HIIT vs. Steady-State for Fat Loss: Can EPOC Really Explain the Benefits of Intense Interval Training (HIIT, SIE, HIE)?

HIIT vs. Steady-State for Fat Loss: Can EPOC Really Explain the Benefits of Intense Interval Training (HIIT, SIE, HIE)?

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HIIT has been touted to work its fat burning magic by increasing post-exercise oxygen consumption aka EPOC, a marker of the amount of fat you burn after your workouts. Eventually, however, only the total oxygen consumption and energy expenditure count and this is where the putative mechanism behind the fat loss effects of HIIT lacks scientific backup.

Higher excess postexercise oxygen consumption (EPOC) after high-intensity interval exercise (HIIT / HIE) and sprint interval exercise (SIE) has long been touted to explain the greater fat loss scientists observed in several studies which compared the fat loss effects effects classic "cardio" aka steady-state exercise (SSE) to interval training (HIIT / HIE).

To elucidate whether that's a reasonable and, more importantly, sufficient  (meaning: "Is the increased energy expenditure high enough to explain the fat loss, even if the steady state exercise consumes more energy and fat on total?") explanation for the previously mentioned advantages, researchers from the Healthy Lifestyles Research Center at the Arizona State University conducted a study to compare the EPOC response to the three most common forms of aerobic training: high intensity interval exercise (HIE), sprint interval exercise (SIE), and steady state exercise (SSE).

You can learn more about HIIT at the SuppVersity

Never Train To Burn Calories!

Tabata = 14.2kcal /min ≠ Fat Loss

30s Intervals + 2:1 Work/Rec.

Making HIIT a Hit Part I/II

Making HIIT a Hit Part II/II

Triple Your Energy Exp.

Ten recreationally active males (age 24 ± 4 y) participated in this randomized crossover study. On separate days, subjects completed a resting control trial and three exercise conditions on a cycle ergometer:

• HIE (four 4-min intervals at 95% HRpeak, separated by three min of active recovery); and 
• SIE (six 30-s Wingate sprints, separated by four min of active recovery); and 
• SSE (30 min at 80% of peak heart rate (HRpeak)). 

Oxygen consumption (VO2) was measured continuously during and for 3 h after exercise to estimate the actual amount of excess energy / fat that was consumed in the three treatment conditions.

Figure 1: Oxygen consumption and respiratory exchange ratio (higher numbers = higher carbohydrate to fat oxidation ratio) during the first three hours after exercise (Tucker. 2016).

Unsurprisingly, VO2 was initially higher than resting control for all three treatments. The increased oxygen consumption, which is a marker of fatty acid oxidation, however, didn't last long: After only 1 h, it returned to pre-exercise levels.

There's room for "cardio": Even though it is not popular, these days, it would be wrong to assume that classic steady state training is always the inferior choice. For someone who's killing it in the gym regularly, the additional HIIT training may in fact be too much of a sympathetic stimulus. The "boring" classic "cardio" training, on the other hand, is predominantly parasympathetic, which is why walking on an incline treadmill may eventually be a better complement to your 4-5 resistance training sessions per week than HIIT cycling or sprinting.

It is thus not really surprising that both, the complete 3-h EPOC and the total net EE after exercise were not extremely different and that that 3-h EPOC and total net EE after exercise were higher (p=0.01) for SIE (22.0 ± 9.3 L; 110 ± 47 kcal) compared to SSE (12.8 ± 8.5 L; 64 ± 43 kcal).

Figure 2: The total O2 consumption (and thus fat oxidation) and energy expenditure during the workout and the 3h thereafter shows that steady state exercise burns more fat and energy than any of the two HIIT regimen (Tucker. 2016).

What goes against the idea of increased fat oxidation after workouts due to HIIT (i.e. SIE or HIE), however, is the scientists observation that the "total (exercise + postexercise) net O2 consumed and net EE were greater (p=0.03) for SSE (69.5 ± 18.4 L; 348 ± 92 kcal) than for SIE (54.2 ± 12.0 L; 271 ± 60 kcal)" (Tucker. 2016), while those for for HIE were not significantly different from SSE or SIE, so that Tucker et al. rightly conclude that "EPOC after SIE and HIE is unlikely to account for the greater fat loss per unit EE associated with SIE and HIE training reported in the literature" (Tucker. 2016).

