Fastest way to loose weight?

[decypheredbeats]

Originally posted by Sean Dempsey


no.

For the fast results, do this:

go down to a track, or anywhere, but tracks are best.

SPRINT as hard as you can for 9 seconds. Walk for 27 seconds. Repeat this for 45 minutes without stopping.

If you do that for 6-8 weeks, you will lose fat, and lots of it.

HIIT - High Intensity Interval Training, it's one of the most effective ways to lose fat, and also really condition yourself.

most people won't do it.

thank you, when are people gonna learn this is the best form of excercise to lose wieght?

[Sean Dempsey]

HIIT training (I know it's saying training twice in a row... like ATM machine..).

HIIT Training is effective because of how it uses myoglobin stores in the muscle fibers to extract the energy. the HIIT method makes you burn MORE fat over a 24-36 hour period than you would if you jogged for 90 minutes.

Basically, HIIT Training makes you burn more fat over the course of the day once you start training this way, and has alot to do with MYOGLOBIN.

do a google search for "HIIT" and "Myoglobin" and you'll find alot.

This will shred any person down to ligaments and sinew.

I don't feel like typing, I have to go roll in 10 minutes, but I'll post this article

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HIGH-INTENSITY INTERVAL TRAINING:

THE OPTIMAL PROTOCOL FOR FAT LOSS?

James Krieger

As exercise intensity increases, the proportion of fat utilized as an energy substrate decreases, while the proportion of carbohydrates utilized increases (5). The rate of fatty acid mobilization from adipose tissue also declines with increasing exercise intensity (5). This had led to the common recommendation that low- to moderate-intensity, long duration endurance exercise is the most beneficial for fat loss (15). However, this belief does not take into consideration what happens during the post-exercise recovery period; total daily energy expenditure is more important for fat loss than the predominant fuel utilized during exercise (5). This is supported by research showing no significant difference in body fat loss between high-intensity and low-intensity submaximal, continuous exercise when total energy expenditure per exercise session is equated (2,7,9). Research by Hickson et al (11) further supports the notion that the predominant fuel substrate used during exercise does not play a role in fat loss; rats engaged in a high-intensity sprint training protocol achieved significant reductions in body fat, despite the fact that sprint training relies almost completely on carbohydrates as a fuel source.

Some research suggests that high-intensity exercise is more beneficial for fat loss than low- and moderate-intensity exercise (3,18,23,24). Pacheco-Sanchez et al (18) found a more pronounced fat loss in rats that exercised at a high intensity as compared to rats that exercised at a low intensity, despite both groups performing an equivalent amount of work. Bryner et al (3) found a significant loss in body fat in a group that exercised at a high intensity of 80-90% of maximum heart rate, while no significant change in body fat was found in the lower intensity group which exercised at 60-70% of maximum heart rate; no significant difference in total work existed between groups. An epidemiological study (24) found that individuals who regularly engaged in high-intensity exercise had lower skinfold thicknesses and waist-to-hip ratios (WHRs) than individuals who participated in exercise of lower intensities. After a covariance analysis was performed to remove the effect of total energy expenditure on skinfolds and WHRs, a significant difference remained between people who performed high-intensity exercise and people who performed lower-intensity exercise.

Tremblay et al (23) performed the most notable study which demonstrates that high-intensity exercise, specifically intermittent, supramaximal exercise, is the most optimal for fat loss. Subjects engaged in either an endurance training (ET) program for 20 weeks or a high-intensity intermittent-training (HIIT) program for 15 weeks. The mean estimated energy cost of the ET protocol was 120.4 MJ, while the mean estimated energy cost of the HIIT protocol was 57.9 MJ. The decrease in six subcutaneous skinfolds tended to be greater in the HIIT group than the ET group, despite the dramatically lower energy cost of training. When expressed on a per MJ basis, the HIIT group's reduction in skinfolds was nine times greater than the ET group.

A number of explanations exist for the greater amounts of fat loss achieved by HIIT. First, a large body of evidence shows that high-intensity protocols, notably intermittent protocols, result in significantly greater post-exercise energy expenditure and fat utilization than low- or moderate-intensity protocols (1,4,8,14,19,21,25). Other research has found significantly elevated blood free-fatty-acid (FFA) concentrations or increased utilization of fat during recovery from resistance training (which is a form of HIIT) (16,17). Rasmussen et al (20) found higher exercise intensity resulted in greater acetyl-CoA carboxylase (ACC) inactivation, which would result in greater FFA oxidation after exercise since ACC is an inhibitor of FFA oxidation. Tremblay et al (23) found HIIT to significantly increase muscle 3-hydroxyacyl coenzyme A dehydrogenase activity (a marker of the activity of b oxidation) over ET. Finally, a number of studies have found high-intensity exercise to suppress appetite more than lower intensities (6,12,13,22) and reduce saturated fat intake (3).

Overall, the evidence suggests that HIIT is the most efficient method for achieving fat loss. However, HIIT carries a greater risk of injury and is physically and psychologically demanding (10), making low- and moderate-intensity, continuous exercise the best choice for individuals that are unmotivated or contraindicated for high-intensity exercise.

[Szczepankiewicz]

That is absolutely ungay.

Thanks Sean!

[sk12879]

Originally posted by Serrada
The healthy way to do it is to find your current calorie intake and subtract 50 to 200 calories a week depending on your current weight. Reduce your serving sizes!

I believe what he meant to say here is to reduce your daily caloric intake by 250. Also, increase your exercise to burn an additional 250 calories per day. That's 500 per day (for you non-mathematicians) - over 7 days....3500. Ironically, a 3500 calorie deficit will result in 1 lb of safe weight loss per week. 1 to 2 lbs is considered safe loss.

More fish, nuts, seeds, vegetables. Fewer carbs...especially processed carbs (i.e. white sugar, etc). Cut desserts, sweets, juices that aren't 100% (and even limit those). I usually try to cut off on most all carbs at around 4pm. I eat a big breakfast to get my metabolism revved up (also, something as simple as 100 pushups can get your body burning fuel in the morning) and give my body fuel to burn. More meals, make them smaller....eat 5 or 6 times a day. I have a big breakfast (probably 75% of my carbs for the day), snack of walnuts (Omega 3's, protein) or an apple or pineapple, small lunch, snack of canned salmon, yogurt, and/or walnuts/almonds, small dinner.

