New "Fasted Cardio"-Study Falsifies the Myth of Superior Long-Term (4 Week) Fat Loss on a Moderate Energy Deficit

If we go by the convincing results of the study at hand, the fasted cardio myth is obviously busted.

Sometimes the day you've been waiting for comes faster than you'd thought... no, I am not talking about a teen's eighteens birthday or Christmas (reminds me, I still have to buy a ton of presents), but rather of the recently hinted at "fasted cardio study" by Brad Jon Schoenfeld, Alan Albert Aragon, Colin D Wilborn, James W Krieger and Gul T Sonmez.

The study of which I wrote only 2 days ago in my article about the 50% increase in fatty acid oxidation in fasted vs. fed morning cardio (learn more). And it is in fact the study which may finally solve the "Is fasted cardio good for your weight loss?"-question.

In contrast to the previously discussed paper, Schoenfeld et al. who started with the common hypothesis that "performing aerobic exercise after an overnight fast accelerates the loss of body fat" (Schoenfeld. 2014), did not content themselves with measures of acute fatty acid oxidation. What they did was a study to investigate the actual changes in fat mass and fat-free mass following four weeks of volume-equated fasted versus fed aerobic exercise in young women adhering to a hypocaloric diet.

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Needless to say that this study has the potentially to give us reliable insights with respect to the previously formulated question, because their subjects, twenty healthy young female volunteers were randomly assigned to 1 of 2 experimental groups,

• a fasted training (FASTED) group that performed exercise after an overnight fast (n =10) or
• a post-prandial training (FED) group that consumed a meal prior to exercise (n =10)

not for one or two testing days, but for 4 weeks! The training itself consisted of 1 hour of steady-state aerobic exercise on a regular treadmill (0% incline) and was performed for 3 days per week for the previously mentioned total study duration of 4 weeks.

"Subjects performed a warm-up for the first 5 minutes at an intensity equating to 50% of maximal heart rate (MHR), determined by the formula 220 - age, then increased intensity to 70% MHR for the next 50 minutes, and finished with a 5 minute cool down at 50% MHR. Heart rate monitors (model F7U, Polar Electro Inc, Lake Success, NY) were used to ensure that exercise remained at the appropriate intensity." (Schoenfeld. 2014)

To ensure that (a) the subjects actually trained and they would (b) only do the prescribed standardized volume of exercise, all training sessions were supervised by research assistants who were upper level undergraduate students in exercise science and the subjects were instructed to refrain from performing any additional structured exercise for the duration of the study.

One thing to consider: I would not fully discard fasted cardio, yet. Even if the resulrs of the study are convincing. It's one study that simulates a specific scenario. In a real world scenario you will often have people, who do shorter fasted cardio sessions, extend the fast and thus reduce their overall energy intake. This is similar to breakfast skipping, which works magic if you don't compensate for the lack of energy intake in the AM (learn more). In the study at hand this "side effect" of morning cardio didn't exist, because of the standardization of the dietary intakes of the female participants. This is perfectly correct from a science perspective, but may still be a reason the real world results you or your clients see may differ from the null-result in the study at hand.

Subjects were provided with customized dietary plans designed to induce a caloric deficit. In that, their total caloric intake was calculated on the basis of the Mifflin-St. Jeor Equation, which yields adequate, but obviously not 100% precise measurements of the resting metabolic rate (max. 10% off in non-obese adults according to Frankenfield. 2005). Since the same method was used for both groups, any possible inaccuracies, due to which the real caloric deficit among the women may not be identical to the calculated one, should carry no real weight, though. And we can simply assume that all women were in the same ~500kcal/day energy deficit the researchers thought to create.

Figure 1: Nutrient composition and total energy intake of the subjects in both groups (Schoenfeld. 2014)

In addition to their regular diet, the adherence to which was monitored on a regular basis, the subjects received a meal replacement shake either

• immediately prior to exercise for the FED group or
• immediately following exercise for the FASTED group,

with this nutritional provision carried out under the supervision of a research assistant. The "Pursuit Recovery" (Dymatize Nutrition, TX) shake you could also buy at your local GNC contains 250 calories, total, and 40 g carbohydrate (from maltodextrin and organic cane sugar), 20 g protein (from whey protein isolate + added leucine), and 0.5 g fat (residues).

Let's  take a look at the results now

As you can see in Figure 2, both groups showed a significant loss of weight (P =0.0005) and fat mass (P =0.02) from baseline, but no significant between-group differences were noted in any outcome measure (which means, that all the differences you see are "random").

