Interval training vs Steady State; Fat Burning Zones

Good evening peeps. It's me, your "friendly" neighborhood bodybuilder who likes to not only be thorough but also get under everyone's skin. I'm the guy that keeps up with MOST of my friends regarding their diet & training. I may not critique them all the time, but I see things. (No I don't see dead people) I watch my friend's progress. I know who's 110% dedicated to making their transformation goals happen and who isn't and does things half *kitten*.

Anyways, the purpose of this newly created thread is for me to talk about CARDIO and how it holds it's place in your training and fat loss project. However, before I get started I want to talk about this "fat burning zone myth" people so quickly call it. The problem isn't whether or not the Fat Burning Zone is a myth, it's that people too often confuse percentages with absolutes.

As you move from low intensity cardio to high intensity the amount of fat vs carbs burned shifts from one to the other.

At low intensities, you MAY burn 100% fat.
At high intensities (or anything above the lactate threshold), you MAY burn 100% carbs.
At any intensity between, you MAY burn a portion between the two.

If you're walking at 3mph, and burning 5cals/min but you're burning 100% fat. That's 5cal/min of fat.
If you're running at 6mph, and burning 10cals/min but burning 50% fat.

People are thinking, but that's burning LESS fat? No it's not.

10 cal/min * 50% = 5 cal/min of fat

It's the same amount of fat in absolute terms although it's a lower percentage. But you're also burning 5 cal/min of carbohydrates. We'll also say that at 6 mph you're burning 10 cal/min but still 65% fat. That's still lower by percentages than at 3mph, but you're burning 6.5 cal/min of fat which is higher. Also you burn more TOTAL calories as well as depleting some of the carbs in your muscle.

When you're depleting muscle glycogen whether it's by exercise or carb restriction, you body will increase fat oxidation by ten-fold. Also it matters MORE what you burn the rest of the day versus what is burned during exercise and this is ESPECIALLY important for INTERVAL training.

This is more the reason for doing Interval Training (HIIT) in the first place because:

1. When doing interval training, your body burns MORE later on in the day.
2. When you eat carbs they tend to go more toward refilling muscle glycogen versus being used for energy.

To summarize:

Low intensity cardio = More direct fat burning effect as it burns fat for fuel but you don't get anything else out of it.

High intensity cardio = Burns a portion of fat + carbs and impacts greatly on what you burn later in the day.

Interval training = Burns only carbs during the actual interval training, but also depletes glycogen amazingly and HUGELY impacts what you burn later on in the day.

Also think of it this way:

A quick 5 minute (15 sec on / 45 sec off) HIIT training session causes fat to MOBILIZE from the fat cells.

A complete 5 minute rest causes fat transporting into the bloodstream to prep for oxidation

Steady state for 20-40 mins (120-140HR) causes direct FAT OXIDATION to take place since it's a DIRECT fat burner.

This is the simplest way of explaining it to people so they understand. If you have any questions, let me know. Also keep in mind that if you are incredibly obese then it doesn't matter AS MUCH as it does for people who are somewhat lean and are trying to get even leaner or better body composition.

Edit: I also want to remind everyone that NONE of this matters if you're not in a deficit and your diet isn't spot on. Just saying.