Sources Cited
(1) Frankenfield, D., Roth-Yousey, and C. Compher, Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults: A Systematic Review. J Am Diet Assoc., 2005. 105: p. 775-789)
FACT 2
Cardio in the "fat burning mode" is NOT efficient for overall fat loss !
Performing cardio in a very light intensity (within the fat burning range as indicated on most cardio machine interfaces) may burn off a higher percentage of fat per total calories, but the total calories burned is nowhere near the amount necessary to see efficient change in bodyfat levels.
Let's do the math.
Let's say you walk 3.0 MPH on the treadmill, placing you in the "fat burning" range,
but you only burn off 250 calories per hour. Your percentage of fat burned is 50%. That's only 125 calories of fat. If you did this every day for a week, you'd only burn off 875 calories of fat (of the 1750 burned total... to burn off 1 pound of fat, you need to burn off a total of 3500 calories). If you were to up that speed and jog at a 5.5 MPH, placing you in the "cardio range", you might burn off 600 calories in an hour. But only 20% came from fat. You'd still be burning off 120 calories from fat per workout or 700 per week (4200 calories total per week).. it is the overall number of calories burned that is most important.
Truth is, it is not the amount of fat you burn per workout that counts, it is the total calories burned and the caloric deficit you are in, that determines actual fat loss. And the higher the intensity your cardio is, the more you burn AFTER your workout. This is called the "afterburn". Higher intensity cardios can raise your metabolism for up to 24 hours after your cardio. Another reason why to up the intensity !
It has been recently shown that cardio intervals are more efficient in burning off overall bodyfat without sacrificing lean body mass. A 30 minute session consisting of 2 minutes of high intensity bursts followed by 1 to 2 minutes of low intensity recovery, burns off more fat overall due to the dramatic increase in the afterburn effect. This explains why sprinters have low body fat levels and higher lean body mass.
If you need a visual..... spend an hour on a piece of cardio equipment in the back of the cardio room. Which exercisers are leaner? The lazy treadmill walkers or the ones putting in more effort?