Figure 2: Pre- vs. Post-study body composition measures (Schoenfeld. 2014)

As Schoenfeld et al. rightly point out, their findings clearly "indicate that body composition changes associated with aerobic exercise in conjunction with a hypocaloric diet are similar regardless whether or not an individual is fasted prior to training" (Schoenfeld. 2014) - in other words, in this pretty realistic scenario (I hope nobody starves himself after a 1h morning cardio session for another 4-8h) the myth that morning cardio on an empty stomach would accelerate fat loss is thus busted.

Bottom line: The assumption that the consumption of an insulinogenic pre-workout meal as it was used in the study at hand and a subsequent reduction of fatty acid oxidation during the workout would induce a shift from fat to carbohydrate oxidation (not measured in the study at hand, but previous studies show that this is the case) and have significant effects on an individual's long-term fat loss on an energy reduced diet is thus falsified.

The study at hand shows that the 50% increase in fatty acid oxidation w/ fasted cardio does not translate into increased fat loss | more

You could still argue that it may be beneficial if there is no energy deficit involved, for example by improving glucose levels as it was reported by Van Proeyen et al. (2013) in a study with a hyper-caloric energy intake (~bulk), but that's a whole different story.

Or you could argue that there is an albeit non-significant trend for an increased loss of fat mass in the FASTED group (inter-group difference = 33%, but the latter was (a) paid dearly for by an almost 2x higher increase in lean mass loss (inter-group difference = 60%) and stands (b) in contrast to the non-significant greater reduction in abdominal fat in the FED group as it is signified by changes in waist circumference.

For the time being, the long-standing "myth" that fasted cardio would lead to a significant acceleration has thus to be considered "questionable", if you put 100% faith the statistical accuracy of the study at hand (with only 10 participants in both groups, I am inclined not to do that) even "busted". For so long, at least, until another study, maybe one with more participants (which would allow to really figure out how "significant" the difference actually was), but a similar strict standardization, will show that it works. In that case, we would have to find out could have been that made the difference - could be the sex or training status of the subjects, the extend of the caloric deficit, the total protein intake (which was comparatively low), the type of the pre-workout meal or the form of cardio training that was used... Comment on Facebook!

References:

• Frankenfield, David, Lori Roth-Yousey, and Charlene Compher. "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review." Journal of the American Dietetic Association 105.5 (2005): 775-789.
• Van Proeyen, Karen, et al. "Training in the fasted state improves glucose tolerance during fat-rich diet." The Journal of physiology 588.21 (2010): 4289-4302. 
• Schoenfeld, Brad, et al. "Body composition changes associated with fasted versus non-fasted aerobic exercise." Journal of the International Society of Sports Nutrition 11.54 (2014)

The Anabolic Effects of HIIT: 3x30s High Intensity Intervals Increase mTOR & Ramp Up Marker of Protein Synthesis by +43% in Men and +222% in Women - Even in a Fasted State!

Image 1: While the study at hand clearly shows that HIIT, even done on an empty stomach, is anabolic, not catabolic, it appears as if women respond better to sprint exercises than men. And this assumption is not based on gene-assays but dates back to the results of a 1999 study by Esbjörnsson which showed a more pronounced CSA increase in the leg muscles of female subjects.

Not all too long ago, the general accepted consensus was that anyone whose main interest is in building muscle must abstain from any strenuous cardiovascular exercise... running on a treadmill? God-forbid! You could lose muscle. Over the last two years or so, this paradigm has began to totter, though. And now, at the beginning of 2012 I would estimate that the number of (recognized) trainers and trainees who recommend doing high intensity interval training (HIIT), if not for general conditioning, then at least as a means to shed fat, initially surpasses the number of the conventionalists who maintain that "classic cardio" training in the "fat-burning zone" was the way to go. Now, if this is not your first visit here at the SuppVersity, you should be aware that the latest scientific research supports the arguments of the advocates of HIIT. And not so much to my, as to the surprise of some researchers, this holds true not only for already well-conditioned gymrats and athletes, who want to finally pass beyond the 10% body-fat barrier, but also for the obese and metabolically deranged diabetic, who is trying to get his blood sugar under control (cf. "Hitting Diabetes With A Hammer").

The advantages of HIIT reach well beyond fat loss, but...


Moreover, a 2011 study by Naito et al., the results of which I have discussed in November 2011, shortly after it was published in Acta Physiologica (cf. "HIT Your Satellite Cells to Increase Your Gains"), already hinted at the fact that the advantages of HIIT reach well beyond its fat-burning effects. Yet although the increase in both satellite cell count and incorporation into the muscle Naito et al. observed speak for themselves, there's still rumors going round that this training style could be catabolic. In that the argument usually revolves around the notion that muscle damage is a major driving force of satellite cell recruitement and that if the latter is a necessary consequence of HIIT it would counter your efforts to build muscle. Now, aside from the fact that this argument is intrinsically flawed (I mean, what to you do in the gym, when you weight train? You break down muscle tissue!), a recently published study from the famous Karolinska Institute in Stockholm, Sweden, attests to the fact that the exact opposite is the case.