Good post Sean! I love HIIT and it seems that many people are unaware of its benefits. It takes less time than jogging and has far better results. Think about it....not too many sprinters that aren't shredded (yearning for my days as a high school sprinter again).

[Serrada]

1) c0bra use Sean Dempsey explosive routine if you want to become lets say a LINEBACKER and remain the size of a LINEBACKER!

Otherwise use what cardiologist use. 70% to 80% of your maximum heart rate for your age for a cardiovascular workout (jog to a run speed); 60% to 70% of your maximum heart rate for your age for a fat burn work out (Walk, Speed walk, jog). You did say you what to lose weight right?

Start with at least 15min. and work your way up to a min. of 28 min. 3 to 4 times a week.

What Sean Dempsey is similar to what is use to gain cardio. There called 5 to 1’s. You start by walking for 5 min. then run for 1 min. You do this for 15 min. so you run twice. Also, 3 to 4 times a week. Then, week two you do 4 to 1’s and so on until your running for 15 min. straight. Then you do 16 min. and so on.

To burn fat FAST maintain 60% to 70% of your maximum heart rate.

Of course all of this is adjusted to the level of activity you currently are at.

2) sk12879 is on the right track, but if your not doing any of this I can guarantee you will lose at least 3 to 5+ pounds each week.

To further enlighten you on the diet, not the following:

1) rank yourself on a level of 14 through 20 as far as your activity level. 20 being the most active. Multiply that number by your weight. That is your daily calorie intake. To lose fat subtract the 50 to 200 calories per week from your basic diet. If you’re a 170lb. person and you want to lose fat fast and increase muscle (which exponentially will help you burn fat). Let say your fairly active this is a martial arts forum after all. 18-active * 170 = 3060 calories per day. 3060 – 100 = 2960. So week 1 you consume 2960 calories per day week 2 you consume 2,860 per day. Etc.

In three months when you weight 40lbs less and can thank me. Of course continue until you reach your 60lb goal. Then, you can eat what you what as long as you maintain the calorie intake.

I have trained hundreds of people and it works every time. But you must include all three factors: 1) calorie intake reduction for weight loss 2) weight training 3) fat burn cardio

[decypheredbeats]

HIIT is the best for fat loss

heres some support


Benefits Of HIIT

A study at Laval University in Quebec, Canada found that HIIT cardio helped trainees loose nine times more fat than those who trained the traditional way (moderate speed for 20-60 minutes). Combine HIIT with your weight program and you boost your metabolism through the roof!

The reason that HIIT is so successful is this:

When you work at a high intensity, you burn more total calories per pound of body weight.
High Intensity workouts such as weight training and HIIT boost growth hormone levels.
Elevates the body’s metabolism throughout the ENTIRE DAY!
What does this mean for you? The more calories that you burn in a day, the more weight you are able to lose. Even if weight loss is not your goal, HIIT is for you. Athletes will see better gains from doing HIIT cardio as opposed to traditional cardio. Unless you are training for a marathon, you do not keep a constant pace during your sport. All sports whether it be soccer or football, even baseball or basketball have a point where you need to change gears and hit a full sprint.

HIIT will not only help your cardiovascular system, but will train the Anaerobic, ATP/CP system as well. Not only will you increase your cardiovascular endurance but improve your raw speed and explosiveness as well!

Conclusion

I will let the studies speak for themselves. HIIT provides a more effective workout in much less time! Everyone can benefit from HIIT cardio whether it be the person who is trying to lose weight or the professional football player training for the upcoming NFL season! Give HIIT a try and I am sure that you will not go back to the traditional way of performing cardio again!

References:
1. Horn, Beth. "Shock Therapy" FLEX Magazine July, 2003. Page 110

[decypheredbeats]

want more?

mgkurilla@comcast.net

Note: This is part one, click here for part two!
click here for part three!

Most bodybuilders incorporate some form of aerobic conditioning or "cardio" into their workout routines in order to develop and maintain cardiovascular fitness for both health reasons as well as increasing endurance capacity. In addition, cardio along with dieting or caloric restriction have been the cornerstones for bodyfat management. Unfortunately, there has been much misinformation and misapplication regarding the actual impact of aerobic exercise with regards to bodyfat management.

For the most part, this derives from the fact that scientific studies upon which these ideas are based are usually part of weight loss / fitness programs for either obese individuals or those with cardiac disease.2,16,17,28 In addition, public health advocates in an effort to induce the greatest number of couch potatoes to take up exercise have typically reduced scientific information to a simplified, palatable form that is directed towards overweight, sedentary individuals with little applicability or guidance for someone who is already fit.

This three part article will review the basics of exercise physiology in order to understand the role of fuel selection (fat versus carb burning) within the context of an overall aerobic conditioning program. Next, in part two, the role of the post exercise period will be detailed.

Interval training in terms of its impact on cardio programs and bodyfat management will also be introduced. Finally, in part three, various interval routines will be presented with results from studies in order to compare the various methodologies. In addition, simplified interval routines with proven results will be outlined. In as little as 4 weeks, substantial progress in terms of aerobic fitness as well as bodyfat reduction can be achieved with the right program along with the right commitment.

Exercise Physiology - How To Burn Fat For Energy Instead Of Carbs Or Protein

In order to understand the physiology of interval training and its applications, a general outline of exercise physiology must be introduced. Energy for exercise (or any physical activity) is derived from two primary, dietary fuel sources: carbohydrates and fats. Protein can also be used, but generally, durations of less than 60 minutes involve little protein burning, although under extreme low carb conditions, this can increase.3 For each fuel, there are also two primary sources working muscle can call on: intramuscular (within the muscle itself) or peripheral (derived from the blood).

When peripheral sources are utilized, glucose (the major carb or sugar form in the body) comes either from the blood itself or the liver which releases glucose it has either stored or produced in order to maintain blood sugar levels and prevent hypoglycemia.

Peripheral fat stores are any fat depots in the body including subcutaneous (directly under the skin) and intra-abdominal (fat stored underneath the abdominal muscles) fat. The process of releasing fat from peripheral fat stores into the blood is known as lipolysis. Intramuscular stores of carbs are known as glycogen (a large complex of glucose attached to itself). Intramuscular stores of fat are in the form of triglyceride, similar to the storage form of fat in peripheral fat stores.