Bottom line: As Tucker et al. rightly point out, simple math shows that the increased energy expenditure and O2 consumption during the steady state trial more than compensates the significant, but small increase in energy expenditure and fat oxidation after the workout.

Figure 3: Minute-by-minute energy expenditure during a sedentary day and a day beginning with a single bout of sprint interval training (SIT). Data are mean values (Sevits. 2016).

It is important to know that this does not negate the results of previous studies that found beneficial effects of HIIT on fat loss. What the study does do, however, is to refute the hypothesis that these benefits were a result of an increase in EPOC and thus overall larger total energy expenditure. This, on the other hand, doesn't mean that any effects after the EPOC window of 3h investigated in the study could be responsible for said benefits. As Tucker et al. highlight, "another previously confirmed benefit of intense exercise is that it can increase the resting energy expenditure (REE) [... 17-24 h after exercise ...] in part due to an increase in sympathetic tone " (Tucker. 2016).

In conjunction with increases in the ease of locomotion (16, 17) and increase nonexercise activity thermogenesis (NEAT) (14), these effects could well explain the benefits of HIIT. Studies to confirm that are yet not just lacking, as Tucker et al. highlight, the whole-room calorimeter study of Sevits et al. (32) even suggests that SIE does not elevate REE at 24 h postexercise (see Figure 3). More studies to get to the bottom of the fat loss benefits of HIIT protocols appear warranted | Comment.

References:

• Sevits, Kyle J., et al. "Total daily energy expenditure is increased following a single bout of sprint interval training." Physiological reports 1.5 (2013): e00131.
• Tucker, Wesley J., Siddhartha S. Angadi, and Glenn A. Gaesser. "Excess postexercise oxygen consumption after high-intensity and sprint interval exercise, and continuous steady-state exercise." The Journal of Strength & Conditioning Research (2016).

Ramadan Fasting Studies Showing Fat, but no Muscle Loss Support Benefits of 'Lean Gains'-Style Intermittent Fasting

Ramadan Fasting Studies Showing Fat, but no Muscle Loss Support Benefits of 'Lean Gains'-Style Intermittent Fasting

fasting fat loss intermittend fasting lean gains lean mass lose fat muslim protein ramadan

Remember, Ramadan fasting is not about eating healthy or dieting, after sundown most Muslims consume at least as much energy as on a non-fasting day.

While scientists usually refer to alternate-day fasting as "intermittent fasting", the average fitness enthusiasts will think of Martin Berkhan's "lean gains" protocol, when he or she hears the words "intermittent fasting" - a protocol that involves fasting for minimally 16h and eating for maximally 8h and is thus somewhat similar to the "eat only after sundown" protocol Muslims follow during Ramadan.

Against that background, it makes sense to assume that the two dozen of peer-reviewed Ramadan fasting studies from the Middle East and the Muslim part of Asia provide an (albeit often uncontrolled) model for intermittent fasting.

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If we assume that this premise is true, a recent study from the Dr. Cipto Mangunkusumo General Hospital at the Universitas Indonesia, provides intriguing insights into the lean mass conserving effects of "intermittent fasting".

The study aimed to evaluate the effect of Ramadan fasting on body composition in healthy Indonesian medical staff. To this ends, Ari Fahrial Syam et al. (2016) recorded the body composition of healthy medical staff  members of the Dr. Cipto Mangunkusumo General Hospital before, during and after Ramadan fasting in 2013 (August to October).

Figure 1: Changes in body composition during the 28-day Ramadan fast (Syam. 2016).

In conjunction with data on the energy intake of the forty-three subjects, the data the scientists gathered appear to confirm what the proponents and followers of the "lean gains" variety of intermittent fasting say: You will lose body fat, but not muscle and that without significant reductions in energy intake.

