It depends. Some people have naturally low heart rates, especially if they are athletic and fit, as you certainly seem to be. If your heart rate is constantly low and you don't experience any negative symptoms to go along with it, then you're just one of those lucky people with a laid-back heart! However, if you experience sudden changes to your resting heart rate, along with other symptoms such as dizziness, difficulty breathing, and fatigue, then there could be something more going on. Especially if your heart rate gets into the 30s. The lowest mine ever gets is the 40s, and that's only on rare occasions, and when I'm really relaxed. I would suggest that you talk to your doctor and have him/her set you up with a 24-hour Holter monitor, if you haven't already. This will shed light on what your heart is really doing. If you've had no symptoms with a low heart rate for several months, then the ones you're recently experiencing are quite possibly unrelated to your heart. I for one am betting you're OK. Do get checked out, though. It's always, always best to be sure. Best of luck to you!!
Your heart rate is slow, but it seems like you have an extremely active and good lifestyle with lots of exercise.
It's really reassuring that your heart rate increases to 165 bpm (though this is a bit lower than expected, you are at my age and I can get up to over 200 bpm, but there are certainly variances in peoples max heart rate (as well as resting heart rate).
An example: My dad is always at 45 bpm sitting down, and in the 60s when moving around, and he is not very fit. My mom exercise 4 times a week and her resting heart rate is in the 70s.
I think this is just how you are, and also a result of your healthy lifestyle, but I would see a doctor about the tiredness (and get an opinion on the heart rate from him).
Very good answer from the previous poster, by the way.
Thank you both for your help. I think that the fatigue and the low heart rate are most likely unrelated, I'm probably just looking for something to be wrong. I don't know if my heart rate actually goes above 165 if I workout harder, I just observed during what seemed like moderate effort it got up to 165. I think the low heart rate only freaks me out because when I was 100 pounds heavier my resting heart rate was always higher than 100 bpm, and I don't really consider myself a "well conditioned athlete". I only started exercising a year ago and just do 45 minutes of moderate effort on an elliptical machine. I'm not a marathon runner or anything. At any rate, thank you for your taking the time to respond.
I think you're right. So many factors can affect the heart rate and freak us out for no reason. In your case, it sounds like you should be celebrating! Losing that much weight is an amazing achievement, and you should be super proud!! Congratulations! I bet that your heart is healthier than ever.