[Nit]

ULTIMATE WAY TO POWER WIEGHT LOSS:

1. Eat lots of laxative

2. Place Sellotape across the mouth

3. Wait

4. Lose lots of wieght INSTANTLY

5. Wait

6. LOSE more Wieght through the stright regimine

7. wait

8. die

[decypheredbeats]

part 2
How A Muscle Determines It's Fuel

During exercise four fuel sources (two carb and two fat) are typically utilized. How a muscle determines its fuel mixture, both the form of the fuel and its source, is based on:


The intensity and duration of the exercise.
The training status of those specific exercising muscles
The general diet (relating to specific percentages of fats and carbs).
The time interval since the last meal prior to exercise.
In addition to the exercise itself there is also a recovery period after exercise where energy expenditure is greater than an equivalent period of time following rest. Finally, the exercise itself induces hormonal changes that impact longer term fuel selection and utilization as well as fuel (that is food) intake.


By following an exercise routine, you will burn more fat and calories even while you are at rest!
There has been a lot of confusion about intensity and duration with regards to fuel selection in terms of optimal training protocols specifically related to bodyfat reduction. A better understanding of the overall process will clear the air so stick with me! While carbs and fats supply the major energy fuels for most activities, they have dramatically different properties in our bodies. One major difference is that fats require more oxygen to burn than carbs. This implies that as exercise intensity is increased, there is a natural shift to burning more carbs because less oxygen is needed to extract the needed level of energy output to support that intensity. When oxygen is not limiting (that is at low intensity), fats are the preferred fuel. Now, the situation is not as simple a low intensity burns fat / high intensity burns carbs.

Carbs are utilized to some extent at all intensity levels with a gradual and progressive absolute as well as percentage increase as intensity is increased. Fats on the other hand, provide the bulk at low intensity and gradually increase with intensity (in this case, absolute amount of fat burning increases, even while the percentage contribution to the total is going down), but then taper off at moderate to high intensity because of oxygen limitations (during this phase, the absolute as well as percentage declines). However, the details of fuel selection get more complicated because of differences in where these fuels come from. The source of these fuels also has implications especially in the post-exercise period which in turn plays a role in bodyfat management.

Understanding The VO2max

To understand fuel selection in more detail, the concept of VO2max will be introduced. VO2max simply refers to the maximum rate of oxygen you can utilize during exercise. As intensity increases so does your heart rate and so does oxygen utilization. Eventually, at some point if you increase intensity further, your heart rate will not increase further (you've reached your max heart rate) and oxygen utilization won't go up anymore; your oxygen usage has maxed out (overall intensity can still increase, but you are going anaerobic at that point). Intensity then can be indicated by some percentage of that maximum aerobic intensity. Therefore, we can quantify intensity with some percentage of VO2max.

At rest, you are about 5-8% of your VO2max. Resting VO2 is sometimes referred to as a MET or metabolic equivalent. Some exercise equipment can relate the workload as the number of METs. Low intensity is typically in the range of 25 - 40% VO2max. A 25% VO2max effort would be a comfortable walking pace. 40% would be in the range listed as the fat burning zone on some cardio equipment. 45 - 70% VO2max is squarely in the range of moderate intensity and is labeled as the aerobic training zone.


Bonus! To calculate how many calories you are burning during over 600 exercises and activities, click here to use our online calculator! This is based on the MET calculations.
A trained individual should be able to maintain this level of intensity for 1.5 - 3 hours or more. Above 70-75% VO2max is in the range of high intensity. Duration is severely limited because at these levels, the reliance on carb burning to generate a high percentage of the total energy begins to produce lactic acid. At some point (that is, a specific percentage of your VO2max), the level of lactic acid hits a threshold and begins to skyrocket in the blood and brings about muscle failure.3,26 Once you are above your lactic acid threshold, duration can only be sustained for 3-10 minutes.3

Now that intensity levels are set, we can follow fuel selection across the intensity spectrum, since both fuel usage and source is determined by intensity.21,22 At low intensities, fat is primarily used (assuming no pre-exercise meal as been ingested). In addition, the source of the fat is circulating fat in the blood derived from release of peripheral fat stores. In other words, at low intensity, such as casual walking, calories are derived from fat coming from peripheral fat stores and supply the major fraction (85%) of total calories expended. The remainder of the calories is supplied by carb burning from uptake of sugar in the blood. However, at this level of intensity the overall level of caloric expenditure is low.

A resting value of caloric expenditure is on the order about 1 calorie per minute which scales roughly with lean body mass. The more muscle you have, the more calories you will burn at rest. Low intensity exercise like casual walking ups this value to the range of 3 - 6 calories per minute. This is the basis for recommendations for low, sustained intensity levels for fat burning, sometimes called the fat burning zone, since about 85% of the energy expended will be derived from fat burning. However, total calories burned and hence the quantity of fat actually burned will be quite low. In addition, these intensities are too low for a substantial aerobic training effect to occur which has long term impact on fuel utilization, during and after exercise.23

As an example, even at the upper range of 6 calories per minute, one hour at this intensity yields 360 calories expended. Since only 85% of these calories are fat derived, we've burned 306 fat calories or 34 grams of fat (1 gram of fat is worth 9 calories). In terms of weight control, that's not too bad since 34 grams of fat can be a substantial portion of one's daily intake, but from the standpoint of fat reduction, over 11 hours of this exercise would be necessary to burn off one pound of fat (about 3500 calories per pound).

The general rule of 20 - 30 minutes for these types of activity to "turn on fat burning" comes from the idea that as fat is pulled out of the blood by the working muscles, the level in the blood will eventually begin to drop after, surprise, 20 - 30 minutes. As this happens, there is a hormonal response to restock fat levels in the blood. These hormones (both adrenaline and noradrenaline, coming from adrenal glands and nerves, respectively) stimulate fat cells to break down their fat stores and release them into the bloodstream, through the process of lipolysis.7 This is also where diet and food composition is important, since insulin released in response to dietary intake of carbohydrate opposes the action of these hormones. Insulin is antilipolytic, shuts down fat release, and promotes fat storage in peripheral fat cells.

Increasing Exercise Intensity: More Or Less Fat Being Burned?

As the intensity of the exercise is increased, the whole process ramps up for greater energy expenditure. Both fat and carb burning are increased. Although carbs assume an increasing percentage of the total, the absolute level of fat burning still continues to increase. The major difference with moderate versus low intensity is for the source of the fat derived energy. As intensity is increased, the working muscles require more oxygen and hence more blood flow, which explains the increase in heart rate (more blood volume and hence more oxygen is pumped per minute). In addition, since muscle is only about 25% efficient in terms of work, 75% of the calories expended are lost as heat. This heat must be dissipated which is why we sweat. In order to sweat, some blood flow must be directed to the surface skin, which is different from the peripheral fat stores just below the skin.

