Heart rate monitor

I bought a monitor and figured out my maxiumn heart rate is 158.  (I am 62.)  At what percent of my max heart rate do I start to burn fat?  My resting heart rate is 62 (same as age.)  I take spinning classes 5 days a week, and walk 2 miles a day for 5 days a week at fairly fast pace--I can still carry on a conversation with walking friend.   Also I work out with weights 2 to 3 times a week. Patricia 5'1" 262/130 I struggle with weight gain on a daily bases RNY 3/11/2005 

I don't know anyway to figure this out without having it measured. I had mine measured at my gym as part of my personal training package. They gave me a print out of my heart rate zones and the percentage of fat vs. glucose burn that occurs for my body in each of those zones. I would imagine that most gyms do this, but I had mine done at a Lifetime Fitness location.

Here's an article written by Jeremy Gentles that you might find useful. Becky http://www.obesityhelp.com/forums/fitness/cmsID,2277/mode,co ntent/