Tuesday, March 1, 2011

Mythbusters: Fat Burning Zone

There are so many exercise myths but this seems to be the biggie and it leads to a lot of other myths, so I'll start with it.

The myth goes as follows: if you want to burn the most fat, you shouldn't work out intensely, you should work out in your "fat burning zone". How do you know what your fat burning zone is? Why just take 220 and subtract your age then multiply the results by .50 & .60!

That sound you hear all the way across the Internet is either me grinding my teeth down to tiny stubs or me screaming into a pillow so loudly, you can still hear it. Because this common bit of advice is so wrong on so many levels that it's hard to know where to begin.

Let's start with the whole "fat burning zone". Is there such a thing? Well, yes, but it's not a particularly big deal. The thing is, we burn a combination of fat, carbs and protein all the time. What varies is the percentage. So, yes, there is a training zone where the percentage of fat burned is the highest. But percentage isn't absolute calories.

The harder we work out, the more calories we burn. That means, at some point, even though the percentage of fat being burned might be lower, the absolute fat calories burned is higher. For example, if you burn 100 calories and 60% are burned from fat, that's 60 fat calories. But, if you burn 200 calories and 35% of them are fat, you've burned 70 calories from fat. The percentage is lower, but the absolute fat calories are higher.

Besides, even if you don't burn more calories from fat during the actual exercise, at the end of the day while we sleep, our body rebalances our energy stores. So any energy deficits are made up by burning stored fat. At the end of the day, if you burn more calories, you'll burn more fat. (Assuming you work out enough that you don't lose a lot of muscle mass instead. More on that later.)

The other issue with the whole fat burning zone is that most people have absolutely no idea what their real heart rate zones actually are. That 220 minus your age thing? Works for about five people. That's because it's kind of silly to think that every one who is 25 has the exact same maximum heart rate. Even on a team of 20-something athletes that were tested, the range of maximum heart rates varies from 160 to 220. That's an enormous range!

The difference means that, if someone with a very high maximum heart rate used the formula, they'd think they were working out in their fat burning zone when they weren't even close. The end result of both using the 220-your age formula and only working out in the supposed fat burning zone is that you are not burning very many calories so you're not burning much fat.
On top of that, this path can lead you down the path of losing muscle instead of fat. This is because muscles are a "use it or lose it" sort of thing. So, if you only work out in the fat burning zone (or lower because the formula is wrong for you) and you only do cardio because it burns the most fat, you end up losing weight slower and you lose a lot of muscle mass along with some fat.

So what is the way to lose the most fat? First, work out hard. Maybe not at maximum intensity every workout because that can burn you out and possibly cause injury, if you ramp up too fast. But don't deliberately hold yourself back thinking that's the way to maximize fat loss.

Second, don't just do cardio. You need to do some strength training and/or weight bearing exercises too. These will cause your muscles to work and that sends your body the message that it needs these muscles so they aren't available for fuel.

This is why running is such a great exercise for getting lean, by the way. It's both cardio and weight bearing at the same time. But it's not the only way to burn fat so don't worry if you hate to run.

Keep in mind that this advice is only to maximize fat loss. There are other reasons to exercise that would result in a different mixture of intensities and exercises being best. But for fat burning, hard cardio combined with strength training is the way to go. Piddling around at low intensities trying to stay in a range that might not even actually be your fat burning zone is not.

To read more about the Fat Burning Zone and your maximum heart rate, try these articles:

http://www.active.com/triathlon/Articles/The-Myth-of-the-Fat-burning-Zone.htm

http://en.wikipedia.org/wiki/Heart_rate
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