In
Part 1 of this series Alan Aragon took an in-depth looks at the Low Intensity Fat Burning Zone. Part 2 focuses on a concept that often goes hand-in-hand with low intensity cardio training - Fasted cardio.
Similar to Part 1, this article is highly research intensive. Hang in there and we'll pull everything together later this week!
False Hopes For Fasted Cardio:False Hopes The b
andwagon is lead by blind horses Many trainees pigeonhole weight training as an activity exclusively for building muscle, and cardio exclusively for burning fat. On the contrary, weight training can yield very similar results to cardio of similar intensity when 24-hour energy expenditure and macronutrient oxidation is measured [1].
The obvious advantage of weight training is the higher potential for lean mass and strength gains. In the bodybuilding context, cardio should be viewed as merely an adjunctive training mode to further energy expenditure and cross-complement the adaptations specific to weight training.
As far as cardio being absolutely necessary for cardiovascular health, well, that depends upon the overall volume and magnitude of your weight training - another topic for another time.
Chaos theory strikes again On the surface, it seems logical to separate carbs from cardio if you want a maximal degree of fat oxidation to occur during training. But, there's the underlying mistake - focusing on stored fuel usage during training instead of focusing on optimally partitioning exogenous fuel for maximal lipolytic effect around the clock.
Put another way, it's a better objective to coincide your carb intake with your day's thermic peaks, where insulin sensitivity and lean tissue reception to carbs is highest. For some reason, this logic is not easily accepted, nor understood. As we know, human physiology doesn't always cooperate with logic or popular opinion, so let's scrutinize the science behind the claims.
Let the Research SpeakCarbohydrate ingestion during low-intensity exercise reduces fat oxidation As far as 3 decades back, Ahlborg's team observed that carb ingestion during low-intensity exercise (25 - 45% VO2 max) reduced fat oxidation compared to fasted levels [2]. More recently, DeGlisezinski's team observed similar results in trained men at 50% VO2 max [3].
Efforts to determine the mechanism behind this phenomenon have been made. Coyle's team observed that at 50% VO2 max, carbohydrate availability can directly regulate fat oxidation by coordinating hyperinsulinemia to inhibit long-chain fatty acid transport into mitochondria [4].
Carbohydrate's effect on fat oxidation during moderate-intensity exercise depends on conditioning level Civitarese's team found glucose ingestion during exercise to blunt lipolysis via decreasing the gene expression involved in fat oxidation in untrained men [5]. Wallis' team saw suppressed fat oxidation in moderately trained men and women when glucose was ingested during exercise [6].
In contrast to the above trials on beginning and intermediate trainees, Coyle's team repeatedly showed that carb ingestion during moderate-intensity (65 - 75% VO2 max) does not reduce fat oxidation during the first 120 minutes of exercise in trained men [7.8]. Interestingly, the intensity margin proximal to where fat oxidation is highest was unaffected by carb ingestion, and remained so for the first 2 hours of exercise.
Horowitz' team examined the effect of a during-training solution of high-glycemic carbs on moderately trained men undergoing either low intensity exercise (25% VO2 max) or high-moderate intensity (68% VO2 max) [9]. Similar results to Coyle's work were seen. Subjects completed a 2-hour cycling bout, and ingested the carb solution at 30, 60, and 90 minutes in. In the low-intensity treatment, fat oxidation was not reduced below fasted-state control groups' levels until 80-90 minutes of exercise. In the 68% group, no difference in fat oxidation was seen whether subjects were fasted or fed throughout the trial.
Further supporting the evidence in favor of fed cardio in trained men, Febbraio's team investigated the effects of carb ingestion pre and during training in easily one of the best designed trials on this topic [10]. Subjects exercised for 2 hours at an intensity level of 63% VO2 max, which is now known as the point of maximal fat oxidation during exercise.
The Result? Pre and during-training carbs increased performance - and there was no difference in total fat oxidation between the fasted and fed subjects. Despite the elevated insulin levels in the carb-fueled groups, there was no difference in fat availability or fat utilization.
Summing Up The Research Findings In Part 2- At low intensities (25 - 50% VO2 max), carbs during exercise reduce fat oxidation compared to fasted trainees.
- At moderate intensities (63 - 68% VO2 max) carbs during exercise may reduce fat oxidation in untrained subjects, but do not reduce fat oxidation in trained subjects for at least the first 80-120 minutes of exercise.
- Carbohydrate during exercise spares liver glycogen, which is among the most critical factors for anticatabolism during hypocaloric and other conditions of metabolic stress. This protective hepatic effect is absent in fasted cardio.
- At the established intensity level of peak fat oxidation (~63% VO2 max), carbohydrate increases performance without any suppression of fat oxidation in trained subjects.
All references are outlined
here.
About Alan Aragon Alan earned his Bachelor and Master of Science in Nutrition with top honors and is a continuing education provider for the Commission on Dietetic Registration, National Academy of Sports Medicine, American Council on Exercise, and National Strength & Conditioning Association.
He maintains a private practice, designing programs for recreational, Olympic and professional athletes, including the Los Angeles Lakers, Los Angeles Kings, and Anaheim Mighty Ducks.
Train hard; stay strong.
Peace.
