Okay, I'm gonna disagree here. I think high intensity interval training is best for burning fat. Just my opinion but it is after reading studies and articles such as this. Just something to ponder. This is very long but worth the reading, IMO.
Intervals for Fitness and Fat Loss
(Q & A with Dr. Pat O'Shea)
"Short-term intense interval training is highly effective in altering the ratio of lean body mass to fat without compromising muscle mass." Pat O'Shea, Ed.D.
For two months now we've been challenging the common belief that low intensity, long duration exercise is best for fitness and fat loss. We've shown that very brief and very hard interval training is amazingly effective in developing both aerobic and anaerobic capacity - and far superior for fat loss. (See articles #10 and 11)
Now, it's time to step back and ask where intense intervals fit in the total spectrum of fitness training. What's best for endurance athletes? Bodybuilders? Older athletes? For total conditioning?
Who better to go to for a broader perspective on interval training than Patrick J. O'Shea, Ed.D, Professor Emeritus of exercise and sports science at Oregon State University? Not only has Pat been a student of sports physiology for four decades, he has excelled as an Olympic and power lifter, a cyclist, a mountain climber, a skier and a coach.
What's he doing now? Pat tells us he plans to compete in cycling and bowling next August at the Nike World Masters Games to be held in Portland, Oregon.
Who better indeed?
(For more information on Dr. O'Shea see "Guru of Quantum Strength," article #5 on this site).
We prevailed on Dr. O'Shea to review our articles, "Forget the Fat Burn Zone" and "In Search of the Ideal Aerobics Routine." We then asked him some specific questions designed to focus his vast knowledge and experience on the subjects we've been discussing.
We were very interested in what Pat had to say, and believe readers will be informed as well. Enjoy. (Italicized emphasis in the answers is ours.)
Bass: You've used intervals in your own training and also published research on the subject. Were you surprised that Dr. Tabata's group found that only 6-8 very hard 20 second intervals with 10 second rest periods substantially improved both aerobic and anaerobic capacity?
O'Shea: No, not at all. Dr. Tabata's study is excellent and his findings confirm previous studies that have looked at the effects of intense interval training on aerobic and anaerobic performance. (See O'Shea, John P., Bicycle Interval Training for Cardiovascular Fitness. The Physician & SportsMedicine 10:156-162, October, 1982). Coaches and athletes need to understand however, that short-term intense interval training has very limited application to long-distance events such as marathon running and the Tour de France. Long distance endurance athletes need efficient "fat burning" bodies. Their muscles must be trained to utilize energy from free fatty acid oxidation while conserving the limited stores of glycogen which are necessary for nerve and brain function. (Nerves and the brain derive energy only from glycogen - not fat.)
Long-term aerobic training increases the enzymes associated with fat metabolism and trains the working muscles to utilize oxygen more efficiently. The result is an increase in oxygen uptake capacity of the trained muscles, and not in the untrained. This is important for athletes to know as it involves the principle of specificity. For example, competitive swimmers develop high aerobic capacity specifically for swimming. Out of the water their aerobic conditioning is not transferable to running, because different sets of muscles are involved which are aerobically untrained.
To train, smart athletes need at minimum an elementary understanding of the cardiovascular and circulatory processes leading up to aerobic metabolism within muscle. While the following description is highly simplified, it does provide an overall picture of the steps involved. Initially, it begins with the ability of the lungs to take up and then unload oxygen in the blood; the ability of the red blood cells to pick up the oxygen as it flows through the lungs; the ability of the heart to pump a large volume of blood (stroke volume) to the working muscles; and finally, but most critical, the efficiency of the working muscles to take up oxygen from the blood and use it for oxidative energy production. Physiologically, this whole process is what cardiovascular fitness is all about.
Another important consideration in understanding aerobic and anaerobic metabolism is that muscles differ in their ability to utilize oxygen. Slow twitch muscles are noted for their endurance and have the ability to use large quantities of oxygen required for fat metabolism during aerobic exercise. Fast twitch muscles are the strength and power producing muscles. They are good for explosive bursts of anaerobic energy for sprinting, jumping, lifting and interval work. However, they fatigue fast and are not efficient fat burners. Glycogen is their main source of energy during intense work making them ideal for anaerobic exercise lasting up to three minutes. Exercise lasting longer than three minutes is aerobic.
