About 15 years ago it was "discovered" that working in 60-70% of your THR would burn more fat than working out at a higher intensity. Basically you could still lose weight without completely busting your butt!
I want to explain what "the fat burning zone" and "cardio zone" is. So you can make the informed choice.
Now you have to know you are not going to lose weight while you are sleeping! So what's the deal with this fat burning zone?
You may be burning more fat as an energy source working out at 60-70% of your THR but is it the most effective way to lose weight?
We call working out at 70-80% of your THR the cardio zone because this is the intensity required to receive heart benefits.
The more active you become and the higher the intensity, the more carbs are being burned primarily as a fuel source. Less fat cells are being burned but more calories overall are expended. At relatively low intensities you burn 3-5 calories per/min. At higher intensities the rate of energy expenditure increases to 7-9 calories per/min.
Do The Math
If losing weight is a numbers game where you want a calorie deficit, you want to eat less and burn more.
If energy is work and work = force x distance it's pretty simple to say that the harder and longer you work out the more calories you will burn.
Our case study is 130lbs, who is walking/jogging to lose weight.
walking burns approx. 2.4 cal/hr/per lb
Jogging burns approx. 4.2 cal/hr/per lb
For an hour of walking she burns 144 calories
For an hour of jogging she burns 546 calories
Just that simple comparison shows how much of a difference a higher intensity makes!When people ask me about what zone to work out in, I tell them to do what they can. Ideally you always want to challenge yourself. You WANT to work out hard to get the most out of your work out.
For a beginner the fat burning (or weight maintenance zone) for a longer duration will be beneficial to them because beginners will lose weight as long as they are doing something. If being able to work out at an easy intensity gets them in to the gym then GREAT! Besides, they can always look forward to increasing intensity in the future. As long as they try to complete 20 minutes a week at a more challenging intensity for heart benefits then they are on the right track.
If someone with more experience asks me about what zone to train in for weight loss I highly suggest they work on increasing intensity before increasing duration. To put an avid runner down to the fat burning zone is retrogressive.
For people trying to gain weight I understand that putting on mass in a healthy way is hard and you want to do cardio to get rid of that unsightly fat layer, without losing any hard earned gains. My recommendation is 20 minutes of high intensity twice week. Just enough cardio for burning calories and some heart benefits but not enough to burn off the protein bar!
Metabolism, heart rate and calorie burning is a complex subject with many different opinions. As usual, do your research and do what's right for you.