These two factors (more blood to the working muscle and increased blood flow to the skin for sweating) combine to limit the blood flow that can be allocated to peripheral fat stores for loading the blood with released fat through.23 Thus, at some point with increasing intensity, the release of fat into the blood stream from peripheral fat stores levels off.4,21,23 Peripheral fat stores have a maximum rate of fat release into the blood which has been determined to be the primary limitation for this fuel source.7,23 However, the rate of fat burning by the working muscle continues to increase.

To meet increased energy needs for moderate intensity (relative to low intensity), the muscle begins to breakdown its own fat stores, the intramuscular triglyceride. Since this store is more limited than the peripheral fat store, the muscle prefers to preserve this store until absolutely needed. In other words, at low intensities, working muscles prefer to utilize fats from peripheral fat stores which are the most flexible in terms of fat storage (because they can become huge). But peripheral fat stores are limited in the rate at which they can release fat and so fat stores within the working muscle itself are involved when the intensity increases enough to require more fuel than peripheral fat stores can provide. Intramuscular fat stores are limited by the absolute amount of fat available.

Your Maximum Fat Burning Zone

Maximum fat burning rate occurs during moderate intensity at about 60 - 65% VO2max which corresponds to about 75% max heart rate for most people (this assumes an aerobically trained individual).1 The absolute burn rate is size dependent, but will typically fall into the range of about 0.5 - 0.8 grams of fat per minute with about equal contributions from peripheral and intramuscular sources. Total caloric expenditure for moderate intensity exercise again is size dependent (larger people expend more calories because they are moving larger masses and working larger muscles) and falls in the range of about 8 - 15 calories per minutes with fat contributing on the order of about 50 - 70% of the total caloric expenditure. With longer durations, this amount tends to the higher value, mainly due to intramuscular glycogen depletion that occurs at this level of intensity. Most trained individuals can sustain this rate of expenditure for 1.5 - 3 hours, at least, but because of the level of carb burning at this intensity, the duration will be limited by total carb stores in the body.

As intensity is further increased (to 85% VO2max), oxygen supply begins to become limiting. This causes a further shift to greater carb burning with breakdown of the muscle's intramuscular store of carb in the form of glycogen1.21,22,23 Similar to fat burning, as intensity is increased, fuel source shifts to a greater reliance on intramuscular carb stores in the form of glycogen. If the level of intensity is held below the lactic acid threshold (which varies from the high 60's% of VO2max to the 80's%), the activity can be sustained for about 45 - 60 minutes until glycogen stores are exhausted necessitating a fall back to an intensity level where fat can supply the majority of energy needs.

If on the other hand, the intensity is above the lactic acid threshold, then in a matter of a few minutes, lactic acid levels will climb intolerably high in the blood and failure results.3 As will be seen in part II, interval training is designed to improve this situation.

An important aspect to this complex pattern of fuel usage is the effect of training on fuel selection. This is vital to understand because an understanding of training effects identifies the orientation of the overall system and permits exploitation of fuel selection for maximum desired results. Simply put, aerobic training serves to enhance greater energy generation from fat sources at all intensity levels.3,12,14 The rationale for this is simple, carbohydrate stores of energy are quite limiting and can be depleted during the course of a single exercise session of sufficient intensity and/or duration.

During a marathon race, 'hitting the wall' occurs when carb stores have been depleted and underscores the focus on carb loading regimes. Under conditions of glycogen depletion, the muscle must begin to breakdown protein since branched chain amino acids present in protein can substitute for carbs, in terms of supplying energy directly as well as substituting for carbs in the process of maintaining the system for aerobic energy generation (something fats cannot support). Alanine (another amino acid in protein) released from protein breakdown can also be converted by the liver into glucose further increasing carb supplies from the blood.

Training allows for a higher sustainable level of intensity to be performed by sparing carbs in working muscle (by reducing the rate of depletion) and generating a greater percentage of energy from fat derived sources. In other words, since at a given intensity level, a specific level of energy generation is needed, endurance training allows for higher energy outputs to come from fat burning and improves duration by sparing carbs. Alternatively, training will also result in a potentially higher intensity level for a specific time period.

Typically, an aerobic training effect increases VO2max by as much as 25% in as little as 3 - 4 months of consistent training 3 - 4 times per week in the range of 60 - 85% maximum heart rate for 30 - 45 minutes per session. Fuel usage at the same absolute workload pre and post training (the post training workload is a lower relative intensity because VO2max has increased as a result of training) differs so that a greater reliance on fat for energy occurs. In addition, the greater reliance on fat for energy is derived largely from the greater utilization of intramuscular fat stores rather than peripheral sources.11,14 While this may appear counterproductive for fat loss, part two will discuss the importance of this development with regards to post-exercise effects and interval training and the relationship to bodyfat management.

[decypheredbeats]

part 3
What Effect Does Your Diet And Food Intake Have On All This?

Finally, diet and food intake need to be addressed in the context of fuel selection. Diet refers to the macronutrient composition that occurs in the range of two weeks prior to the exercise period. Unfortunately, many dietary studies typically involve a short adaptation period of as little as three days, although prior work suggests as many as 10 - 14 days are needed for complete adaptation to changes in macronutrient composition to fully manifest.18,19

Specifically, the macronutrient composition that matters is the amount of fat and carbs in the diet. Simply put, the less carbs ingested over time, the greater the reliance on fat burning.6 To achieve a faster response than changing the diet, specific glycogen depletion exercise routines can be employed.24,25,27 A sustained, reduced carb intake leads to a reduction in carb utilization at comparable work intensities. After four weeks of complete carb elimination, moderate intensity exercise can be performed with no reduction in endurance capacity, but two-thirds reduction in carb burning with a corresponding increase in fat burning.18

In other words, the less carbs you eat, the less your body will try to burn carbs while you are exercising. This means that you will naturally be burning more fat!