The bottom line is that short-term intense interval work is not designed to train the body to become an efficient fat burner as is required for long-distance endurance activities. However, for sprint cycling or running (up to 400 meters) intense interval training definitely offers major physical benefits. In the overall scheme of training for athletes participating in stop and go power sports (e.g., football, basketball, ice hockey and gymnastics) short-intense interval work has a major role to play in maximizing performance.
Q. Exercise physiologists have traditionally believed that volume, not intensity, is the key to successful aerobic training. Where do you come down on the volume versus intensity question?
A. My position is that in order to become a successful endurance athlete (cyclists, runner, etc.) one must cross-train. A training program based on volume, such as running a hundred miles a week, will not maximize aerobic capacity or develop a high anaerobic capacity. What is required is a cross-training program encompassing aerobic and anaerobic workouts. The aerobic workout is LSD (long-steady distance) running or cycling at just below the anaerobic threshold (or race pace). During an LSD workout the heart rate is usually 75-85 percent of the age related maximum. (The only time V02max can be utilized to set or measure intensity is in a human performance lab where it can be monitored.) Anaerobic running, on the other hand, consists of interval training at distance ranging from 200m to 800m, and for cycling 800m to 1500m, at a heart rate of 90-95 percent of maximum. Following high intensity interval workouts there needs to be several days of light recovery workouts of low to medium intensity.
Also, both aerobic and anaerobic energy systems can be effectively cross-trained in a single workout session, which should closely duplicate the physiological race demands of volume and intensity. For example, in a 100 mile bike race, which encompasses both high work volume and intensity, it is imperative that the cyclists focus on maximizing aerobic and anaerobic conditioning. Typically, in such a race the cyclist encounters varying terrain from flats to rolling hills and breakaways and attacks by other riders. Aerobic power is essential for sustaining a hard fast pace on the flats, while anaerobic power plays key roles in initiating a breakaway or not getting dropped when one occurs; chasing down a break or lead group; attacking and accelerating on hills; and sprinting to the finish. Anaerobic power and explosive strength are the two factors which allow the cyclists to control the race. Applying strategy that calls for numerous breaks and attacks on hills, an elite cyclist will wear down weaker riders and psychologically destroy them. It is imperative then that a cyclist's long-range training program include lots of cross-training workouts that call for volume (distance) riding interspersed with speed work and interval hill repeats.
Q. In your book Quantum Strength and Power Training (Gaining The Winning Edge) (1996), you wrote: "Statistically, there is a close relationship between V02max and lean body mass." Were you surprised when the Tremblay group - challenging the common belief that low intensity, long duration exercise is best for fat loss - found that short intervals (30-90 seconds) produced substantially more fat loss for each calorie burned exercising? Why?
A. No, I was not surprised by Tremblay's findings showing that low intensity, long duration exercise is not as effective as short intense intervals in reducing body fat. It is relatively easy to explain why this is so.
During strenuous exercise, the rate of metabolism rises, going to about 15 times the basal metabolic rate (BMR) and even higher during intense interval work. For example, running 5 mi/hr the oxygen uptake required is 28 ml 02/min/kg of body weight with 3.7 cal/hr./lb burned, while a short burst of intense interval work may require 100 ml 02/min/kg with 13.8 cal/hr/lb burned. By maintaining the high level of training over a 5 or 6 week period one would expect a significant increase in the ratio of lean body mass to fat. Over a three month period you would be RIPPED like never before.
Intense interval work utilizes a greater percent of the body's muscles, both slow and fast twitch. Also, performing high intensity work places added energy demands on the respiratory system, cardiovascular system and nervous system. Thus more fat and glycogen are burned to support the expanding energy demands of the body during - and after - intense exercise. In other words, the cost of short intense interval exercise is very high in terms of energy demands in comparison to low intensity aerobic exercise. What's more, while at rest trained active muscles burn more fat night and day, contributing to further fat loss.
Q. I'm preparing for the treadmill test at the Cooper Clinic. (They increase the grade one percent every minute up to 25%, and then the speed, to exhaustion.) In the past, I've lasted between 28 and 29 minutes. Would Tabata's 20 second intervals on the Air-Dyne, rower and treadmill be a good way to prepare? Should I add some training that more closely parallels the test protocol?
A. The key in preparing for a treadmill test is concentrating on improving anaerobic power - i.e. pushing back the anaerobic threshold which is the point at which lactic acid begins to accumulate at a high rate in the blood. This is an indication that oxygen uptake at the muscle cell level can not keep up with the work demands. Once this threshold has been exceeded your V02max is calculated.
