Too Much Cardio Followup

Last Friday, I ran a short Q&A addressing the question of what defines too much cardio.  You can read that answer there, today I want to do a brief followup to one of the comments/questions from that article since it will let me address a few relevant issues.  In the comments Dan C wrote:

Isn’t to some extent, exactly what The Biggest Loser folks do? Restrictive diet in the 1k-1.5K calorie range, and then extremely high volume, low-medium intensity cardio for hours and hours? Essentially burn 2K or so cals in 4-5 hours of various stupid cardio activities and be 2K or so under Sedentary maintenance calories with their diet? Trying to make a 3.5k+ deficit every day?

Now, I’ve written a bit about the Biggest Loser previously when I ran Biggest Loser Feedback; that piece was a segue into a brutally long series on Training the Obese Beginner.  However, I didn’t really address the question that Dan asked above which is why the Biggest Loser contestants certainly don’t seem to have problems losing massive amounts of weight and fat very quickly.  This is relevant as I’ve written previously about Why Big Caloric Deficits and Lots of Activity Can Hurt Fat Loss.  So what’s going on?

Of Initial Body Fat Levels, Leptin, and Metabolic Slowdown

I’ve written previously about the impact of Initial Body Fat and Body Composition Changes; the precis on that article is that fatter individuals tend to lose more fat (and less lean body mass) while leaner individuals tend to lose less fat and more lean body mass.  However, initial body fat levels impact far more than just the proportion of fat and lean body mass lost.  And this, I believe, ties into one issue with the Biggest Loser issue.

As anybody who has read one of my books is aware, the hormone leptin is very much related to body fat levels (caloric intake also plays a role as does the type of body fat but that’s more detail than I want to cover here).  Simply, the more body fat you carry, the higher your leptin levels and vice versa.  So why is this important?

Seemingly irrelevantly, there has been a long-held argument in the research literature regarding the presence or absence of an ‘adaptive component’ to metabolic rate slowdown.  In short, when people lose weight, their metabolic rate goes down.  But sometimes it goes down more than you would predict based on the degree of fat/weight loss.  This increase in metabolic rate drop above and beyond what you’d expect is the adaptive component.

And the argument stems over the fact that while about half of the research studies find an adaptive component during weight loss, the other half does not.   Often this causes people to throw their hands up in despair and just throw science out the window but this isn’t the right approach.  Rather, you have to look at the details.

And when you look at the data set as a whole, and start to group the studies into the ones showing an adaptive component versus those that don’t a pattern starts to emerge: the studies of fatter individuals are the ones that don’t find an adaptive component while the ones in leaner (relatively speaking) folks do.  Basically, once you’re beyond a certain level of fatness, the body doesn’t fight back as hard.

In a related vein, one of the early leptin studies was looking at the impact of leptin levels on hunger during a diet.  They dieted folks and looked at how and whether or not hunger increased.  And what they found is part of the puzzle: so long as leptin was above a certain level (about 20-25 of whatever units leptin is measured in) there was no increase in hunger.  Below that level, hunger started to increase.

And the reason that all of this appears to be happening is that the leptin system in the brain can become saturated; that is, leptin levels above a certain point send no further signal.  And that saturation point seems to be around the 20-25 whatevers level.  And when you track that against body fat level, the level of fatness that equates to that leptin level is something like 20% body fat in men and around 30% in women (my memory may be failing me here, I haven’t looked at number in a while so don’t swear me to these numbers).

Basically so long as folks are above that body fat level, a lot of the metabolic perturbations that can occur in leaner folks just aren’t much of an issue.  I think that’s part 1 of why the Biggest Loser folks get away with a lot of what they get away with: some of the contestants are starting in the 40-50% body fat ranges.  Far far above where the leptin system saturates.

In contrast, most of the folks for whom I hear of problems with lots of activity and big deficits occurring is in leaner (again, relatively) folks.  Exactly the group you’d expect there to be a bigger problem.

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The Sheer Volume of Activity

The second issue I think is playing a role in the Biggest Loser situation is the sheer volume of activity.  As Dan points out, many of the contestants are being put through literally hours of fairly high intensity (at least judging by what’s shown on the show itself) on a daily basis.  Four to five hours per day (who knows, maybe more) is not uncommon.  It’s stupid but not uncommon.

And I think that’s the second piece of this puzzle.  Judging by some of the data, there seems to be a limit to how much the body can adapt to even the largest and most extreme deficits.  For example, in the now classic Minnesota Semi-Starvation Study, the study which found the largest drop in metabolic rate ever measured, the total drop was only about 40% (of which 25% was due to weight loss and the other 15% was the adaptive component).  Certainly this is large.

However, it can still be overwhelmed by a sheer metric ton of activity such that even the metabolic problems caused by the combination of large deficits and high amounts of activity can be overcome.  However, again we’re working at the extremes.  Usually the folks reporting problems with the combination of lots of activity and big deficits are doing a couple of hours of hard exercise per day (or a lot of low intensity stuff).  That’s in addition to starting out leaner.

But that’s far different than the situation in the Biggest Loser contestants where, come hell or high water, they are doing hours and hours of pretty hard training every day without fail.  In this vein, some studies of military folks, often combining sleep deprivation, hours of forced activity, and pretty hard caloric restriction find that body fat levels drop rapidly to the lower limits of survival.  But again this is a situation far removed from the average exerciser doing a couple of hours activity per day.

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The Exception that Proves the Rule?

Although this is somewhat unrelated to the two points above, I think it’s still interesting.  Clearly the Biggest Loser contestants are ‘getting away’ with something that would seem to be, on paper at least, bad.  Or at least in other less extreme populations (leaner folks doing far less activity) that causes problems.  But does that mean that the BL contestants are still doing things optimally?  That is, would a less extreme approach lead to even better results?

In the history of the Biggest Loser show, I can think of at least one or two situations where one of the contestants, usually for medical reasons, was limited to either very small amounts or very low intensity activities.  I’m thinking of one specific situation, might have been Biggest Loser Australia, where an older gentleman was put on medical restrictions.  It was either a cardiac issue or maybe an embolism.

And while everyone else on the show was just getting punished with these hours and hours of high-intensity activity and huge caloric restriction, he was limited to pretty low intensity stuff.  He also had one of the largest weight/fat losses on the show that year.  Might have won it all, I don’t recall.

In other situations, the folks who got sent home early, and who invariably did far less activity and/or used far less extreme deficits came back at the end of the show having far outstripped the contestants who were subjected to the abject stupidity of Bob and Jillian.  Those home-trained folks, the ones combining sane amounts of activity with larger caloric intakes got better results than the folks getting hammered at the extremes.

Does this prove anything?  Of course not.  But there just might be a lesson in there.

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Summing Up

And I think those are the issues worth considering.  In extremely overfat folks doing just massive amounts of activity, not only do you have a situation where the metabolic perturbations aren’t as big of an issue (at least not until a certain degree of body fat loss has occurred) but you also have a situation where the sheer amount of activity can overcome any metabolic slowdown that does occur.

Contrast that to folks starting out leaner who aren’t doing 4-5 hours of hard exercise per day but rather 1-2 and trying to combine that with a big deficit.  Not only are their bodies more likely to undergo metabolic adaptation, the volume of activity just isn’t there to overcome it.  So things grind to a crawl.

Finally is the issue that even on the Biggest Loser itself, some of the more amazing transformation came from contestants who, for whatever reason (medical or being booted off the show and training at home) got better results than the folks still on the show who were being slammed with extreme amounts of activity and big caloric deficits.

Thanks for the comment Dan, you saved me having to think a feature article topic today.

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