Food intake in the immediate pre-exercise period also affects fuel usage. Carb intake prior to exercise will result in release of insulin which retards lipolysis and fat utilization during subsequent exercise. Insulin in general promotes carb utilization throughout the body including working muscle and limits peripheral fat stores from releasing fats. Exactly how long after eating the system takes to return to baseline (defined as an overnight fast) depends on the specific meal. Studies with mixed meals suggest that effects can persist for 4 - 6 hours.8,15 Carb intake during exercise has a similar effect.5,9,10,20

Conclusion And Summary Of Points


Part I has served to introduce the basics of fuel selection and utilization during exercise along with the effects of training. Here are the main points:


There is a lot of confusion about how to really burn fat.
During exercise, your body will either burn fat (from your ugly fat stores or from inside the muscle), carbs or in some cases, protein.
Your body will decide which type to burn based on the intensity and duration of exercising, your type of diet and when you last ate, and how advanced of a trainee you are.
By following an exercise routine, you will burn more fat and calories even while you are at rest.
Fats require more oxygen to burn than carbs. This means that as exercise intensity is increased, there is a natural shift to burning more carbs because less oxygen is needed to extract the needed level of energy output to support that intensity.
The more instense the exercise is, the more carbs you will burn, in most cases.
Maximum fat burning rate occurs during moderate intensity at about 60 - 65% VO2max which corresponds to about 75% max heart rate for most people (this assumes an aerobically trained individual).
The less carbs ingested over time, the greater your body's reliance on fat burning.
Carb intake prior to exercise will result in release of insulin which stops or slows down the fat burning process.
However, the exercise period itself is only part of the story, the post exercise period also has an effect that is substantial. Understanding its role and its relation to intensity levels will serve to introduce the role of interval training and its application to body fat management in part II.

Note: This is part one, click here for part two!
click here for part three!

Reference List

1. Achten, J., M. Gleeson, and A. E. Jeukendrup. 2002. Determination of the exercise intensity that elicits maximal fat oxidation. Med. Sci. Sports Exerc. 34:92-97.
2. Aronne, L. J. 2001. Treating obesity: a new target for prevention of coronary heart disease. Prog. Cardiovasc. Nurs. 16:98-106, 115.
3. Bassett, D. R., Jr. and E. T. Howley. 2000. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med. Sci. Sports Exerc. 32:70-84.
4. Coyle, E. F. 1995. Substrate utilization during exercise in active people. Am. J. Clin. Nutr. 61:968S-979S.
5. Fritzsche, R. G., T. W. Switzer, B. J. Hodgkinson, S. H. Lee, J. C. Martin, and E. F. Coyle. 2000. Water and carbohydrate ingestion during prolonged exercise increase maximal neuromuscular power. J. Appl. Physiol 88:730-737.
6. Helge, J. W., P. W. Watt, E. A. Richter, M. J. Rennie, and B. Kiens. 2001. Fat utilization during exercise: adaptation to a fat-rich diet increases utilization of plasma fatty acids and very low density lipoprotein-triacylglycerol in humans. J. Physiol 537:1009-1020.
7. Hodgetts, V., S. W. Coppack, K. N. Frayn, and T. D. Hockaday. 1991. Factors controlling fat mobilization from human subcutaneous adipose tissue during exercise. J. Appl. Physiol 71:445-451.
8. Horowitz, J. F. and E. F. Coyle. 1993. Metabolic responses to preexercise meals containing various carbohydrates and fat. Am. J. Clin. Nutr. 58:235-241.
9. Horowitz, J. F., R. Mora-Rodriguez, L. O. Byerley, and E. F. Coyle. 1997. Lipolytic suppression following carbohydrate ingestion limits fat oxidation during exercise. Am. J. Physiol 273 :E768-E775.
10. Horowitz, J. F., R. Mora-Rodriguez, L. O. Byerley, and E. F. Coyle. 1999. Substrate metabolism when subjects are fed carbohydrate during exercise. Am. J. Physiol 276:E828-E835.
11. Hurley, B. F., P. M. Nemeth, W. H. Martin, III, J. M. Hagberg, G. P. Dalsky, and J. O. Holloszy. 1986. Muscle triglyceride utilization during exercise: effect of training. J. Appl. Physiol 60:562-567.
12. Klein, S., E. F. Coyle, and R. R. Wolfe. 1994. Fat metabolism during low-intensity exercise in endurance-trained and untrained men. Am. J. Physiol 267:E934-E940.
13. Lemon, P. W. and J. P. Mullin. 1980. Effect of initial muscle glycogen levels on protein catabolism during exercise. J. Appl. Physiol 48:624-629.
14. Martin, W. H., III, G. P. Dalsky, B. F. Hurley, D. E. Matthews, D. M. Bier, J. M. Hagberg, M. A. Rogers, D. S. King, and J. O. Holloszy. 1993. Effect of endurance training on plasma free fatty acid turnover and oxidation during exercise. Am. J. Physiol 265:E708-E714.
15. Montain, S. J., M. K. Hopper, A. R. Coggan, and E. F. Coyle. 1991. Exercise metabolism at different time intervals after a meal. J. Appl. Physiol 70:882-888.
16. Nicklas, B. J., E. M. Rogus, and A. P. Goldberg. 1997. Exercise blunts declines in lipolysis and fat oxidation after dietary-induced weight loss in obese older women. Am. J. Physiol 273:E149-E155.
17. Nieman, D. C., D. W. Brock, D. Butterworth, A. C. Utter, and C. C. Nieman. 2002. Reducing diet and/or exercise training decreases the lipid and lipoprotein risk factors of moderately obese women. J. Am. Coll. Nutr. 21:344-350.
18. Phinney, S. D., B. R. Bistrian, W. J. Evans, E. Gervino, and G. L. Blackburn. 1983. The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Metabolism 32:769-776.
19. Phinney, S. D., B. R. Bistrian, R. R. Wolfe, and G. L. Blackburn. 1983. The human metabolic response to chronic ketosis without caloric restriction: physical and biochemical adaptation. Metabolism 32:757-768.
20. Rauch, L. H., A. N. Bosch, T. D. Noakes, S. C. Dennis, and J. A. Hawley. 1995. Fuel utilisation during prolonged low-to-moderate intensity exercise when ingesting water or carbohydrate. Pflugers Arch. 430:971-977.
21. Romijn, J. A., E. F. Coyle, L. S. Sidossis, A. Gastaldelli, J. F. Horowitz, E. Endert, and R. R. Wolfe. 1993. Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. Am. J. Physiol 265:E380-E391.
22. Romijn, J. A., E. F. Coyle, L. S. Sidossis, J. Rosenblatt, and R. R. Wolfe. 2000. Substrate metabolism during different exercise intensities in endurance-trained women. J. Appl. Physiol 88:1707-1714.
23. Romijn, J. A., S. Klein, E. F. Coyle, L. S. Sidossis, and R. R. Wolfe. 1993. Strenuous endurance training increases lipolysis and triglyceride-fatty acid cycling at rest. J. Appl. Physiol 75:108-113.
24. Schrauwen, P., W. D. Lichtenbelt, W. H. Saris, and K. R. Westerterp. 1998. Fat balance in obese subjects: role of glycogen stores. Am. J. Physiol 274:E1027-E1033.
25. Schrauwen, P., W. D. Marken Lichtenbelt, W. H. Saris, and K. R. Westerterp. 1997. Role of glycogen-lowering exercise in the change of fat oxidation in response to a high-fat diet. Am. J. Physiol 273:E623-E629.
26. Spurway, N. C. 1992. Aerobic exercise, anaerobic exercise and the lactate threshold. Br. Med. Bull. 48:569-591.
27. Weltan, S. M., A. N. Bosch, S. C. Dennis, and T. D. Noakes. 1998. Preexercise muscle glycogen content affects metabolism during exercise despite maintenance of hyperglycemia. Am. J. Physiol 274:E83-E88.
28. Welty, F. K., E. Stuart, M. O'Meara, and J. Huddleston. 2002. Effect of addition of exercise to therapeutic lifestyle changes diet in enabling women and men with coronary heart disease to reach Adult Treatment Panel III low-density lipoprotein cholesterol goal without lowering high-density lipoprotein cholesterol. Am. J. Cardiol. 89:1201-1204.

