Fat Burning Zone...

Nicole

Female Moderator, Fitness Professional
Why the "Fat Burning Zone" Is a Myth
by Jonny Bowden, M.A., C.N.S.

I want you to do me a favor. I know you're gonna hate it, but please do it anyway. I promise you it'll make life so much simpler, make things so much clearer, and save us so much time in the coming months.

I want you to go back to school with me for a minute, and review some math.

Now, when I teach this stuff to trainers, as soon as they hear "math" their eyes glaze over and they look like a collective herd of deer caught in the headlights of a Mack truck. But, honestly, how are you going to talk sensibly about calories, diets like "40/30/30," percentages of calories from protein, decoding a food label, or anything else along those lines without unfuzzy-ing up some of the basics in the math department?

Which brings me to the area of "fat burning" zones.

See, one of the biggest misunderstandings and "myth-conceptions" in the field of exercise and weight loss has been around the field of fat burning. Aerobic teachers are constantly admonishing their students to work at a slower rate so they can "burn more fat." Almost all cardio equipment in the gym has a "fat burning" program, and we fitness professionals are constantly bombarded with questions from clients about how to get their heart rate in the target "fat burning zone."

The misconceptions come from a basic confusion between percentages and absolute amounts. See, at rest, the body is always burning a mix of fuels. All other things being equal, it doesn't like to burn protein, so that leaves fats and carbohydrates (more technically, fatty acids and glucose). At rest, the "average" person burns about 70 percent fat and 30 percent carbs. As one moves from rest to activity, the percentage of fuel coming from fat decreases and the percentage coming from carbs increases. The more intense the exercise, the more carbs and the less fat in the mix, until you reach the point called the "anaerobic threshold" where you're going at about your intensity limit. At that point, 99 percent or more of your fuel is pure carbohydrate and 1 percent or less is coming from fat.

Now, this situation has led many people to assume that in order to "burn fat" they need to exercise at lower intensities. They're missing the boat. Why? Because while at rest, although a higher percentage of your calories is indeed coming from fat, you are ultimately burning a lower absolute number of calories. At higher intensity exercise, the percentage of calories from fat goes down, true -- but it is a percentage of a significantly higher number.

To illustrate this critical difference, I often ask audiences to picture Ross Perot standing next to me. Then I ask them, "Would you rather have 90 percent of all the money I have in the world, or 3 percent of all the money Mr. Perot over here has?" When they give the obvious answer, I say, "But why? 90 percent is so much higher than 3 percent!"

They get the picture.

So, let's say you're exercising at a fairly low intensity that burns, oh, 100 calories in a half-hour. Let's say that 70 percent of those calories come from fat. Your neighbor, however, is working out much harder, outside the magical "fat burning" zone: She's burning up, say 300 calories in that same half hour, but only 50 percent of those calories are from fat. Now do the math. You're burning a higher percentage of fat, but 70 percent of your 100 calories equals 70 fat calories burned. Your neighbor, on the other hand, is burning a lower percentage of fat, but she has burned up 50 percent of 300 calories, or 150 fat calories, more than twice what you've burned in the same period of time!

Get it?

I hope this whets your appetite, cause it's going to get even more interesting as we progress over the next year. Stay tuned!
 
Last edited by a moderator:
Yeah, if the 150 calscome from fat then the other 150 most likely will come from muscle. I'm guessing both these scenarios are done w/little muscle glycogen for fuel, like in the morning before you eat. Definately the lower intensity is more muscle sparring, you just have to go longer at it.
 
Gimp said:
yeah, I'd like to know as well. I was always of the opinion that slow but steady cardio sessions are muscle sparing and burn fat. I usually do 40 mins. on the treadmill at an incline of 12-15% at a speed of 3. I lean down quickly with this method and seemingly keep lean mass.

I do the same and it seems to work really well. I get better results from the steep incline on the treadmill than I do with the Precor Elliptical Cross Trainer.
 
Nicole said:
Why the "Fat Burning Zone" Is a Myth
by Jonny Bowden, M.A., C.N.S.

I want you to do me a favor. I know you're gonna hate it, but please do it anyway. I promise you it'll make life so much simpler, make things so much clearer, and save us so much time in the coming months.

I want you to go back to school with me for a minute, and review some math.

