Burn More Fat during Cardio

http://runnersworld.com/home/0,1300,1-51-54-628,FF.html
Burn More Fat
by Owen Anderson, Ph.D.

Excerpt from the article:
"Many so-called "experts" recommend that the best way to burn more fat is to run slowly during workouts. You've probably heard advice about training in your "fat-burning zone," said to correspond to a heart rate of just 50 to 65 percent of maximum heart rate (MHR). This is equivalent to a running pace about 2 minutes per mile slower than your marathon race pace. In other words, very slow.

At first glance, such slow running seems like a great idea. A recent University of Texas study found that when athletes exercised at only 50 percent of their MHR, fat provided 90 percent of the calories burned. When the athletes sped up to 75 percent of MHR, fat provided "only" 60 percent of calories.

However, the higher-intensity session actually burned more total fat calories! This happened because the 50-percent workout burned only 7 calories per minute, while the 75-percent workout burned 14 calories per minute. A little simple math reveals that the harder workout consumed 8.4 fat calories per minute (60 percent of 14) versus just 6.3 fat calories (90 percent of 7) for the slow workout.

A study reported in last month's "Health Watch" column reached similar conclusions. In that intriguing experiment, world-famous fat researchers from Laval University in Quebec City, Quebec, reported that intense exercise led to a ninefold greater loss of body fat, per calorie burned, than less intense exercise. The scientists at Laval had earlier shown that vigorous exercisers are thinner than moderate exercisers who burn the same number of calories. From these studies, you might conclude that you should run at top speed to maximize your fat-burning potential. Not so. Above 85 percent of MHR, fat metabolism begins to drop. It appears that 75 to 85 percent of MHR is the ideal range for fat-burning.

Of course, if your current fitness doesn't permit you to run very far at 75 to 85 percent of MHR, you'll still reap weight-loss benefits if you do longer workouts at lower intensities.

HIT is the way to do it right!

Nice post reminds me to go do some cardio today .

glad to hear it

before everyone gets excited about this...

I think something needs to be pointed out about this study. At 50% MHR a person burns 90% fat. We are to expect the remaining 10% is either protein and or carbohydrate. At 75% MHR a person burns only 60% fat and the remaining 40% is either from protein and or carbs. What is interesting is that we as humans can only store about 3500 calories(roughly 1 pound) of carbohydrate as glycogen, which is ultimately our fuel source. Glycogen is only stored in our muscle and our liver.Protein and fat is converted into glycogen for energy which actually consumes roughly 23% of the calories in the conversion process. In cardio excercise we initially burn pure carb(in the form of glycogen, ultimately glucose) then the body switches over to burning stored fat as it is converted into glycogen. My point is this-since we are so defecient in storing carbohydrate, and the 75%MHR group burns 40% of its calories from a non-fat source then it should be understood that alot of the calories that are being burned ultimately come from protein storage-namely muscle tissue being broken down for energy.I believe it is important to look at where the percentage of calories comes from , not the total. And after cardio the metabolism is elevated for several hours, burning mostly fat. Perhaps low intensity excercise is the way to go.

nice post supersport

always good to get views from both sides

I am sure we will see many more views from both sides-the beauty of science is that it is ever changing...

Good stuff man, thanks SS.

Re: before everyone gets excited about this...

supersport said:

I think something needs to be pointed out about this study. At 50% MHR a person burns 90% fat. We are to expect the remaining 10% is either protein and or carbohydrate. At 75% MHR a person burns only 60% fat and the remaining 40% is either from protein and or carbs. What is interesting is that we as humans can only store about 3500 calories(roughly 1 pound) of carbohydrate as glycogen, which is ultimately our fuel source. Glycogen is only stored in our muscle and our liver.Protein and fat is converted into glycogen for energy which actually consumes roughly 23% of the calories in the conversion process. In cardio excercise we initially burn pure carb(in the form of glycogen, ultimately glucose) then the body switches over to burning stored fat as it is converted into glycogen. My point is this-since we are so defecient in storing carbohydrate, and the 75%MHR group burns 40% of its calories from a non-fat source then it should be understood that alot of the calories that are being burned ultimately come from protein storage-namely muscle tissue being broken down for energy.I believe it is important to look at where the percentage of calories comes from , not the total. And after cardio the metabolism is elevated for several hours, burning mostly fat. Perhaps low intensity excercise is the way to go.

Click to expand...

Supersport, Sorry Bro. Hate to bust your chops, but this is a bit off.