According to 24h food recalls, the subjects didn't change their energy intake during Ramadan. The fat loss can thus not be explained by the induction of a caloric deficit.

Yes, the body composition was assessed by BIA, but ... while body impedance analysis (BIA) may not the best method to assess the %fa and % lean mas of trained athletes, but has been shown to have a high accuracy and reliability in "normal" people. Similarly, the 24-hour food recalls that were used to evaluate the subjects' dietary intake are often a bit off, but that's the case for both pre- and post-assessments, which is why it is reasonable to assume that there was indeed no significant change in total energy intake. This doesn't change, though that it's a pity that the scientists don't provide information about individual nutrients intakes. Previous studies suggest increased protein intakes during Ramadan fasting (Frost. 1987; El Ati. 1995) - a potentially highly relevant increase, obviously.

One thing Syam's study adds to the table, however, is that (a) the weight you will lose is not just body fat, it's also a lot of water and even bone (see Figure 1) and that (b) your (fat) weight will bounce back, within 4-5 weeks when you return to your usual eating habits.

Table 1: Overview of pertinent research comparing the results of the study at hand to previous studies (Syam. 2016).

As the research overview in Table 1 shows, some, but not all of the (side) effects are actual news. Hossini et al. (2013), for example, didn't observe changes in mineral or water content. The initially highlighted lack of protein / muscle loss, on the other hand, was observed in all three studies in which the exact body composition was measured. It is thus not unreasonable to assume that this is a characteristic feature of pertinent "intermittent fasting" protocols.

Fears about fat gain are likewise unwarranted | learn more

Bottom line: Don't get all excited, even if the 24h food recall were accurate and the fat loss occurred in the absence of reductions in food intake, the fat loss was statistically significant, but with less than 500g practically negligible.

The more important message of the study at hand is thus that intermittent fasting doesn't trigger a loss of muscle mass - a fear that is still prevalent, especially in male members of the fitness community | Comment!

References:

• El Ati, Jalila, C. H. I. R. A. Z. Beji, and J. A. B. E. R. Danguir. "Increased fat oxidation during Ramadan fasting in healthy women: an adaptative mechanism for body-weight maintenance." The American journal of clinical nutrition 62.2 (1995): 302-307.
• Frost, G., and S. Pirani. "Meal frequency and nutritional intake during Ramadan: a pilot study." Human nutrition. Applied nutrition 41.1 (1987): 47-50.
• Hosseini, Seyyed Reza Attarzadeh, et al. "The effect of ramadan fasting and physical activity on body composition, serum osmolarity levels and some parameters of electrolytes in females." International Journal of Endocrinology and Metabolism 11.2 (2013): 88.
• Faris Mohammed Ahmed, et al. "Impact of Ramadan Intermittent Fasting on Oxidative Stress Measured by Urinary 15-F2t-Isoprostane." Journal of Nutrition and Metabolism 2012 (2012).
• Norouzy, A., et al. "Effect of fasting In Ramadan on body composition and nutritional intake: a prospective study." Journal of Human Nutrition and Dietetics 26.s1 (2013): 97-104.
• Sadiya, Amena, et al. "Effect of Ramadan fasting on metabolic markers, body composition, and dietary intake in Emiratis of Ajman (UAE) with metabolic syndrome." Diabetes, metabolic syndrome and obesity: targets and therapy 4 (2011): 409.
• Syam, Ari Fahrial, et al. "Ramadan Fasting Decreases Body Fat but Not Protein Mass." International Journal of Endocrinology and Metabolism 14.1 (2016).

If You Want to Lose Weight and Stave it Off, You'd Better Not Drink Water Instead of Artificially Sweetened Beverages

If You Want to Lose Weight and Stave it Off, You'd Better Not Drink Water Instead of Artificially Sweetened Beverages

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Meanwhile, even many of those who are against the use of sweeteners admit that drinking diet coke is less of an obstacle to weight loss than regular coke. That it could, as the study at hand clearly indicates, even promote weight loss compared to water is controversial, though.