Now, when I teach this stuff to trainers, as soon as they hear "math" their eyes glaze over and they look like a collective herd of deer caught in the headlights of a Mack truck. But, honestly, how are you going to talk sensibly about calories, diets like "40/30/30," percentages of calories from protein, decoding a food label, or anything else along those lines without unfuzzy-ing up some of the basics in the math department?

Which brings me to the area of "fat burning" zones.

See, one of the biggest misunderstandings and "myth-conceptions" in the field of exercise and weight loss has been around the field of fat burning. Aerobic teachers are constantly admonishing their students to work at a slower rate so they can "burn more fat." Almost all cardio equipment in the gym has a "fat burning" program, and we fitness professionals are constantly bombarded with questions from clients about how to get their heart rate in the target "fat burning zone."

The misconceptions come from a basic confusion between percentages and absolute amounts. See, at rest, the body is always burning a mix of fuels. All other things being equal, it doesn't like to burn protein, so that leaves fats and carbohydrates (more technically, fatty acids and glucose). At rest, the "average" person burns about 70 percent fat and 30 percent carbs. As one moves from rest to activity, the percentage of fuel coming from fat decreases and the percentage coming from carbs increases. The more intense the exercise, the more carbs and the less fat in the mix, until you reach the point called the "anaerobic threshold" where you're going at about your intensity limit. At that point, 99 percent or more of your fuel is pure carbohydrate and 1 percent or less is coming from fat.

Now, this situation has led many people to assume that in order to "burn fat" they need to exercise at lower intensities. They're missing the boat. Why? Because while at rest, although a higher percentage of your calories is indeed coming from fat, you are ultimately burning a lower absolute number of calories. At higher intensity exercise, the percentage of calories from fat goes down, true -- but it is a percentage of a significantly higher number.

To illustrate this critical difference, I often ask audiences to picture Ross Perot standing next to me. Then I ask them, "Would you rather have 90 percent of all the money I have in the world, or 3 percent of all the money Mr. Perot over here has?" When they give the obvious answer, I say, "But why? 90 percent is so much higher than 3 percent!"

They get the picture.

So, let's say you're exercising at a fairly low intensity that burns, oh, 100 calories in a half-hour. Let's say that 70 percent of those calories come from fat. Your neighbor, however, is working out much harder, outside the magical "fat burning" zone: She's burning up, say 300 calories in that same half hour, but only 50 percent of those calories are from fat. Now do the math. You're burning a higher percentage of fat, but 70 percent of your 100 calories equals 70 fat calories burned. Your neighbor, on the other hand, is burning a lower percentage of fat, but she has burned up 50 percent of 300 calories, or 150 fat calories, more than twice what you've burned in the same period of time!

Get it?

I hope this whets your appetite, cause it's going to get even more interesting as we progress over the next year. Stay tuned! [/B]

When I used to train at Venice, CA Gold's, we did this Intrafit Program that they have and they had the same theories on the "lower intensity" cardio. They made us purchase the heart rate monitors and the whole shebang and we soon lost our patience and went back to our own way of doing cardio and had far better results. The latter was way to slow for our liking...

Still have the heart rate monitor, but never use it:D
 
Last edited by a moderator:
fable said:
what happens if you are on a low carb diet, with high intensity?

This is the one situation where I disagree with the article. If i'm on a low-carb diet, I'd rather do low intensity cardio to burn mostly fat, and save the few carbs I have for my weight sessions which absolutely carbs for high intensity.
 
I think there is def a happy medium there for burning the most cals while sparing our recovery energy. With out the use of gear over training becomes a major concern with me. If i hit the iron hard i can't expect to kick ass with intense cardio. Something has to give, and it will be your gains, and general energy levels. For me i feel that the 60 to 75 % of my mhr is just about perfect. Just have some patience. With proper DIET and training.
 
i'd have to stick with the low intensity long duration route
this is something that has always worked for me
 
Like DIAL TONE, I prefer low-impact cardio to burn fat. I'd rather brisk walk around my neighborhood for an hour, than go on a boring treadmill for 30 minutes at the gym.
 