Protein and fat are NOT converted into glycogen. GLuconeogenesis (*glucose* production) can occur with protein, but not fat. Fat enters our metabolic pathways as fat (fatty acids), either after uptake from the blood or from w/ in the muscle cell (where they can be stored as muscle triglyveride).

THe 23% figure you mention is probably referring to the energy lost in oxidizing protein b/c the nitrogen-containing (amino) group cannot be used for fuel, but is instead lost as urea.

Protein oxidation account for < 10% of energy production during exercise, unless you've been exerciseing for hours on end (like 3+ hours) and / or are starving. This is true for low or high intensity. The pathways for simply cannot supply energy at a fast enough rate (roughly 1-2 kcal / min max.)

They used a *non-protein* respiratory exchange ratio to determine the % carbohydrate vs. fat oxidized in these studies. (This can be done b/c protein contributes so little to the fule mix.) This means that protein oxidation is so minimal that it is considered insignificant and is ignored.

The EPOC (excess post-exercise oxygen consumption) or post exercisie caloric burn is greater after high intensity vs. low intensity execise. Long duration, low intensity exercise does little for this. Go balls out for an hour or more, or do 20 maximal 1 min sprints and then we're talking about a meaningful EPOC. (Wt., training does it too.)

-Randy

Hey Randy,
Don't worry about busting my chops-it has happened before and I have thick skin....and this is part of learning, which is why we are all here.
Pardon my bust on the statement-protein and fat is converted into glycogen... I realize glycogen is only stored glucose. I was simply getting to far ahead of myself as I set out to question this study.
I should have stated that this was a study on marathon runners who typically run for 4-5 hours, and at this length of time at such a high HR and only 60% of calories from fat, there has got to be a drastic loss of protein. I thought this would be understood-that it was excercise for 4 or more hours. We simply do not have enough glycogen storage, and the study did not mention anything about consuming calories during excercise. And of course our max glycogen storage is 3500 cal, and I would expect that the typical long distance marathoner has less muscle to store glycogen. We have the majority of our glycogen stored in muscle as opposed to our liver, and besides which our muscle glycogen is not ready to be burned as fuel as it still has a process to go through. So I am thinking that the typical marathoner has probably 2000 calories of glycogen available for fuel(I could be mistaken here-just a guess).
I just believe for a BB or strength athlete that any form of excercise that burns a higher percentage of fat and spares more protein and/or carb would be more beneficial. An endurance athlete probably does not care about loss of protein as this could just be more body weight to haul around. A bigger muscle (or person for that matter) gets tired faster than a smaller muscle (or person). Of course I realize it will take me 2 workouts to your one to burn the same amount of fat, but that is okay with me. I just don't want to chance losing any muscle if I don't have to.
And yes-the wind sprints are wonderful-I only go for 15 seconds at a time-if I go a whole min.X20 you can come see me in ICU!And of course I agree with the weight training and the aspect of EPOC-even though these are considered anerobic excercise. When I was a kid 20 years ago and began weight training the medical profession totally disregarded weight training as effective excercise -even though that mentality is changing I still think the medical profession underates resistance training and wind sprints.

Hey SS,

Average glycogen storagen (not supercompensated) is about 18 g / kg. Loaded to 20g / kg an ave marathon runner might have 600g of muscle glycogen available. (LArge BB'er (loaded up) might have twice that.) 2-3 hr or continuous maximal running will lead to the "bonk" where glycogen levels in exercising muscle have reached cricitcal levels and you must slow down (fat cannot provide energy fast enough to maintain the exercise intensity). Rought estimates (would be higher in a highly trained persone) are that 6 alon can provide about 10 kcal of energy / min. Protine is more like 2 kcal / min.

As glycogen levels decline, fat use goe up (over the course of HOURS). GLycoven bottoms out and fat use, although maximal cannot pick up the pace. Protein use will increase, but is still FAR from being the major source of fuel (still < 10% of fuel mix).

Problem with long=-slow duration exercise is that is provides a signal for adaptatio nthat is diabolically opposed to that of wt. training. (See Kraemer et al., ~1998) The stress signals (among other thing) that a smjaller muscle fiber is appropriate - to reduce diffusion distances for fuel as it enters the cell from the blood. Long slow cardio interferes with msucel hypertrophy and certainly does not promote it, unless the trainee has been immobilized or extremely sedentary before training.