Training with an Air-Dyne or rower to raise your anaerobic threshold for the treadmill test is going to produce very limited results. It is not specific enough to the test. Hard interval repeats of 2-3 minutes duration on a treadmill, stairmaster, hill, or stadium steps will provide the best results. These training activities not only develop anaerobic power, but also strong quadriceps that are required to run on a grade.
Q. Is there a lesson here for athletes preparing for specific events?
A. Yes, there is a very important lesson to be learned and understood. While the specificity principle is the cornerstone of athletic training, variety or diversity in training is required to achieve the highest level of total conditioning. Training variability encompasses the concept of cross-training. It allows for the simultaneous training of multiple physiological variables (e.g., aerobic and anaerobic, power, strength, speed, and power) that contribute to peak athletic performance in all sports.
Q. As I point out in Ripped 3, bodybuilders have a problem using aerobics for fat loss, because endurance exercise can work against gains in muscle size. Would the Tabata protocol of high-intensity intervals be good for bodybuilders who want to preserve muscle mass while losing fat?
A. The answer is definitely a big yes. As discussed in question 3, short-term intense interval training is highly effective in altering the ratio of lean body mass to fat without compromising muscle size. Intense interval work is an excellent way of losing weight while simultaneously getting ripped for peak contest shape.
Competitive bodybuilders will find another highly productive method of interval training outlined in my book Quantum Strength & Power Training, Chapter 10, "Interval Weight Training (1WT)". It is one of the most challenging, intensive methods of cross-training yet devised for muscular endurance and anaerobic power. IWT is heavy-duty quantum training - physically tough and mentally demanding. If you are a serious bodybuilder and like a new challenge try it for several weeks. The results will amaze you.
Q. What about healthy older people who want to be lean and fit? Would it be advisable for them to do short, hard intervals?
A. The answer is yes and no. First, it is not advisable for anyone to attempt interval training without first getting medical clearance preferable from a sports medicine physician who has a clear understanding as to the physical demands to be encountered. For any person having coronary heart disease the answer must be a big no. For a healthy person having a reasonably good level of aerobic fitness - (i.e., a minimum V02max of 50ml/kg/min) there should be no problem. However, as an added safety measure, it would be a good idea to take a treadmill stress test to be sure that there are no cardiac abnormalities.
For best results and safety, the intensity of the interval workouts should be set using a percent of one's age-related maximum heart rate. An easy method of determining maximum exercise heart rate for interval work is to subtract your age from 220 and then use 90-95 percent of that figure. For a 40 year old individual the interval exercise target heart rate would be 171 (220 - 40 = 180 x .95 = 171). Remember too, interval training is very stressful on the body and joints and should not be done more than two times a week. Yes, young athletes are more resilient than master age-group athletes. They recover quicker and more fully between workouts which allows them to do interval training with greater frequency.
In Search Of The Ideal Aerobics Routine
"[Six to 8 very hard 20 second intervals with 10 second rest periods] may be one of the best possible training protocols...."
..................Izumi Tabata, Ph.D., National Institute of Health & Nutrition, Tokyo, Japan
Why does this very short interval workout ( it is also discussed in article #10, Forget The Fat-Burn Zone) work so well? Why does this protocol substantially improve both aerobic and anaerobic capacity? Why is that a surprise? Is there a lesson in this for bodybuilders and others interested in both strength and endurance?
Overload and Specificity
The answers to the first three questions lie mainly in the principles of overload and specificity. The overload principle says that training adaptations come about when the body is subjected to unaccustomed stress. Specificity says the adaptation depends on the nature of the overload imposed. In other words, specific exercise overload brings about specific training effects. For example, strength training induces specific strength (anaerobic) adaptations and endurance exercise elicits specific endurance (aerobic) adaptations - with essentially no interchange between the two types of training. As you'll see, these two principles explain both why the single protocol was not supposed to cause both aerobic and anaerobic improvements and, interestingly, why both types of adaptations did in fact occur.
As a follow-up to the study discussed in article #10, Forget The Fat-Burn Zone, Dr.Tabata and his colleagues conducted a second study "to evaluate the magnitude of the stress on the aerobic and the anaerobic energy release systems" of the high intensity protocol used in the previous study and, additionally, of a second interval protocol. (Medicine and Science in Sports and Exercise (1997) 29, 390-395) The two protocols in the follow-up study differed in three ways: interval duration, intensity and rest between bouts.