Thanks,

[decypheredbeats]

part 4
In part I, the basics of exercise physiology were introduced to provide a framework for understanding the role of interval training in cardiovascular conditioning as well as body fat management. Part II will discuss two related concepts, the post-exercise period in terms of fuel usage and the underlying rationale for interval training along with its impact on cardiovascular training. Part III will discuss the actual mechanics of interval training and suggest specific protocols that have been proven to be effective by clinical research studies on trained athletes keeping in mind the intent of interval training as discussed below.

While fuel selection during exercise is primarily determined by the training status of the individual and the intensity of the exercise (see part I), in terms of weight management, the calories burned during exercise do not typically contribute substantially to a caloric deficit that is required for weight loss. Much of this is simply a numbers game. Mild to low-moderate intensity does not produce sufficient caloric expenditure to result in noticeable weight loss by itself.

Walking for example, typically will result in about 100 calories per mile expenditure; thus even a pace of 3.5 miles per hour (which is a brisk pace to maintain) will yield only 350 calories after one hour. Even if 100% of the calories were derived from fat, 10 hours would be necessary for 1 pound of body fat to be lost. Alternatively, higher intensities are limited by the duration that they can be sustained as well as a lower percentage of fat burned since carb burning increases with intensity (see part I).

The Post Exercise Period

Fortunately, the effect of exercise is not limited to simply the exercise period. Just as importantly is the effect of exercise on the post exercise period. This period can be examined from the standpoint of the immediate time frame after exercise to the remainder of the entire non-exercise time period. In terms of the overall impact on weight loss, the inclusion of exercise offers a clear benefit. Typically, with any caloric restriction diet to generate weight loss, over time the rate of weight loss tends to zero and weight plateaus.

This phenomena is usually due to a fall in the basal metabolic rate (resting metabolism) that is probably related to both a slight reduction in lean body mass that can accompany weight loss as well as hormonal adaptation to the lowered caloric intake.2 Exercise in this setting, even of mild intensity will promote preservation of lean body mass (assuming the calorically restricted diet is still able to supply sufficient protein taking into account increased protein required with physical activity) and prevent or reduce the fall in basal metabolic rate due to hormonal adaptation.2,19,20,22

Burn Fat For 3 Hours After Exercising?

Of more particular relevance however, to an already physically active group of individuals is the immediate post-exercise period. Studies have revealed that following aerobic exercise, there is a period of excess oxygen consumption relative to a similar period of time following rest.14 In other words, after an aerobic session, more oxygen is consumed during rest than would be if the exercise had not occurred.

Greater oxygen consumption implies that something is being burned, either fat or carb. In fact, most studies suggest that fat burning is providing the bulk of the excess oxygen consumption.12,14,15 In addition, the magnitude of the excess consumption is directly related to exercise intensity and duration.3,8,12,16-18 Thus, the higher the exercise intensity, the greater the degree of increased fat burning in the post exercise period which can extend for well over three hours following exercise.

The presumed mechanism for this effect is directly related to the fuel utilization during the exercise period. Recall that with increasing intensity from moderate to high, the percentage of energy supplied by fat burning declines (although the absolute decline is slower to trail off), while carb burning continues to increase. Also, carb sources in the body are quite limited. Depending on the exercise, one session can significantly reduce carb stores (glycogen) in the specific working muscles. Even with just rest, carb stores can be exhausted in 2 - 3 days if not replenished by food intake. Thus, following an exercise session that has depleted the muscle's glycogen content, the body will attempt to replenish these stores.

This means that carb uptake by the muscle will go to make glycogen, rather than burned for energy needs. However, even under resting conditions, the muscle still has basal metabolic energy requirements. To meet these requirements, the muscle will burn fat for fuel and this is the basis for increased fat burning in the post exercise period, since the conversion of carbs to glycogen in muscle will require some energy itself.

Clearly, following low intensity exercise, the muscle has little to do since neither intramuscular carb or fat stores have been significantly impacted. In addition, at low intensity, energy can be supplied by peripheral fat stores slowly releasing fat into the bloodstream. These fat stores are the most flexible since they can grow and contract as needed, but the rate of mobilization (or release) of fat from peripheral fat stores is limited.10 However, once moderate intensity is initiated, the situation changes dramatically.

Under moderate intensities, intramuscular fat stores must be tapped to support the level of energy generation, since the fat contribution from peripheral fat stores has reached its limit. In essence, moderate intensity can be viewed as the point where intramuscular fuel stores begin to be utilized. Carb burning will also increase linearly with intensity and the breakdown of intramuscular glycogen stores become significant during upper levels of moderate intensity.