Even though the maths works in the first argument that more calories at lower % fat burn is better for fat burn overall, the maths depends very significantly on the % used.

e.g. you burn 50% of 200 calories of fat at low intensity
= 100 fat calories

or you burn 15% of 500 calories of fat at high intensity
=75 fat calories

in this example, high intensity maybe burning more cals, but its burning LESS fat.

This is obv significant on low carb diets and muscle sparing low intensity cardio is probably better.

It even seems futile when applied to high carb diets e.g. you have to take in necessary carbs before/during the high intensity cardio to spare your muscle i.e. provide enough glycogen else you will deplete and burn muscle. This intake offsets any benefit from the higher cals burnt and you're burning less fat!!!

Answers on a postcard please Nicole.
 
i think what hes getting at is if you dont burn those carbs off they are going to become stored fat anyway... (key phrase i think!)
 
There is practical interest in identifying the exercise intensity that oxidizes (ie, burns) the most body fat. As indicated in Figure 3, during exercise at 25% of O2max, a high percentage (60***8211;85% of O2max) of energy is derived from fat, whereas during exercise at 65% of O2max, 50% of the energy is derived from fat. However, because the total energy expenditure is 2- to 3-fold higher at 65% of O2max than at 25% of O2max, the actual absolute rate of fat oxidation (MJ***8226;kg-1***8226;h-1 or kcal***8226;kg-1***8226;min-1) is much higher at the higher intensity, largely owing to oxidation of IMTG. In terms of using exercise that can be performed for only a limited amount of time (eg, 1 h/d) to lower body fat stores, it seems that exercise at 65% of O2max would be more effective than exercising at 25% of O2max, because absolute fat loss from the body would be higher.

Prolonged exercise
Shown in Figure 4 are the alterations in substrate mix that occurred throughout several hours of exercise at 65***8211;75% of O2max in endurance-trained men after an overnight fast (6, 19, 53). The relative contribution of fat and carbohydrate changes only slightly: fat oxidation increases and carbohydrate oxidation declines slightly. The most dramatic shift in substrate oxidation occurs in the source of carbohydrate energy. With increasing duration of exercise, the contribution of muscle glycogen declines as its stores are lowered, and the contribution of blood glucose increases to remarkably high amounts. This shift from muscle glycogen to blood glucose is necessary to maintain the total carbohydrate oxidation that is required of exercise at this intensity because of the limitations in fat oxidation. This progressive and heavy reliance on blood glucose oxidation forms the basis for carbohydrate ingestion during prolonged exercise (53). After 1***8211;2 h of exercise at these intensities, blood glucose concentration begins to decline because of an imbalance, whereby glucose disappearance from blood becomes greater than glucose appearance into blood (36, 53). Reductions in liver glycogen stores contribute to the inability to maintain blood glucose concentration. As a result, people exercising in the fasted state usually become hypoglycemic (ie, blood glucose <3 mmol) during the third hour and then become fatigued (25, 53). Fatigue is preceded by a decline in carbohydrate oxidation and is related to the depletion of muscle glycogen with concomitant hypoglycemia. The metabolic stress of substrate depletion in the exercising muscles at the point of fatigue suggests an energy production imbalance (eg, ATP flux), as reflected by increased ammonia concentrations (28). Carbohydrate ingestion throughout exercise maintains blood glucose concentration and carbohydrate oxidation, which delays fatigue (54).
 
Last edited by a moderator:
i shouldn't think anyone on a ketogenic diet would want to use insulin. that would throw them out of ketogenesis, just like eating carbs would.
 
nickk23 said:
i shouldn't think anyone on a ketogenic diet would want to use insulin. that would throw them out of ketogenesis, just like eating carbs would.


I thought you could use Insulin to get back into ketosis faster...
 
yeah i think insulin regulates your blood sugar, it isnt sugar, so it wouldnt throw off your ketosis. and i have also heard it helps get into ketosis state
 
Well, the insulin would lower the blood sugar, but i thought ketosis arose from depleted glycogen stores rather than low blood sugar. Im a diabetic, and when i go hypo (low blood sugar) i doubt i immediately enter ketogenesis because my glycogen stores are still well stocked.

Also, if you take insulin, you HAVE to have sugar with it which will then throw you out of ketosis in my opinion.
 
yeah i had a couple friends who were diabetic and they would drink caprisun or mountain dew if they didnt have their dose on them
 
Back
Top