As in the previous study, young male members of college varsity teams exercised on stationary bicycles. The two protocols were given the catchy names 1E1 and 1E2. Protocol 1E1 was the same as before: following a 10 minute warm-up, each subject did one set of 6-7 bouts of 20 seconds at approximately 170% of the subject's maximal oxygen uptake (VO2max), with 10 second rest periods, to exhaustion. The 1E2 group did 4-5 bouts of 30 seconds at 200% of VO2max, with 2 minute rest periods, to exhaustion. For each protocol, the criteria for exhaustion was that the subject was unable to maintain a pedaling speed of 85 rpm. Expired gas was collected continuously every 10 seconds to measure the oxygen uptake. As in the earlier study, accumulated oxygen deficit was used to measure anaerobic energy release.
The results were eye-opening. The 1E1 protocol taxed both aerobic and anaerobic capacity significantly more than the 1E2 protocol. The peak oxygen uptake during the last 10 seconds of 1E1 was "not statistically different from the subjects' VO2max." But the peak oxygen uptake at the end of 1E2 "was much less than the VO2max." Likewise for anaerobic output: For 1E1, accumulated oxygen deficit was essentially 100% of the subjects anaerobic capacity, but for 1E2 it was only 67%. In short, the 20 second intervals, with 10 seconds rest, overloaded both aerobic capacity and anaerobic capacity to the max, while the longer and harder interval protocol, with two minute rest periods, did not. In both respects, the stress produced by 1E2 fell well short of maximum.
This, of course, is why 1E1 improved both aerobic and anaerobic fitness. In the words of the researchers, "For most physical properties the more demanding the training is the greater the improvement of the property." If you overload aerobic capacity and anaerobic capacity maximally, you should get maximum improvement in both capacities.
Yes, this study is good news for the many athletes engaged in high-intensity sports which demand both aerobic and anaerobic fitness and those who strive for total fitness. But why did 1E1 work so much better than 1E2? (The explanation is a little long, so bear with me.)
First, it has long been known that intervals are an effective training method. With intervals, more total work can be accomplished at a given intensity than when exercising continuously. For example, few people can run a 4 minute mile, but many more can complete a mile in 4 minutes of actual running, if the distance is broken into segments or intervals separated by rest periods.
The Surprise
Exercise physiology textbooks tell us that work interval duration and intensity, and the length of the rest periods - the variables studied by Dr. Tabata - must be carefully adjusted to meet the specific requirements for different performances. As indicated above, adaptations are specific to the speed and duration of workout. Generally, short hard intervals with long rest periods are recommended to improve anaerobic capacity; and many sets and repetitions of longer less intense intervals with short rest periods are suggested to overload the aerobic system.
In other words, the interval protocols traditionally prescribed to engage the aerobic system are usually quite different from those suggested for anaerobic training. This is simply an application of the specificity principle, with little or no interchange predicted between the two types of training.
That, of course, is why it was a surprise when Dr. Tabata's earlier study found that the 1E1 protocol (20 second bouts with 10 seconds rest) "may be optimal with respect to improving both the aerobic and anaerobic energy release systems." As readers of my earlier article will remember, Dr. Tabata told Dick Winett in a personal communication "that the rate of increase in VO2max [14% in only 6 weeks] is one of the highest ever reported in exercise science." Recall also that anaerobic capacity increased by a whopping 28%.
The Key Factor
Like Goldilocks' porridge, it seems that Dr. Tabata has come upon an interval protocol that is "just right." As shown in the follow-up study, 1E1 overloads both aerobic and anaerobic capacity maximally - with the predictable result that both systems benefit optimally. As the original research report stated: "1E1 may be one of the best possible training protocols...."
But why? Why did the 1E1 protocol stress both aerobic and anaerobic capacity maximally, when the more intense (200% Vo2max vs. 170%) and longer (30 seconds vs. 20-s) bouts of the 1E2 protocol did not? The researchers believe the key factor was the difference in the rest periods.
The relatively long 2 minute rest periods in 1E2 allowed oxygen uptake to fall considerably and, therefore, when the next exercise bout started there was a delay before the oxygen uptake increased and began again to approach maximum. On the other hand, the short 10 second rest periods in 1E1 allowed only slight recovery, and therefore oxygen uptake increased in each succeeding bout, reaching maximum capacity in the fiinal seconds of the last bout. The same was true for anaerobic energy release. The long rest periods in 1E2 stopped the buildup of lactate and allowed the resynthesis of phosphocreatine (see creatine article on this website) to occur. Again, the short rest periods in 1E1 caused the oxygen deficit to continue building from rep to rep, reaching maximum anaerobic capacity at the end of the exercise.