It is one of the die-hard rumors in the fitness industry: Artificial sweeteners will stall your weight / fat loss and have your weight jojo back up, when you stop dieting. As a SuppVersity reader you know that this claim is not supported by science. For the first part, controlled trials like the 2014 study by Sørensen et al. actually show that the exact opposite is the case, i.e. that the consumption of artificially sweetened beverages promotes, not hinders weight loss.

Skeptics, however, will say that "in a caloric deficit, and in comparison to regular beverages", which was the scenario in the Sørensen study,  "everything will work" - a valid argument, I have to admit. After all, the alleged insulinogenic effects said people ascribe to non-nutritive sweeteners would be more harmful during phases of attempted weight maintenance; phases as they've been investigated in a recent follow up to a previous study by Peters et al. (2015).

You can learn more about sweeteners at the SuppVersity

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To be more precise, Peters' study was a year-long trial designed to compare the effects of beverages sweetened with non-nutritive sweeteners (NNS) to water as part of a behavioral weight management program consisting of 12 weeks of active weight loss (results previously published in Peters et al. 2014) and 40 weeks of weight maintenance (results now published in Peters, et al. 2016).

Figure 1: Weight and waist loss during the initial 12-week weight loss phase of the study (Peters. 2014).

As previously discussed in the SuppVersity News on Facebook, the results from the 12-week weight
loss phase of this trial were in line with those of the previously cited study by Sørensen et al. (2014) - with the important difference, however, that Sørensen et al. compared non-nutritive sweeteners (NNS) to sugar-sweetened beverages, while Peters et al. found that the NNS group experienced greater weight loss during the 12 weeks of active weight loss, as well as more pronounced reductions in waist circumference, blood pressure, cholesterol, LDL, and triglycerides, even if the control group consumed plain water group (Peters. 2014 | see Figure 1 for weight and waist data).

Figure 2: Consuming NNSs decreased the hunger of the subjects during the 12-week weight loss phase (Peters. 2014).

Mechanistically, the observed benefits may be explained by the opposing effects the consumption of NNS sweetened beverages and water had on the subjects' appetite: Unlike the group that kept consuming artificially sweetened beverages and experienced a significant reduction in hunger scores even while dieting, the ones who were allowed to consume only water reported significantly increased levels of hunger on the 0-100 pts hunger scale Peters et al. used (see Figure 2).

Saccharin may be the unhealthy exception to the "inert sweetener" rule.

What about the effects on the microbiome? You may have heard it on BBC's "Trust me I am a doctor": saccharin appears to mess with the gut microbiome in some of us to a degree that affects our blood glucose levels. That's at least what the TV-crews mini-study shows; and in fact, as a SuppVersity reader you know that the grand daddy of artificial sweeteners (that is by the way no longer used in many products) appears to actually exert the negative effects some people ascribe to every form of sweetener. Speaking of other forms. The TV team was also able to show that stevia, which has been shown to affect the microbiome, as well (learn more), does not affect fasting glucose levels.

In the follow up paper, Peters et al. (2015) now report that the 158 male and female subjects in the NNS group did also have an easier time maintaining their weight loss than their 150 peers in the water only group (see Figure 3); a result of which the scientists say that it was neither due to differences in physical activity / sedentary time or caffeine intake, which were (within the usual statistical margins) identical in both groups.

Figure 3: Body weight (in kg) after 52-week (weight maintenance phase | left) and percent body weight regained during the weight maintenance phase (grey = water; black = NNS | right; Peters. 2015).

While Peters et al. (2015) rightly point out that "it is not possible from the present data to explain why the NNS group lost more weight than the water group despite receiving identical weight loss instruction and beverage interventions that both contained zero calories", they are right to conclude that their findings ...

"[...] are important as there continues to be uncertainty about the benefit of NNS for weight management based largely on observational studies showing associations between NNS consumption, obesity and weight gain." (Peters. 2015).

This is particularly true in view of the fact that the data clearly opposes the often voiced claim that NNS promote obesity by interfering with normal mechanisms of energy balance.

