HRM and fitness vs fat burn

Dad_of_3

I got on the treadmill last night. This was my first walk with the HRM on. I typically walk 3.5 mph, but I quickly learned this walking speed puts my heart rate in the fitness range. I had to slow the pae down to 1.1 mph to get my heart rate in the fat burning range.

I walked 30 minutes in fat burning mode (for 320 calories). I bumped it up to 3.5 for 10 more minutes so I could feel like I actually did a little something worthwhile.

At my weight (more than 300), although my normal pace is hitting the fitness range, does it really matter if I go slower for a fat burn vs faster for a fitness burn?