Dr. Tabata's 1E1 protocol may not be perfect, but he and his colleagues seem to have found a sweet spot where aerobic and anaerobic capacity peak simultaneously.
The Lesson
It seems to me that the lesson in this for bodybuilders and other fitness enthusiasts is that more aerobic training is not necessarily better. Many athletes and coaches believe that gains in aerobic endurance are proportional to the volume of training. In fact, noted exercise physiologists Jack H. Wilmore and David L. Costill, in their text Physiology of Sport and Exercise (Human Kinetics, 1994), state flatly: "Because volume is the key to successful aerobic training, [athletes] must perform a large number of [intervals]." (They do caution that there's an upper limit.)
Importantly, the two studies by Dr. Tabata's group strongly suggest that volume is not necessarily the key.
Recall that the moderate-intensity group in the first study trained 5 days per week at 70% of VO2max, 60 minutes each session, and increased aerobic capacity only 10% and anaerobic capacity not at all. And in the second study, the 1E2 group exercised both harder and longer; they did more total work than the 1E1 group. Clearly, these studies indicate that gains are not necessarily dependent on volume or total work performed.
If the goal is improved aerobic and anaerobic capacity, the Tabata research suggests that intensity, carefully applied to produce maximum overload - not volume - is the key to success.
At A Price
Progress by this method, of course, comes at a price. Tabata's 1E1 protocol is physically and psychologically taxing. It requires considerable motivation. Dr. Tabata, in a personal communication, warned Dick Winett: "This protocol [was] invented to stress the cardiovascular systems of top Japanese [speed] skaters who got medals in the Olympic games. Therefore, the protocol is very tough. The subjects lay down on the floor after the training." Tabata wondered how many people would "feel eager to do this type of exercise."
Still, for those who are fit and healthy (if you have questions about your health by all means check with your doctor) and up to the challenge, Tabata offered this encouragement: "From the theoretical point of view, the higher the oxygen uptake obtained in a specific training protocol, the higher the improvement of VO2max."
Good luck.
Q. Is it true that low-intensity aerobic exercise is the best way to lose fat?
A. No. It is true that the body's reliance on carbohydrate as an energy source increases as intensity increases; the higher the exercise intensity, the greater the use of carbohydrate stores. This is the basis for the often heard recommendation to keep exercise intensity low in order to maximize the loss of body fat, or to "stay in the fat-burn zone." I don't buy it and neither should you.
Professors Jack H.Wilmore (University of Texas at Austin) and David L. Costill (Ball State University, Muncie, Indiana) expose the fat burn fallacy in their beautifully designed textbook Physiology of Sport and Exercise (Human Kinetics, 1994): "Low-intensity aerobic activity does not necessarily lead to a greater expenditure of calories from fat. More importantly, the total caloric expenditure for a given period of time is much less when compared with high-intensity aerobic activity."
To illustrate they give the example of a 23-year-old woman who exercised for 30 minutes at 50% of her VO2 max on one day, and for 30 minutes at 75% on another. The total calories from fat were the same - in both sessions she burned 110 calories of fat. Most importantly, however, in the higher intensity workout she expended about 50% more calories for the same time period, 220 total calories for the 50% intensity workout and 332 for the 75% session.
For an average 40-year-old male the calories from fat would be about 145 in both sessions, but the total calories burned during the higher intensity workout would be 435 compared to only 290 in the low-intensity session, again 50% more. That's a big difference and over time the higher-intensity sessions will produce far more fat loss.
I asked Dr. Robert Robergs, director of the Center for Exercise at the University of New Mexico and co-author of EXERCISE PHYSIOLOGY: Exercise, Performance and Clinical Applications (Mosby, 1997), how the fat burn fallacy got started. He isn't sure but believes people simply like the word "easy." He thinks they grab on to the idea, because it makes easy training "more readily acceptable." Nevertheless, he says, "You can't convert a relative contribution to an absolute value; it's the total amount of calories [burned] that's most important."
"There is another issue too," Robergs adds, which makes the intensity of the workout important for fat loss. A more intense approach, he explains, "is more conducive to improving the muscle's ability to use fat." The more fit you become, the more likely you are to use fat as fuel. "When you become more fit you are just better able to metabolize fat for any given activity you do," Robergs stresses. In other words, you not only burn more calories during workouts, you burn more fat 24 hours a day
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My contention at the time (the later infomation from Dr. Robergs was not there yet) was that if in both examples the same fat calories are burnt, then the excess from higher intensity is precious glycogen and LBM! We finally concluded that a faster metabolism, burning more calories, potentially fat caloires, for hours after the exercise bout was beneficial!
