it's not intended to do. Use it only during aerobic exercise, and it'll all start straightening out.

Good work. Keep it up! The 90 minutes of running six days a week will be more than adequate to burn off the 3500 calories a week to eliminate one pound through exercise.

What she said.