... it appears as if women could derive even greater benefit from all-out sprinting than men

Image 2: The exercise stimulus in the study was a Wingate test, one of standard procedures in exercise science.

In an earlier study from 1999 Esbjörnsson and his / her colleagues had observed that the cross-sectional area of the leg muscles of women exhibited a more pronounced hypertrophy response to sprint training than those of their male peers (Esbjörnsson. 1999). With the advent of our advanced understanding of the underlying principles of skeletal muscle hypertrophy and the central, but as those of you who read the Hypertrophy 101 know, in the current discussion possibly overemphasized position of the mammalian target of rapamycin (mTOR), Esbjörnsson et al. did now set out to examine, whether a sex-specific response of mTOR and its downstream targets could explain their previous results (Esbjörnsson. 2012).

To this ends, the scientists recruited nine men and eight women who despite participating in leasure time sports were only "in good shape" and not considered to be athletes. For the experiment the subjects reported to the lab fasted and, after a brief 1min warm-up, performed the well-known Wingate-test, which consists of three consecutive 30s all-out sprints with 20min breaks between the intervals on a braked cycle ergometer (average peak power was ~645W and ~935W for women and men, respectively, on a per-lean body-mass base, the peak and mean power was yet identical)

Figure 1: Illustration of the experimental protocol used in the study.

Before the warm-up and 140min after the 3rd sprint, Esbjörnsson et al. took muscle biopsies from the quadriceps muscles of the subjects to assess the local expression of mTOR and its downstream targets.

Figure 2: Phosphorylated AKT, mTOR, p70S6K and rpS6 (a.u.) in male and female study participants before the first and 140min after the third sprint of the Wingate test (data adapted from Esbjörnsson. 2012)

If you are not well-versed in the the intricacies of the mTOR-cascade, it appears as if the data in figure 2 would disprove the scientists' research hypothesis that "mTOR signalling is more pronounced in women than in men". After all, the increase in phosphorylated mTOR (p-mTOR) and AKT (p-AKT) in response to the three 30s seconds sprints was obviously more pronounced in the male, than in the female participants (mTOR +26% and AKT +17% greater increases; a difference which did not reach statistical significance, though).

Do women just make better use of the same stimulus?

As far as the phosphorylation of p70S6K, of which the current scientific evidence suggests that is a more appropriate measure of the "real-world" protein synthetic effect of mTOR, a completely different picture emerges. While the +43% increase in the male subjects is just about statistically significant (p = 0.04), the +222% increase in p-p70S6K in the female subjects appears to confirm what Esbjörnsson et al. already  had suspected.

Figure 3: Serum leucine and growth hormone levels at rest and after the sprints (data adapted from Esbjörnsson. 2012)

The slightly greater disappearance of leucine from the skeletal muscle of the male subjects (cf. figure 3) is yet only one of three possible explanations (and one you could counter by ingesting BCAAs, for example) Esbjörnsson et al. come up with based on the results of previous studies:

Image 3: If you look at the leg muscles
of some of the female speed skaters,
it is quite obvious that the leg muscles
of women respond pretty well to short,
intense bouts of all-out sprinting.
(the image shows Claudia Pechstein)

1. Lower accumulation of lactate and ammonia and a faster recovery of ATP levels in type II fibers of women than men
    
2. Lower levels of plasma catecholamins (=stress hormones) in response to sprint exercises in women than in men
    
3. Slower disappearance of leucine and thusly more sustained elevation of protein synthesis in women than in men

Whether it is any of these, or a combination of all three factors which is responsible for the differential response to statistically (!) not significantly different activations of mTOR and p-AKT, cannot be decided based on the available data.

An alternative explanation, which would, by the way, have real-world implications for the training practice, is (and I prefer to cite this, to avoid being accused of sexism) that...

women do not exhaust themselves as much as men during each bout of exercise and thereby elicit a smaller activation of AMPK, resulting in less inhibition of mTOR.