I’d like to present a research study relating the effects of a HIIT (High Intensity Interval Training) cardio program versus a more traditional cardio (TC) program.
One group (TC) performed uninterrupted cycling on a stationary bike for 20 weeks. They started at 30 minutes; 4 days per week and at the end of 20 weeks had increased to 5 days per week at 45 minutes.
Exercise intensity was 60% MHR at the beginning of the study and by the end it had increased gradually to 85% MHR
TC performed an average of 90 cardio sessions over the 20-week period
Over the 20 weeks the TC group lost an average of 5 points on the sum of their skin folds or about 1% bodyfat. The HIIT group performed the following cardio program for 15 weeks (5 weeks less than the TC group)
Twenty-five 30-minute sessions of Moderate Intensity Cardio (70% MHR)
Thirty-Five HIIT sessions
Intensity of HIIT sessions was increased by 5% every three weeks
The HIIT sessions were broken down as follows:
19 short interval sessions consisting of an easy 5-minute warm-up at 50%, then 10-15 sets of short interval work (15-30 seconds each followed by a one minute rest)
17 longer interval sessions consisting of an easy 5-minute warm-up, then 4-5 sets of 60 - 90 second interval work each followed by the same length rest period. Note: Rest periods are not stop pedaling, but pedaling at an intensity level of 50-60% MHR
HIIT performed a total of 60 sessions over the fifteen-week period. The HIIT group lost an average of 14 points on the sum of their skin folds or about 3% bodyfat
The caloric expenditure for the (TC) group was actually more than double that of the HIIT group, yet the HIIT group lost nearly triple the amount of fat!
Tremblay, A, et al: Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism 43, No 7:814-818, 1994
In Summary:
Cardio is good for your health! But as practiced by most bodybuilders it is not necessarily best for fat loss or keeping your lean muscle mass. Forty-five minutes to an hour of low intensity cardio often will cause you to lose muscle. Yes, it’s true that during low intensity cardio more fat (not necessarily bodyfat but lipids in the blood and from the muscle as well) is burned as fuel than at higher intensity levels. However, we have found that it’s not just during, but also after cardio that fat may be burned. High intensity cardio seems to be better suited to the competitive bodybuilder than the more popular low intensity method.
Here’s why:
A favorable hormonal environment is created by high intensity cardio including a growth hormone response
High intensity cardio causes the “fat burning “ response to last for hours after completion of your cardio session
High intensity cardio takes less time and yields better results.
What NOT to eat after exercise if you want to lose fat
If you really want to accelerate fat loss, make sure to ignore the popular recommendation to fill up with carbohydrates after you exercise.
A team of researchers from Canada report that a high carbohydrate meal immediately after a workout will depress the effect that exercise normally has on your metabolic rate. After you finish training, your body continues to burn more fat calories -- sometimes for up to 48 hours. However, a high carbohydrate meal immediately following a workout appears to "dampen" this natural rise in fat burning.
A group of eight men exercised on a treadmill for 60 minutes. Immediately after the workout, they consumed a milk shake that replaced the calories they burned during exercise. The men spent the next three days in a respiratory chamber, which allowed scientists to measure their metabolic rate (the things some people will do for money!).
Here's what happened during the three days in the respiratory chamber:
Group Fat grams burned Calories burned daily
No exercise 202 grams 2016
Exercise 209 grams 2040
As you can see, there was very little difference between the exercise and no-exercise groups, both in terms of daily caloric expenditure and the total number of fat grams burned.
Remember, the main factor that determines your rate of fat loss is energy balance -- the number of calories you take in must be less than the number of calories you expend. However, according to lead researcher Isabelle Dionne, "the avoidance of energy and substrate compensation after exercise is of major importance to maintaining a negative energy balance".
In other words, if you want to speed up fat loss, avoid a big carbohydrate meal straight after you finish training.
Reference
Dionne, I., Van Vugt, S., & Tremblay, A. (1999). Postexercise macronutrient oxidation: a factor dependent on postexercise macronutrient intake. American Journal of Clinical Nutrition, 69, 927-930
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& then I'm really bored! Fortunately I'm equipped today with a good book to combat boredom!
