Is it better to run or walk fast to burn fat?

I have read different takes on this question.

My belief is that consistant exercise is the key to changing your body (inches lost vs lbs are way more important).

Find what you enjoy and stick with it and you will see your body change.

Hiyah, Dustin

The answer is pretty much "yes". It's best to do both, variety keeps the body guessing and it keeps you from becoming bored. The research, however, tends to favour higher intensity exercise for greater fat burning.

Here's a cut and paste of some information that explains all the details. [from http://www.fitstep.com/Library/Info...o_fitness1.htm]

The Low Intensity = Fat Loss Myth

It is a myth that low intensity is best for fat loss just because more fat is burned for fuel as a percentage of the total calories burned.

Low Intensity (L.I. for short) burns about 50% fat for fuel while High Intensity (H.I.) burns about 40%. This is not a big difference.

Say, for example, you burn 100 calories in 20 minutes of L.I. work compared to 160 calories in 10 minutes of HI work, you've still burned more total fat doing HI.

High intensity training will also boost your metabolism long AFTER the workout is done. This does not happen with low intensity training.

High Intensity training is a powerful fat loss tool, but should only be used by trainers who already have a good level of fitness.

The basic idea when you're trying to lose fat is to create a caloric deficit. The type of training does not matter so much as creating that deficit. High Intensity training just creates the deficit more efficiently than Low Intensity training.

All this being said, it's better to do something than nothing, and it's better to do that which you enjoy as it's more likely you'll continue on with it.

In your quest to banish fat don't forget that weight lifting is a tool you should consider adding to your repetoire - lean muscle burns fat long after you're done working out.

Cheers,
Nat

NAT IS BACK!!! Picture Lisa doing her happy dance!!!

Yeah, wow, I did a double take when I saw that name! How HAVE you been mah lady? *Angela does a gentelmen's bow*

Been travelling, lifting, leaving us all to fend for ourselves?

Nice to see your buffalos.

how often is it okay to do HIIT without cutting into your muscle mass?

Dustin,

Nat does an excellent job in her summary...I totally agree. I would still like to expand a bit on it.

In the sense that we want to control the amounts and types of carbs we eat, no matter what plan we subscibe to, there is an advantage towards progressing in the ability to do higher and higher intensity workouts to improve our aerobic capabilities and thus increase the upper limits of our aerobic threshold. The higher that threshold is, the harder you can work and still metabolize fat at a rate where you can sustain your workout for longer periods of time without needing extra carbs to support the effort and/or recovery. At the same time, as you train your body towards the higher aerobic threshold, even if you don't go over it, your body will be able to metabolize fat stores to replace the more quickly used energy stores of blood sugar and glycogen at a faster rate and thus you will recover faster to do it all again. :-)

It is a balanceing act. Those that practice short, high intensity activities (like 30 - 60 minutes of cardio) have different needs then those that that do long, moderate-hard activities (like 5 hours on a bike). The previous might need to find ways to fuel up a bit in order to recover while the later needs to fuel up during and after to both sustain their efforts and recover afterwards. Of course, there are the spectrums in between.

The bottom line is that in conjunction with the bare facts of maintaining a calorie deficit in order to loose weight, if we train our bodies to be able to use fat reserves more efficiently to higher intensities, we can work harder and/or longer to burn more calories without upping carbs much and still comfortably maintain control over our WOE.

HOWEVER...all that being said, CARBS, like calories are not the enemy in and of themselves. It is the excess and quality of both carbs and calories that are.

Joe, OK, this is one of those questions that for years I thought was interesting but never really cared about. In my way of thinking, I think that if one is eating in a nutritionally sound way and sufficiently enough food to sustaing both activity and recovery that "cutting muscle mass" does not occur in the strictest sense. If the question boils down to trading off heavy weight training for HIIT and thus limiting muscle development, I don't really know. Keep in mind that we don't add muscle cells after we mature. In fact, we loose cells but we develope those we keep to be stronger and in that process we increase their mass. (Sort of like brain cells, we only kill them. LOL) Now, I do not body build for the sake of body building. My activities are centered around cycling and thus "excessive" muscle mass in the upper body is not my goal. Carry an extra 10 lbs (or more) over a big hill and you will know what I mean. LOL

So...after reading the first part of my response, maybe I am talking out of my area of comfort and/or knowledge but I am interested if others contribute.

Hiyah Cue Bald 1

I'm in complete agreement on the carb issue - they aren't evil, just as LCing has taught us fat is not the enemy - it's a matter of choosing the right carbs.

Your statement about losing muscle cells and not replacing them has me a little confused though. Do you have any articles or pub med journal entries you can share on this topic? I'd be very interested in reading them!