In view of the fact that previous studies by Esbjörnsson et al. refute this hypothesis, it appears unlike that an "over-expression" of AMPK, of which I have discussed in one of the previous installments of the Intermittent Thoughts that its locally expressed alpha-2 isoform does not inhibit the exercise induced increase in protein synthesis, anyway, could explain why similar exercise stimuli (peak and mean power per fat-free mass were virtually identical for men and women) and within the statistical margin identical mTOR responses induce a more pronounced protein synthetic response in women than in men. And whether the early(-ier) rise in serum growth hormone, which is the last possible explanation the scientists mention, has anything to do with it appears questionably, as well. After all, the data in figure 3 shows quite clearly that the overall GH response was much more pronounced in the male than the female participants.

We don't know about aliens, but for earthlings HIIT is anabolic - regardless of their sex

In essence, it does not even really matter, what the underlying cause of the sex-specific response to sprint training is. As far as I am concerned, the most significant result of the study is not the gender-difference, but the simple, yet as the scientists point out "novel" finding that "repeated 30-s all-out bouts of sprint exercise, separated by 20 min of rest, increased Akt- mTOR signalling in skeletal muscle." And this effect was observed in both men and women. Now, this is allegedly not exactly your "usual" HIIT protocol, if you do yet take into consideration that it was performed after an overnight fast and went without BCAAs, protein shakes all the other "obligatory" anti-catabolics, the average gymrat uses to avoid the purported catabolic effects of high intensity conditioning work, I would dare to say that it HIITs another (if not a final) nail into the lid of the casket of the "HIIT = catabolic" myth.

Non-Fasted Cardio the True Key To Weight Loss? Study Shows Significant Increase in Total Energy Expenditure W/ Fed vs. Fasted Cardio - High Protein Adds to the Effect

Cardio & weight training are not mutually exclusive | learn more!

It's actually quite funny. A few days ago I wrote in a short blurb for the daily SuppVersity Classic Article that the "never-ending debate" about fasted cardio "has lost some of its momentum when the HIIT craze hit the fitness community" and today I get the following message from Päivi (thx!):

"This study totally contradicts my experience of fasted cardio. I've noticed that the best way for me to shred fat is to do fasted interval cardio, not fed one" (SuppVersity reader Päivi. March 24, 2014 | via Facebook).

"This study", in this case, refers to a soon-to-published paper from the University of Arkansas Päivi read about in a press release.

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Fasted Cardio & Beyond

In the corresponding experiment the researchers from the Human Performance Laboratory tested the differential effects of (A) fasted cardio, (B) cardio after the ingestion of a high (45%) protein meal, and (C) cardio after the ingestion of a low (15%) protein meal on the total energy expenditure of ten active (defined as burning between 500 kcal/wk and 2000 kcal/wk) women with normal body weight. And what they found is ... well, when you think about it, it's less amazing than it may appear.

Figure 1: Average metabolic rate (ml/kg/min) after the ingestion of high protein, low protein or no meal (fasted) and 40 min of cardio (5 min warm up, 30 min @60% VO2max, 5min cool down) in physically active young women (Binns. 2014)

If you take a closer look at the data in Figure 1 (and discard my analysis to the right), it may at first in fact look as if it was idiotic to do fasted cardio, if you could expend more energy if you had

• 120g of delicious oatmeal, 20oz 2% milk and a slice of wheat bread with 9g of reduced-fat peanut  butter (low protein meal), or
• 68g protein powder, 16oz of whole milk, 225g of Greek yogurt and 18g of reduced-fat peanut
  butter (high protein meal)

before the workout and still expend more energy. Now that's right: At first this may look idiotic, but if you take into account that these yummy breakfasts had slightly more than 800kcal it's highly questionable that the ~20% increase in total energy expenditure during the (presumably) 115min window that's illustrated in Figure 1 would compensate the additional energy intake of 800kcal; after all that's >50% of the lean ladies' daily basal energy requirements - a plus that would certainly not be compensated during the rest of the day.

If you want to lose weight forget about fasted or fed cardio and follow these 9 simple rules

Let's take a parting look at a pathetic increase in energy expenditure: If we do some additional math and sum up the ~6-7ml/kg/min "extra" energy expenditure for the whole 115min period (obviously that would be inappropriate because the difference is lower in the beginning), we find that the extra energy that may have looked like the solution to your "love handle problems" when you first read the abstract amounts to only ~120kcal (de facto we are probably dealing with max. 80kcal).

This leaves the ladies in the study at hand with an extra energy intake of 680kcal or 45% of their basal energy requirements. Needless to say that this was to increase energy expenditure during and after a workout is not necessarily conducive to your weight loss goals.

References:  

• Binns, Ashley, Michelle Gray, and Ro Di Brezzo. "Thermic effect of food, exercise, and total energy expenditure in active females." Journal of Science and Medicine in Sport (2014).