Question about heart rate during exercise...

Hello everyone :)  I usually hang out on the vsg forum, but I came here in hopes of getting answers to a question that I have about target heart rates.

Why is it that my heart rate monitor is telling me that I need to be in a lower heart rate range to burn fat than to improve fitness?  Isn't that why we're burning the fat.... to improve fitness? 

And more importantly, should I be following the guidelines that the hrm came up with for burning fat?  I don't feel like I'd make very much progress towards burning calories and losing weight if I do little enough to keep my heart rate in that lower range. 

And I am terrible with science, so if someone could explain this to me in the simplest terms possible, I would be ever so grateful. 

Thanks! :)

 I'm afraid I am going to mangle this, but will try because it looks like you haven't gotten any responses.  My understanding is that your body burns different types of fuel (glycogen from liver, fat) based on the perceived level of exertion, and that lower levels of exertion for extended times are better for fat burning.  For me, there is value in also doing those higher levels of exertion because they cause changes in muscles and cardiovascular system that are also awesome for your heath.  You could consult with a trainer about the best balance between those two kind-of-different goals.

There are two different systems your body utilizes while exercising... Aerobic and anaerobic. In your aerobic zones, also referred to as the "Fat Burning zones", your body uses it's fat stores for fuel. When you are in your Anaerobic Zones... Typically levels 8-10 on the scale of RPE Jenny above was referring to, you are in your Anaerobic zones where your body is burning it's stored sugars (Glycogen) for fuel, which can and does get depleted very quickly. The best way to improve cardiovascular fitness and spike your metabolism is to create a solid BASE in your lower aerobic zones. So slowing down is your best bet for weight loss. To improve performance, you definitely need to increase your AT (Anaerobic Threshold) over time as well. My guess is that your HRM is set to help with fat burning / weight loss. As for target HR zones, to get the true answer to that question, I recommend you get a VO2 Max test. Most colleges and many performance centers offer these tests for a couple hundred dollars. Best of luck... Hope this helps...

 Awesome answer, thanks for the save.  Is that you on the bike?  I'm trying to get over the fact that all my biking partners are riding the STP (Seattle-to-Portland) on Saturday and I'm not.  I just didn't feel ready for 200 miles in one day.  I'm planning on the RSVP next year, though (Ride from Seattle to Vancouver and Party).

Thank you both for responding! That explains things much better. And sorry it took me so long to respond; I seldom come to this part of the site, and after no one responded for a day or two, I sort of assumed I wasn't going to get a response and forgot to check back.

Thanks again!