Thus, following moderate intensity exercise, the two major intramuscular energy stores of fat (in the form of intramuscular triglyceride) and carb (in the form of glycogen) need to be replaced. Since carbs are limiting as discussed above, carbs, in the form of blood sugar, are diverted exclusively for glycogen replacement. Fat uptake is also increased and fuels energy needs as well as intramuscular triglyceride replacement. Endurance athletes develop increased intramuscular triglycerides as a part of training.9,11

This fat, both for energy needs as well as intramuscular triglyceride replacement, is derived from fat circulating fat in the bloodstream and comes from peripheral fat stores. Given that depletion of peripheral fat stores is limited in their rate of release of fat (the speed at which they can be depleted) continuing peripheral fat store depletion following exercise offers an attractive method to enhance bodyfat management. Desirable weight loss and bodyfat loss implies depletion of peripheral body fat stores.

The Intensity Of Exercise And How It Will Affect You

In summary, the intensity of exercise, regardless of the amount of fat burned during the exercise directly influences the amount of fat burned in the post exercise period. Since this fat is derived from peripheral fat stores, the higher the intensity and longer the duration that can be sustained, the greater the post-exercise fat burn that can be achieved. In essence, the combination of intensity and duration generate a carb and fat depleted state in the working muscle that shifts fuel metabolism towards fat burning to allow the muscle to return to its baseline levels of glycogen and intramuscular fat stores, ready for another round of exercise.

Sustained moderate intensity (in the range of 8 - 15 calories per minute) exercise can create this condition, but we will now turn our attention to another training modality, namely interval training, that will achieve this same effect within a shorter time period, and also contribute an added benefit from a cardiovascular training standpoint.

Interval training arose as means for endurance athletes to improve their performance capability. We have seen how VO2max measures the level of aerobic fitness; however, maintenance of an intensity at 100% VO2max can only be sustained for a few minutes because of the accumulation of lactic acid. Lactic acid, derived from carb burning, will gradually accumulate in the blood as a result of increased production in working muscle as intensity is increased.1


Calculate Your VO2max, Click Here!
This lactic acid must be cleared from the bloodstream to avoid high levels that upset the pH balance and cause the biochemical steps that generate energy from being disrupted because these steps function in a narrow pH range. Once in the blood, lactic acid can be removed a number of ways: 1) working muscles can buffer themselves against the drop in pH as a result of the acid load, 2) the liver can remove lactic acid from the blood and convert it back into glucose (since lactic acid is produced as a result of glucose breakdown, high levels of lactic acid imply that muscles are using a lot of glucose in the first place), 3) non-working muscles can take up lactic acid and burn it for fuel, conserving glucose for working muscles, and 4) the heart, which must always operate under aerobic condition can utilize lactic acid for fuel.

Lactic Acid

Lactic acid is produced during any exercise to some extent, but increases with intensity. Lactic acid accumulates in the blood, but remains relatively steady until a specific intensity (specific to the individual) is reached, at which time lactic acid levels rise uncontrollably resulting in muscle failure. This threshold level is referred to as the lactic acid threshold. Prior to the threshold level, the body's ability to remove lactic acid from the blood allows it to balance lactic acid production with removal. Above the threshold, the removal system has maxed out and can no longer keep pace with production.

The key for endurance performance lasting greater than a 45 - 60 minute time frame is to operate at an intensity that is below the lactic acid threshold5. Lactic acid threshold is somewhat individual, but has been shown to be a better predictor of athletic performance than overall aerobic fitness (VO2max).4,6,7 For example, athlete A with a lactic acid threshold at 71% VO2max could maintain a 60 minute intensity at 70% VO2max, while athlete B with a lactic acid threshold of 81% VO2max could maintain 80% VO2max during the same period. If their VO2max levels were equal (and they were the same size), athlete B would win a competition lasting an hour since he could sustain a greater intensity over the time period of the event.

How Do You Raise Your Lactic Acid Threshold?

The question then becomes how to train or raise your lactic acid threshold. This is the intent behind interval training. While performance at events lasting 60 minutes or longer may not be everyone's goal, the adaptations that occur with interval training are valuable beyond the improvement in athletic performance and contribute to body fat management in a productive manner. In addition, interval training can result in aerobic fitness improvements and maintenance with far less time investment than the more traditional increasing volume (meaning more time) work.

The essence of interval training is to work at an intensity level above one's lactic acid threshold, thus causing an increase of lactic acid that would result in muscle failure. This intensity is sustained for a duration that is somewhat less than the maximum possible time (that is, before failure occurs), typically on the order of several minutes. This is followed by a rest period or extremely light exercise to allow the body's systems to clear the lactic acid from the blood. The cycle is then repeated.

Thus, the body is exposed to a long cumulative total duration (longer than could be produced from continuous exercise) of elevated lactic acid and will learn to adapt to improving its ability to clear lactic acid from the blood. Cycling is typically repeated 8 - 15 times. If conditions are chosen appropriately, lactic acid levels will slowly climb and each cycle will become progressively more difficult. With this general type of protocol, the lactic acid threshold can be increased so that a higher intensity can be maintained for long periods (60 minutes or longer) without failure due to lactic acid levels.

For an endurance athlete, the value of lactic training is clear. With any program of aerobic training, there is typically an increase in VO2max of about 25% relative to sedentary levels. Greater gains can only be achieved with reductions in body weight (since VO2max is measured in terms of liters of oxygen consumed per minute per kilogram of body weight). After this initial gain which occurs over 3 - 5 months of aerobic training, further increases in training volume (that is longer training sessions), do not lead to further gains. To increase performance further, interval training allows for a higher level of intensity to be maintained under conditions relevant for athletic competition. While most sporting events do not operate at 100% VO2max, athletes typically perform at or just slightly above their lactic acid threshold.

Even for those interested in non-endurance activities, interval training can achieve several goals. First, interval training is relatively time efficient in terms of producing aerobic benefits.13 Second, interval training, along with other vigorous activities of comparable intensity have been associated with reductions in body fat, specifically in terms of a reduction in skinfold thickness.21

While the physiologic basis for this effect has not been identified, the likely effect is a combination of post exercise fat burning as discussed above, along with secretion of growth hormone that occurs during intense physical activity.23 Growth hormone besides its obvious effects on muscle mass is also known to produce a lipolytic effect that would promote a loss of fat.

[chris davis 200]

I am gonna be starting my HIIT routine today.

I have been doing the traditional 40 min running thing But i have just been looking into this and it seems like it is for me so that is great!

THANKS GUYS!