My point is this: No one exercises 4-5 hr (at least not sane people) to lose body fat. The use of muscle protein during exercise *as a fuel* is minimal. The stress of long distance, low(er) intensity endruance exercise does not promote or maintain muscle growth nearly als well as wt. training (if at all) and may interfere with muscle growth and speed its loss when dieting. (Yes, some guys put on size when dieting, although I think much of this is psycologically d/t the loss of body fat a/o d/t increased drug dosages.

A calorie is a calorie is a calorie. Lets compare:

LONG DURATION, LOW INTENSITY CARDIO:
-Expend 500 kcal during exercise
-No EPOC worth mentioning
-Poor stimulus for maintainig muscle size when dieting
-Mix of fuels to support exercise: 60% fat, 40% carbs

HIGH INTENSITY (OR INTERVAL) TRAINING:
-Expend 500 kcal during exercise
-EPOC may amount to 50 kcal
-Better stimulus to keep muslce size
-Mix of fuel: 90% carbs, 10% fat

Over the course of the day (in each case) if you expend *another* 2000 kcal and eat 2000 kcal, you will have about a 500 (or 550) kcal deficit. Fat loss witl be equal on a daily basis over the course of several days. These are the rules of thermodynamics - I didn't make 'em up. Naturally the dynamics of carb deposition (d/t different amaounts of use during exercise) will be different, but the caloric deficit must ultimately come from fat (or protein! - see below).

Over the course of months, if you lose more muscle with the low intensity cardio, your metabolic rate will decrease and so will the rate of fat loss: less muscle and more fat. (Note the study mentioned in the original article.)

THe above assumes that you are eating adequate protein in both cases.

I do NO cardio for show prep. I just lose leg muscle size if I do. I do it all with <EDIT> DIET (and willpower).

-Randy

It's great to have you both, LOL

bump

Real nice read guys

bump for anyone that missed this post

there is a lot of good info here

Cardio...bad...Cardio good...?

This past year I did cardio only for five minutes at the beginning of my workout as a warm-up. I know of several other competitive BBers who like myself, used to do a lot of cardio year round and during contest prep, but who also went to no cardio this past year.

Everyone I know who has gone to no cardio has come in just as lean and were able to hold more muscle mass pre-contest. I do think that there is merit to the theory that cardio can work against your goal of gaining lean mass. Certainly it can help you drop weight and fat. But overall it may also impede your ability to stay away from catabolism. (Especially for a natty BBer) I won't argue with Randy when he says <10% of your energy source will come from protein (i.e. muscle) but at least during a pre-contest diet it seems like it can be more than that if you over train or overdo cardio. Perhaps it is really the negative effect that the over training and too much cardio have on your CNS that inhibits LBM gain, but the end result can be the same.

I now clearly lean towards Randy's position that the best way to control bf is thorough the nutrition side of the house and not via cardio.

MD,

Haven't seen the data on a dieting BB'er, but I wouldn't be surprised if the % contribution of protein is higher (but not > 20%, I would imagine). Even so, if you burn 10 kcal / min and 2 of these are from protein, (1/2 gram), and go for an hour, this is 30 g of muscle protein (it smore complex than that, but this gets the basic idea across.) 30 g of muscle protein is about that contained in 120g of muscle (which is 3/4 water). Do this 5 days a week and that 600 g of muscle or more than 1 lb of muscle.

The biggest problem in my mind is really the stimulus of the cardio - it is damn near the polar opposite of that createed by wt. training.

Thanks for your input, man. Very cool to hear.

