Calculating TDEE and exerices calories

CA_Underdog

MyFitnessPal's TDEE and Garmin's exercise calories for me are totally at odds with each other. Any simple tips for finding more accurate numbers, so I can figure out how much to eat back?

+ I tell MyFItnessPal I'm "sedentary", and Garmin I'm activity class 4/10.

MyFitnessPal suggests eating 2,030 kcal/day (excluding exercise) given my goal of losing 2lbs/week. Therefore, it believes my TDEE is (2030 + [3500x2/7]=) 3,030 kcal/day. To clarify, for every pound of fat you want to lose, you must eat 3500 fewer calories than you burn per week, or 500 fewer calories per day.

However, during an hour of light aerobic activity--my heart rate was at the top of zone 1 and I had a very light sweat--my Garmin Forerunner 110 with access to my heart rate says I burned 127 kcal.

These obviously disagree:

1. Consider if I were to exercise at this light intensity for 24 hours, Garmin says I'd burn 127 x 24 = 3,040 calories. That's about what MyFitnessPal says I burn just being sedentary.

2. Consider that MyFitnessPal believes I burn (3030/24=) 126 kcal per hour just being sedentary. Thus, by burning 127 kcal exercising, I've only burned one EXTRA calorie!

CA_Underdog

My Forerunner 110 must be at fault. My heat rate was dropping in and out at this low intensity. I figured it would be fairly accurate if it caught it "most" of the time, but I guess not.

MayoClinic says even at 200lbs, I would burn 305 calories/hr even walking 2mph:

http://www.mayoclinic.org/healthy-living/weight-loss/in-depth/exercise/art-20050999

And heart rate gel is the solution:

http://www.dcrainmaker.com/2010/04/troubleshooting-your-heart-rate.html