cardio vs. weight loss zones

what is the difference? 

for instance, if i do an elliptical for 30 minutes and my heartrate is in the "cardio" zone rather than the weight loss zone, am i really not going to lose weight?

Might want to check out this link:  here

What is the difference between the two zones?  My heart rate monitor has calories burned and fat % calculated and I know it gives a higher fat % (60%)when my heart rate is in the slower zone and when I get my heart rate to the hard zone the % is only 40% and its 50% in the moderate zone.  So if I do the elliptical for 30 minutes I might burn more calories in the hard zone but less of those are going to be fat.  So its kind of a wash - I mean I might burn 300 cals at lthe low zone and 150 of those fat  but working in the hard zone burn 500 but  200 would be fat based on 40%. 

I don't know anything about "zones", but if your heart rate is up during ANY kind of exercise, that's a good thing!!!

The difference are these:

weightloss zone = low intensity cardio

cardio zone = high intensity cardio

weightloss zone cardio burns less calories over all because you are doing less over a long period of time, but it primarily burns fat for fuel. Cardio zone cardio starts off primarily burning glycogen (sugar)in the muscles and the liver, but over all burns more calories.

When it comes to "weightloss" cardio zone does the trick faster because you burn more calories over all. I can walk for an hour and burn 522 cal or I can run-jog and burn well over 800cal.

But - let's say my muscles use 1 gram of fatty acids to aerobically produce ATP - that's a 9 calorie gram.  Or, they could use 1 gram of glucose to anaerobically produce ATP - that's a 4 calorie gram.  I'm still learning and figuring this out, but I believe that is why the 'weight loss' zone is touted.  We all know gram for gram that fat has a higher calorie content than carbs, so it would seem ideal for weight loss to have the body burn off fat during exercise. 

As it's true that gram for gram fat is higher calorically, fat grams ultimately are not the culprit. It still boils down to calories in vs calories out. Even when we talk about bodytypes (endomorphs, ectomorphs, mesomorphs) it still boils down to calories in vs calorie expenditure.