One question - how does this training method work with a low carb diet??

cheers
chris

[decypheredbeats]

Conclusion


Finally, interval training can improve and raise the lactic acid threshold which permits a higher intensity of sustained aerobic activity for longer periods of time. Thus, for a specific time period allocated for aerobic exercise, a higher intensity level can be utilized for greater caloric expenditure.
Part II has discussed the importance of the post-exercise period in terms of bodyfat management and its relation to exercise intensity. The concept of interval training was introduced and detailed to highlight the value in an overall aerobic conditioning program. Finally, the confluence of several factors suggests that the addition of interval training provides special benefits with regards to bodyfat management because of the intensity level and the post-exercise period.

With the digital bodyfat measuring device you can, measure you body fat by yourself in a few seconds with superior clinical accuracy!
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Part III will discuss various interval training protocols that can be utilized under a wide variety of conditions. Given the intensity of this type of training, some protocols are simply not suitable for all training regiments and care must taken to identify appropriate protocols. A wide range of protocols will be presented to offer options for nearly everyone.

Note: This is part two, click here for part one!
click here for part three!

Reference List

1. Antonutto, G. and P. E. Di Prampero. 1995. The concept of lactate threshold. A short review. J. Sports Med. Phys. Fitness 35:6-12.
2. Astrup, A., P. C. Gotzsche, W. K. van de, C. Ranneries, S. Toubro, A. Raben, and B. Buemann. 1999. Meta-analysis of resting metabolic rate in formerly obese subjects. Am. J. Clin. Nutr. 69:1117-1122.
3. Bahr, R. 1992. Excess postexercise oxygen consumption--magnitude, mechanisms and practical implications. Acta Physiol Scand. Suppl 605:1-70.
4. Bassett, D. R., Jr. and E. T. Howley. 2000. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med. Sci. Sports Exerc. 32:70-84.
5. Billat, L. V. 1996. Use of blood lactate measurements for prediction of exercise performance and for control of training. Recommendations for long-distance running. Sports Med. 22:157-175.
6. Billat, L. V. and J. P. Koralsztein. 1996. Significance of the velocity at VO2max and time to exhaustion at this velocity. Sports Med. 22:90-108.
7. Coyle, E. F. 1999. Physiological determinants of endurance exercise performance. J. Sci. Med. Sport 2:181-189.
8. Gore, C. J. and R. T. Withers. 1990. Effect of exercise intensity and duration on postexercise metabolism. J. Appl. Physiol 68:2362-2368.
9. Hardman, A. E. 1998. The influence of exercise on postprandial triacylglycerol metabolism. Atherosclerosis 141 Suppl 1:S93-100.
10. Hodgetts, V., S. W. Coppack, K. N. Frayn, and T. D. Hockaday. 1991. Factors controlling fat mobilization from human subcutaneous adipose tissue during exercise. J. Appl. Physiol 71:445-451.
11. Klein, S., E. F. Coyle, and R. R. Wolfe. 1994. Fat metabolism during low-intensity exercise in endurance-trained and untrained men. Am. J. Physiol 267:E934-E940.
12. Laforgia, J., R. T. Withers, N. J. Shipp, and C. J. Gore. 1997. Comparison of energy expenditure elevations after submaximal and supramaximal running. J. Appl. Physiol 82:661-666.
13. Laursen, P. B. and D. G. Jenkins. 2002. The scientific basis for high-intensity interval training: optimising training programmes and maximising performance in highly trained endurance athletes. Sports Med. 32:53-73.
14. Maehlum, S., M. Grandmontagne, E. A. Newsholme, and O. M. Sejersted. 1986. Magnitude and duration of excess postexercise oxygen consumption in healthy young subjects. Metabolism 35:425-429.
15. Medbo, J. I. and E. Jebens. 2002. Leg gas exchange, release of glycerol, and uptake of fats after two minutes bicycling to exhaustion. Scand. J. Clin. Lab Invest 62:211-221.
16. Phelain, J. F., E. Reinke, M. A. Harris, and C. L. Melby. 1997. Postexercise energy expenditure and substrate oxidation in young women resulting from exercise bouts of different intensity. J. Am. Coll. Nutr. 16:140-146.
17. Rauch, L. H., A. N. Bosch, T. D. Noakes, S. C. Dennis, and J. A. Hawley. 1995. Fuel utilisation during prolonged low-to-moderate intensity exercise when ingesting water or carbohydrate. Pflugers Arch. 430:971-977.
18. Sedlock, D. A., J. A. Fissinger, and C. L. Melby. 1989. Effect of exercise intensity and duration on postexercise energy expenditure. Med. Sci. Sports Exerc. 21:662-666.
19. Stefanick, M. L. 1993. Exercise and weight control. Exerc. Sport Sci. Rev. 21:363-396.
20. Thompson, J. L., M. M. Manore, and J. R. Thomas. 1996. Effects of diet and diet-plus-exercise programs on resting metabolic rate: a meta-analysis. Int. J. Sport Nutr. 6:41-61.
21. Tremblay, A., J. A. Simoneau, and C. Bouchard. 1994. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism 43:814-818.
22. van Dale, D. and W. H. Saris. 1989. Repetitive weight loss and weight regain: effects on weight reduction, resting metabolic rate, and lipolytic activity before and after exercise and/or diet treatment. Am. J. Clin. Nutr. 49:409-416.
23. Wideman, L., J. Y. Weltman, M. L. Hartman, J. D. Veldhuis, and A. Weltman. 2002. Growth hormone release during acute and chronic aerobic and resistance exercise: recent findings. Sports Med. 32:987-1004.

Thanks,

[decypheredbeats]

the article I just posted was written by

Michael Kurilla MD-PHD

yeah its like that.......

[decypheredbeats]

Originally posted by chris davis 200
I am gonna be starting my HIIT routine today.

I have been doing the traditional 40 min running thing But i have just been looking into this and it seems like it is for me so that is great!

THANKS GUYS!

One question - how does this training method work with a low carb diet??

cheers
chris

I eat less then 100 grams of carbs a day.

I prefer to let my body use fat as an energy source.
considering HIIT is geared towards using fat for energy, then Id say it would work pretty good on a low carb diet. Just keep your fat and protien high.

One thing I try to do is keep my carb/ protien meals before noon. Its been shown that Insulin levels are peaked in the mornign and decrease threwout the day, making carbs a better source of energy in the morning and fats for later in the day.

BTW I train with very high intensity for an hour 2x a day for 6 days a week. I have very low BF, always have always will, SO I do not know personally how its feel to switch from deoing moderate intensity to high intensity, Ive alway trained with high intensity.....Maybe someone else could help you here.