In Steady State vs. Intervals: Explaining the Disconnect Part 1, I started to examine some other physiological explanations (outside of EPOC) to potentially explain the seeming disconnect between the total irrelevancy of EPOC and both the research and real-world fat loss results from interval training. I’m going to continue and conclude that discussion today by looking at some other mechanisms by which interval training may be affecting fat loss in both research and the real world.
The Hormonal Response
The hormonal response to any kind of high-intensity training is significantly different than in response to low-intensity training. While low intensity training typically only releases noradrenaline (from the nerve terminals) with only small amounts of adrenaline (from the adrenal medulla), high-intensity exercise releases both adrenaline/noradrenaline in large amounts.
For various reasons, all of which are discussed in some detail in The Stubborn Fat Solution, that hormonal response can be beneficial to fat loss. Quite in fact, in that book, I use intervals for specifically that reason in two of the stubborn fat protocols.
In addition to potentially impacting on fat mobilization (lipolysis), this hormonal response can have one other major effect that is probably a major cause of the results in many of the studies being cited by the pro-interval group. That’s that high intensity exercise often blunts hunger.
If there is a single glaring flaw in nearly all of the research that is being used either in support of intervals or to tear down steady state cardio, it’s that diet is uncontrolled. This is important for two reasons, one physiological and one practical.
The practical one should be pretty damn obvious: anybody who is trying to lose fat without paying attention to their diet has it ass-backwards (for context, one of the most rabid pro-interval gurus has ‘Correct Nutrition’ as the #1 bit of importance in his Fat-loss Heirarchy). He’s assuming that diet is fixed, and then using research that is not controlling diet at all.
The other issue is a physiological one, having to do with how exercise can impact on appetite. Now, this could be an entire blog post (or series in its own right) as there are myriad physiological and psychological ways that training can impact on appetite (sometimes exercise decreases hunger, sometimes it increases it).
However, at least one data point shows rather clearly that high intensity activity tends to blunt hunger more than low-intensity activity.
Quite in fact, in one of the studies currently being used to claim that ‘Steady state cardio makes you fatter’ (the steady state group had a 0.5 kg fat gain in visceral fat compared to a 0.5 kg fat loss in the interval group), the researchers explicitly state:
“However, our estimates of energy expenditure and intake lack sufficient precision to comfortably conclude that energy balance was unaffected in the HIIE condition. Thus, it is feasible that the change in FM that occurred in HIIE may have been influenced by unreported changes in diet. Indeed, HIIE- induced suppressed diet intake may be one of a number of possible factors underlying the fat loss effect of HIIE.11 For example, HIIE may have suppressed appetite or decreased attraction for energy-dense foods.24,25.”
Meaning that the interval group may have lost fat because the exercise may have made them eat less.
While a huge benefit if someone isn’t controlling calories has no real relevance if they are. I’d also note that the total fat loss in that specific study wasn’t much, a whopping 1.5 kg (3.3 lbs) over 15 weeks. The Rapid Fat Loss Handbook can take that much fat off of a person in ONE WEEK.
Tangential question with a tone that moves beyond snarky and to outright accusation: how come the pro-interval gurus who trot out these studies don’t ever mention these specifics when they claim that intervals are superior to steady state cardio? That the intervals may have simple worked because subjects ate less, or that the actual real-world fat loss amounted to jack shit in the first place?
Making People Work Harder for a Damn Change
Ok, this one isn’t addressed in the research but it’s still important to results.
Let’s face facts, most people train like wimps. I don’t care how hard they claim to work, I’ve spent damn near 20 years in commercial gyms and the simple fact is that most don’t.
Go look at the average person on the treadmill, odds are they aren’t even breaking a sweat or doing anything beyond watching tv and talking on their cell phone. And while my comparison on Saturday was intervals to a moderate aerobic sessions (where I can easily burn 10 cal/min), the average person may be burning closer to 5 cal/min during ‘fat-burning’ cardio. Or 150 calories over a 30 minute pissant steady state session. Under those conditions, a 20 minute interval session (which may burn 200+ calories) actually does win out from a simple energy balance perspective, in addition to any other benefits discussed above.
If there’s one thing that the whole interval training fad has done, it’s to get people to actually work somewhat out of their comfort zone. But to a great degree, this has less to do with steady state cardio as a modality and more about how it’s used. Fine, people usually do steady state cardio at irrelevant intensities. No argument here. But that has nothing to do with steady state and more to do with the fact that people are
- Being given shitty advice (fat burning zone, bro)
So, yes, if telling them that intervals is going to MELT THE FAT OFF OF THEM actually gets them to work hard, that’s a benefit. I’d also note in this context that this can backfire. People who are too wimpy to suffer aren’t going to do intervals effectively and will probably end up getting LESS out of an interval workout (that they half-ass) than a properly done steady state cardio session (which they’ll also half-ass).
And of course none of this really gets back to the question I posed on Saturday regarding how often I can or should do intervals compared to how often I can or should do steady state. Which is what my next article will discuss.
Now let’s take a quick look at the topic of Exercise Efficiency