-Randy

Hey Randy and everybody
Glad to see all the input in this thread. I must admit I have been holding my trump card close to the vest and i figure that I better play it now since MD almost let the cat out of the bag.
I want to be clear that it is the study in RUNNERS that I am refuting.And my point in case is the loss of protein. Of course no bodybuilder or strenght athlete will train at 75%MHR for 3 or more hours. This is not excercise bros, this is TRAUMA-and there will be a huge release of cortisol which is our big nightmare as it practically melts muscle tissue away.I would be interested to know the cortisol status of a marathoner for an hour after such trauma and even for the next 2 or 3 days I bet it would be SKY HIGH. I am sure this is a major factor in the endurance athletes physique-probably hell on the libido too.So yes there may be a small loss of protein for caloric needs but i would think the residual effects on the hormonal axis would cause more protein loss over a few days than would the burning of protein for fuel and of course depressed testosterone levels to boot. Randy-I am confused about the table you described differentiating Long Duration Low Intensity vs. High Intensity
Your figure for fuel mix for the Low intensity group was 60%fat, 40% carb when the RUNNER study said this group would be 90%fat and 10% other.
Your figure for High Intensity fuel was 90%carb and 10% fat where the RUNNER study was 60% and 40%? Am i missing something here?
Also i would like to make a point concerning what I call the real world gym rat BB. You know-the guy that never competes, but trains his ass off, works 50 hours a week, doing the family scene(or if he is single doing the club scene). The guy that just can't pick and choose when he gets to the gym.I will call him X.
Let's say X hits the gym 4-5 times a week. Of course X hits the weights first(priorities man!) and trains till he is ready to puke. Now, going with conventional wisdom(which may not be so wise after all) he does some cardio after the wight training session for say 30 minutes, high intensity style. My point, or actually question, is since his glycogen levels are depleted(resistance training is considered anerobic, implying that the fuel source is glucose from glycogen) from lifting weights, what kind of effect will this have on the type of calories burned since he is glycogen depleted(at least partially depleted)? Seems to me as this would encourage a greater consumption of protein as fuel since not nearly as much carb would be on hand. Any ideas?What if X eats a low carb diet also?

Originally posted by supersport [/i]
Hey Randy and everybody
Of course no bodybuilder or strenght athlete will train at 75%MHR for 3 or more hours.
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Probably true (although I am sure there are exceptions). This would be a HR of 165 or so.
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This is not excercise bros, this is TRAUMA-and there will be a huge release of cortisol which is our big nightmare as it practically melts muscle tissue away.I would be interested to know the cortisol status of a marathoner for an hour after such trauma
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Cortisol will increase progressively over the course of the exercise bout. HIgher in heat, higher w/ higher intensity.
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and even for the next 2 or 3 days I bet it would be SKY HIGH. I am sure this is a major factor in the endurance athletes physique-probably hell on the libido too.So yes there may be a small loss of protein for caloric needs but i would think the residual effects on the hormonal axis would cause more protein loss over a few days than would the burning of protein for fuel and of course depressed testosterone levels to boot.
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Cortisol levels will depend upon what the athelte is used to. Athletes of high caliber who train like this without overtraining will have cortisol under control. These althletes also are in nitrogen balance.
Of course, if this were a marathon, this is highly catabolic for most athletes.
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Randy-I am confused about the table you described differentiating Long Duration Low Intensity vs. High Intensity
Your figure for fuel mix for the Low intensity group was 60%fat, 40% carb when the RUNNER study said this group would be 90%fat and 10% other.
Your figure for High Intensity fuel was 90%carb and 10% fat where the RUNNER study was 60% and 40%? Am i missing something here?
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% kcal from carbs increases with intensity. The values cited in the article consider only the kcal burned ABOVE AND BEYOND what would have been consumed at rest. (I know the researchers who did the work.)
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Let's say X hits the gym 4-5 times a week. Of course X hits the weights first(priorities man!) and trains till he is ready to puke. Now, going with conventional wisdom(which may not be so wise after all) he does some cardio after the wight training session for say 30 minutes, high intensity style. My point, or actually question, is since his glycogen levels are depleted(resistance training is considered anerobic, implying that the fuel source is glucose from glycogen) from lifting weights, what kind of effect will this have on the type of calories burned since he is glycogen depleted(at least partially depleted)? Seems to me as this would encourage a greater consumption of protein as fuel since not nearly as much carb would be on hand. Any ideas?What if X eats a low carb diet also?
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He will oxidize more fat, but not more kcal (small caveat here), when glycogen levels are lower. Same goes for being on a low carb diet. THe previous exercise will elevate epinephrine and lower insulin, too, which will help mobilize fat.

-Randy

Randy
I have a question for you. I have been BB'd since 1982-never competed but have made good gains over the years. I did the high carb thing in the eigties when that was "in" and low carb now. My question is this-I have always noticed that whether I do low intensity or high intensity cardio that the next day my muscles are always "flat". I have tried everything from no carbs after cardio to loading with creatine and simple sugars etc. Caloric intake has always been sky high-1.5-2 lbs red meat per day,half gallon of ice cream per day, meal replacements,protein powders etc. last few years i have given up ice cream (I am a recovering ice cream junkie!) and eat cleaner, but still experience this muscle flatness after cardio. Any ideas? You and MD posted that you only use diet and no cardio for show prep-do you use any thermogenic agents (t-3, clen, ECA stack, etc) or just modify your diet?