Sponsorship? Yes, the study was funded by the American Beverage Association, but (a) the American Beverage Association was not involved in the design, conduct, interpretation, or manuscript preparation of this study and a third-party organization was hired at the PIs’ request to audit data at both clinical sites to check for the accuracy and integrity of the data. Since the latter are furthermore not really open to intepretation, the "sponsorship argument" is a weak one when it comes to defending the initially defined weight loss myth. In addition, it must be said that it is unrealistic to assume that you could do a 1-year study with more than 300 subjects without external funding - especially, if the research question is not on the TOP-list of the government.

This claim, however, is - as far as experimental evidence is concerned - based exclusively on animal studies; studies that conflict with both, the study at hand and the few other published long-term human trials that evaluated NNS for weight loss (Blackburn. 1997; Tate. 2012):

Figure 4: Tate et al. observed that drinking diet beverages (DB) promotes weight loss over water (WA) or paying more attention (attention control | AC) to what you eat (Tate. 2012).

• In a prospective randomized trial, Blackburn et al. found that people with obesity in a weight loss program using NNS food and beverage products lost more weight and maintained a greater weight loss over 2 years compared to subjects not using NNS (Blackburn. 1997). 
• Tate et al. (2012) conducted a 6-month randomized trial in people with obesity and found greater weight loss over 6 months and a greater likelihood of achieving a 5% weight loss in participants drinking beverages with NNS compared with participants in an attention control group. There was no difference in the likelihood of achieving a 5% weight loss between participants in the water group versus the control or between the water group versus the NNS group.

And if we take a look at the totality of research, it becomes obvious that even observational data, some of which is often used to support the claim that artificial / non-nutritive sweeteners were among the driving motors of the obesity pandemic, indicate that artificially sweetened beverages and foods are valuable weight loss tools (Phelan. 2009). Among those of the subjects listed in the National Weight Control Registry who maintained a weight loss of at least 30 pounds for at least 1 year, for example, the vast majority of 78% says that artificially sweetened products has helped them tremendously to achieve and maintain their weight loss (Catenacci. 2014).

Artificial Sweetened Foods Promote, Not Hinder Fat(!) Loss. 1.2kg Body Fat in 70 Days By Eating Artificially Sweetened Products. Lower Hunger, Higher Fat Oxidation | more

So what's the verdict? Reliable experimental evidence for the alleged obesogenic effects of artificially or, more generally, non-nutritively sweetened beverages in humans does not exist. The number of studies showing that it supports short- and long-term weight loss and weight maintenance, on the other hand, is ever increasing.

This does not mean, though, that individual differences may make you more susceptible to overeat when you consume artificially sweetened beverages while dieting. For the average dieter, however, the 2014 study by Peters et al.  and its follow-up show that the opposite is the case. It is thus only logical that the majority of 78% of the successful weight maintainers in Catenacci's observational study from 2014 say "that they helped them control or reduce their total food or calorie intake" | Comment on Facebook!

References:

• Blackburn, George L., et al. "The effect of aspartame as part of a multidisciplinary weight-control program on short-and long-term control of body weight." The American journal of clinical nutrition 65.2 (1997): 409-418.
• Catenacci, Victoria A., et al. "Low/No calorie sweetened beverage consumption in the National Weight Control Registry." Obesity 22.10 (2014): 2244-2251.
• Peters, John C., et al. "The effects of water and non‐nutritive sweetened beverages on weight loss during a 12‐week weight loss treatment program." Obesity 22.6 (2014): 1415-1421.
• Phelan, Suzanne, et al. "Use of artificial sweeteners and fat-modified foods in weight loss maintainers and always-normal weight individuals." International Journal of Obesity 33.10 (2009): 1183-1190.
• Sørensen, Lone B., et al. "Sucrose compared with artificial sweeteners: a clinical intervention study of effects on energy intake, appetite, and energy expenditure after 10 wk of supplementation in overweight subjects." The American journal of clinical nutrition (2014): ajcn-081554.
• Tate, Deborah F., et al. "Replacing caloric beverages with water or diet beverages for weight loss in adults: main results of the Choose Healthy Options Consciously Everyday (CHOICE) randomized clinical trial." The American journal of clinical nutrition 95.3 (2012): 555-563.