Susan
If you enjoy this article, please consider sharing it via your favorite social media, likeDigg,StumbleUpon,TwitterorKirtsy. Thanks!
Similar to Part 1, this article is highly research intensive. Hang in there and we'll pull everything together later this week!
False Hopes For Fasted Cardio:
False Hopes
The b andwagon is lead by blind horses
Many trainees pigeonhole weight training as an activity exclusively for building muscle, and cardio exclusively for burning fat. On the contrary, weight training can yield very similar results to cardio of similar intensity when 24-hour energy expenditure and macronutrient oxidation is measured [1].
The obvious advantage of weight training is the higher potential for lean mass and strength gains. In the bodybuilding context, cardio should be viewed as merely an adjunctive training mode to further energy expenditure and cross-complement the adaptations specific to weight training.
As far as cardio being absolutely necessary for cardiovascular health, well, that depends upon the overall volume and magnitude of your weight training - another topic for another time.
Chaos theory strikes again
On the surface, it seems logical to separate carbs from cardio if you want a maximal degree of fat oxidation to occur during training. But, there's the underlying mistake - focusing on stored fuel usage during training instead of focusing on optimally partitioning exogenous fuel for maximal lipolytic effect around the clock.
Put another way, it's a better objective to coincide your carb intake with your day's thermic peaks, where insulin sensitivity and lean tissue reception to carbs is highest. For some reason, this logic is not easily accepted, nor understood. As we know, human physiology doesn't always cooperate with logic or popular opinion, so let's scrutinize the science behind the claims.
Let the Research Speak
Carbohydrate ingestion during low-intensity exercise reduces fat oxidation
As far as 3 decades back, Ahlborg's team observed that carb ingestion during low-intensity exercise (25 - 45% VO2 max) reduced fat oxidation compared to fasted levels [2]. More recently, DeGlisezinski's team observed similar results in trained men at 50% VO2 max [3].
Efforts to determine the mechanism behind this phenomenon have been made. Coyle's team observed that at 50% VO2 max, carbohydrate availability can directly regulate fat oxidation by coordinating hyperinsulinemia to inhibit long-chain fatty acid transport into mitochondria [4].
Carbohydrate's effect on fat oxidation during moderate-intensity exercise depends on conditioning level
Civitarese's team found glucose ingestion during exercise to blunt lipolysis via decreasing the gene expression involved in fat oxidation in untrained men [5]. Wallis' team saw suppressed fat oxidation in moderately trained men and women when glucose was ingested during exercise [6].
In contrast to the above trials on beginning and intermediate trainees, Coyle's team repeatedly showed that carb ingestion during moderate-intensity (65 - 75% VO2 max) does not reduce fat oxidation during the first 120 minutes of exercise in trained men [7.8]. Interestingly, the intensity margin proximal to where fat oxidation is highest was unaffected by carb ingestion, and remained so for the first 2 hours of exercise.
Horowitz' team examined the effect of a during-training solution of high-glycemic carbs on moderately trained men undergoing either low intensity exercise (25% VO2 max) or high-moderate intensity (68% VO2 max) [9]. Similar results to Coyle's work were seen. Subjects completed a 2-hour cycling bout, and ingested the carb solution at 30, 60, and 90 minutes in. In the low-intensity treatment, fat oxidation was not reduced below fasted-state control groups' levels until 80-90 minutes of exercise. In the 68% group, no difference in fat oxidation was seen whether subjects were fasted or fed throughout the trial.
Further supporting the evidence in favor of fed cardio in trained men, Febbraio's team investigated the effects of carb ingestion pre and during training in easily one of the best designed trials on this topic [10]. Subjects exercised for 2 hours at an intensity level of 63% VO2 max, which is now known as the point of maximal fat oxidation during exercise.
The Result? Pre and during-training carbs increased performance - and there was no difference in total fat oxidation between the fasted and fed subjects. Despite the elevated insulin levels in the carb-fueled groups, there was no difference in fat availability or fat utilization.
Summing Up The Research Findings In Part 2
- At low intensities (25 - 50% VO2 max), carbs during exercise reduce fat oxidation compared to fasted trainees.
- At moderate intensities (63 - 68% VO2 max) carbs during exercise may reduce fat oxidation in untrained subjects, but do not reduce fat oxidation in trained subjects for at least the first 80-120 minutes of exercise.
- Carbohydrate during exercise spares liver glycogen, which is among the most critical factors for anticatabolism during hypocaloric and other conditions of metabolic stress. This protective hepatic effect is absent in fasted cardio.
- At the established intensity level of peak fat oxidation (~63% VO2 max), carbohydrate increases performance without any suppression of fat oxidation in trained subjects.
All references are outlined here.About Alan Aragon
Alan earned his Bachelor and Master of Science in Nutrition with top honors and is a continuing education provider for the Commission on Dietetic Registration, National Academy of Sports Medicine, American Council on Exercise, and National Strength & Conditioning Association.
He maintains a private practice, designing programs for recreational, Olympic and professional athletes, including the Los Angeles Lakers, Los Angeles Kings, and Anaheim Mighty Ducks.
Train hard; stay strong.
Peace.
Susan
If you enjoy this article, please consider sharing it via your favorite social media, likeDigg,StumbleUpon,TwitterorKirtsy. Thanks!