From the research I've done when we workout to increase the mass of our existing muscle fibers (be they type I or type II) we are engaged in hypertrophy. There is, however, another type of growth, called Hyperplasia - which refers to an increase in the number of cells or fibers.

Hyperplasia is harder to measure in humans, but studies show that it does seem to happen (it happens in animals and similar tests produce similar results in humans).

There are two ways that hyperplasia happens. First, large fibers can split into two or more smaller fibers (i.e., fiber splitting). Second satellite cells can be activated.

Satellite cells are myogenic stem cells which are involved in skeletal muscle regeneration. When you injure, stretch, or severely exercise a muscle fiber, satellite cells are activated. Satellite cells proliferate (i.e., undergo mitosis or cell division) and give rise to new myoblastic cells (i.e., immature muscle cells). These new myoblastic cells can either fuse with an existing muscle fiber causing that fiber to get bigger (i.e., hypertrophy) or these myoblastic cells can fuse with each other to form a new fiber (i.e., hyperplasia). Hyperplasia is painful - I've gone there a few times myself - it's beyond failure (i.e., being unable to walk after a lowerbody workout for a few days, not just that 'ouch, I worked those quads big time feeling').

There is also evidence that depending upon the type of exercise you do you can actually change the ratio of types of muscle fibers that comprise your muscles. There are two main types of fibers in your muscles.

Slow Twitch: These are also known as Type I muscle fibers. They are responsible for long-duration, low-intensity activity such as walking or any other aerobic activity. They have lots of mitochondria and burn mainly fat - not lactic acid.

Fast Twitch: These are known as Type II fibers (they are divided further into Types IIA and IIB). They are responsible for short duration, high intensity activity. Type IIB fibers are built for explosive, very short-duration activity such as Olympic lifts and contain no mitochondria. Type IIA fibers are designed for more moderate-duration, high-intensity work such as weight training - these contain limited mitochondria but not as many as Slow Twitch Type I fibers.

Endurance training favorably modifies the capillarization of skeletal muscle. Some research findings actually suggest that specific training (or inactivity) may actually induce an actual conversion of type I to type II fibers (or vice versa). So while the characteristics of fiber-type distribution are determined largely by genetic code, it does appear that some transformation is possible in muscle fiber type with chronic and specific types of physical activities

You actually touched on this in your comments about increasing your anaerobic threshold. With training and consequent adaptation to exercise stress, the nature of the slow-twitch fibers changes. There is an increase in the capillarization within the muscle fiber bundles as well as the number of mitochondria in each fiber.

Enhancement of the oxidative capacity of fast-twitch fibers with endurance training brings them to a level at which they are almost as well equipped for oxidative metabolism as the slow-twitch fibers of untrained subjects.

Sorry, I'm starting to babble now

You can read more about Hyperplasia at: http://www.afpafitness.com/articles/FiberType.htm

Joe, to take a stab at your question - Too much HIIT would be dependent upon your physiology, I would think. Generally it's recommended you do no more than 2 or 3 sessions a week. HIIT is muscle sparing vs. longer slower cardio and it raises metabolism. It's also hard - I don't think you'd want to do more than that!

Nat, of the longwinded this morning.

Just a quick, trivial sidenote: we do actually grow new brain cells. The losing brain cells theory (except in the case of physiological trauma, of course), which never made a whole lot of sense to me anyway, has in recent years been disproven.

So don't worry, your brain will be alive and kicking for many years to come!

P.S. Here's one article I found with a quick search. It's not the one I read, but it has similar conclusions.
http://www.princeton.edu/pr/news/99/q4/1014-brain.htm

NAT & Alopex....THANK YOU, THANK YOU, THANK YOU. I are now more educated then always thought I was. LOL Seriously, some great info to correct my mis-information...I *HATE* being W-R-O-N-G!

Thanks!

I prefer to think of it as being 'more educated than before' - you weren't w-r-o-n-g, you just had some older info!

Alopex, great find - lovin the new ideas and the science behind it all!

-Nat

Hi all! I'm glad you liked the information.

That brain cells thing always bothered me, even when it was first taught to me in high school biology. So I argued with the teacher ("that CAN'T be true!") and lost, of course, because I had nothing but my gut to go on. I felt so gratified when the scientific community decided to agree with me.

At the time, I decided that science 50 years from now is probably going to make what we think we know now look like kindergarten, and we're all going to feel dumb for believing what we've been taught. But it isn't our fault we trust contemporary science, 'cause it's all we've got.

There's nothing wrong with being wrong (which is actually just "misinformed") when you don't have all the facts!

(And holy cow, Nat, you sure know a lot about muscles! )

I'm learning, Alopex ! You know the old saying "You always want what you haven't got"? Well the first step for me to getting what I wanted was a lot of reading and researching. I'm just happy it's of interest to others!

Cheers,
N