Peak Performance, and Extremely Low Body Fat levels

“Be kind; everyone you meet is fighting a hard battle.”


credit: Sgt. Gooch

I know, I know – this is a problem everyone would love to have to deal with, I’m sure 🙂  For the serious, weight-conscious (or weight-class) athlete, though, too-low a body fat level can become a serious detriment to performance.

Mike Young, blogging for Elite Track, recently posted on the topic of how performance can be negatively affected by extremely low body fat levels.  Now for your everyday Paleo/HIT practitioner, this phenomena is of little concern, as eating a simple, Paleo diet (to satiation) and following a sensible fitness program will naturally lead an individual to a 10-ish% (male) to 15-ish% (female) body fat level.  However, this does become an issue for trainees who, for whatever reason, decides to manipulate the body to carry extremely low fat levels.  Weight-class athletes and figure competitors/bodybuilders immediately come to mind here.  Increasingly, however, CrossFit Games competitors and other power-to-bodyweight-ratio (P2BWR) conscious athletes (especially gymnasts, track and field athletes – even team-sport athletes) will attempt to squeeze-out just a little higher P2BWR by stripping off a few additional pounds of fat.  More often than not, however, this attempt backfires.  Not that the stripping away of additional fat stores is all that complicated (more on this in an upcoming post), but that at a certain point, performance (more precisely, force output and endurance) will absolutely plummet.  Quoting, now, from Mike’s post:

“…I’ve noticed that people tend to perform better at slightly higher body fat percentages. Not “big” or “fat” by any means but slightly higher than rock bottom, paper thin-skin body fat values. In fact, other than some rare cases, most athletes don’t seem to perform their best when at their lowest body fat percentages. This seems to be especially true for activities placing a premium on strength or low end power. To throw out some observational estimated figures, I’d say that 7-10% body fat appears to be the sweet spot for performance and better for performance than 4-6% body fat (the lower limits of what is physiologically possible)…”

Now why this should be so leads to some rather interesting conjectures.  Of course, unless we can attached a realistic “fix” to the “why(s)”, we’ve done little to help the athlete.  Again, quoting Mike here:

“…Is this because peak performances usually occur during times when training volumes are lower…which when combined with unmodified caloric intake lends itself to increased body fat values? Or could it be that slightly higher body fat percentages facilitate more efficient neural transmissions? Perhaps it’s because achieving extremely low body fat percentages requires what is essentially a slight starvation that in turn affects performance. I’m not exactly sure but I’ve seen this phenomenon enough times in athletes I’ve worked with to question the usual paradigm that athletes should strive for the lowest possible body fat percentages…” (emphasis mine).

Viewing this through an evolutionary prospective seems to raise as many questions as does it provide possible answers.  I agree with Mike on his observed 7 – 10% “sweet spot’ for peak performance, and if we combine this with my conjecture that following a strict Paleo diet (and eating to satiation) will naturally lead one to a 10-ish% (male) to 15-ish% (female) bodyfat level, we could argue that an ancestral hunter would be “on his game” and at his most lethal at what would be considered a natural body fat level.   Here’s where it gets a little more interesting, though.  Let’s envision a time of ancestral scarcity, and of dwindling fat stores.  Those of you who’ve reached a low body fat percentage and who’ve done any amount of intermittent fasting (IF), can attest to the feeling of “heightened acuity” and increased urgency or energy levels, the seeming lack of need to sleep for extended periods – rather tough to describe, but if you’ve been there, you know what I mean.  Now maybe this is an evolutionary “boost before the decline”, a kind of “hail Mary” pass – the last ditch effort.  But what if the hunt is still not successful, what then?  The body has now hedged its bets, put all the chips on the table.

I don’t have a satisfactory answer for this yet, other than the realization of this scenario’s forcing the body into scavenge mode – the robbing of its own protein (muscle) stores, the forced consumption of poor quality (low energy density) food-stuffs, and the resultant insulin-induced energy storage spike.

We do know, though, that the body rebels against a perceived too-low fat level via reduced energy expenditure (via a slowed metabolic rate).  But I also believe that the myelin sheath within the nervous system begins to degrade at extremely low fat levels, and that this also results in hampered performance – not only physically, but mentally as well.  As Mike says, though:

“…Ultimately it doesn’t matter because repeated real-world performance improvements trump scientific explanation…”

True enough, at least for the athlete/practitioner, who’d be well advised to keep this phenomena in mind when juggling weight-class issues, maximal P2BWR, and ultimate performance.  There are instances where dropping that last bit of fat to hit a lower weight-class/body weight level may actually be more of a performance detriment than an aid.  As always, be fearless but wise in your n=1 experimentation.

A Quick Administrative Note:

Barring any unforeseen contractual meltdowns, it seems as though Meesus TTP and I have finally sold our house; doing our damnedest,by the way, to keep housing prices severely depressed.  Anyway, the result of this is that the next few weeks will be rather frantic around TTP-ville (packing, moving, relocating, etc.), and will probably result in a diminished blogging rate – at least in the short term.  On a positive note, this is where the Paleo/HIT combination shines brightest, and where other diet/lifestyle/exercise “plans” meet their Waterloo.  Just as Paleo/HIT sustained me during the dark period of B’s passing, so it will during this stressful period.

In health,

18 responses to “Peak Performance, and Extremely Low Body Fat levels

    • This makes perfect sense. It’s the same argument as when a woman is planning to get pregnant, they say it is best that if she is at her normal weight, to gain 5 pounds to get pregnant to support pregnancy inducement. This would make sense that the extra needed nutrients & protein drain would allow “better performance” of the body to support pregnancy.

      Great article as usual, darlin!

  1. Keith,

    I can definitely attest to the “bet hedging” that your body does in a fasted state at low body fat levels.

    Good luck with the move. We bought a house recently and can attest to the mayhem involved!



  2. Quick anecdote: An ex-bodybuilder acquaintance of mine, now an avid Paleo/CF-er, told me that when he looked his “best” at ~5% BF, he actually felt his worst and was by far, his weakest.

    • Basically at 5% (for most people), dreams of sex turn to dreams of steak, you have to wear flip flops because your feet hurt from too little fat, you are constantly cold, head fogginess, little motivation…it’s not a fun place to be.

  3. Keith,

    Truly excellent post. In fact one of the the most intelligent and well presented posts I have ever read in the paleo “world”. Hope that your move goes well and that you enjoy your new house.

    Cheers – Mark

    • Thanks, Mark. And on the pending move: now is when I wish I’d listened to my grandfather’s advice to “never own more than you can carry across the river”.

  4. Hi Keith,

    Another vote from me for this:

    “But I also believe that the myelin sheath within the nervous system begins to degrade at extremely low fat levels, and that this also results in hampered performance – not only physically, but mentally as well.”

    Good luck with the move.



  5. Hi Ketith,

    just wanted to leat you know that one reader asked me to comment on this post and this is what I wrote –

    “he might be confusing dieting athletes with non-dieting athletes. There’s a difference between a glycogen-depleted run down athlete cutting to 5-6% bf vs someone in energy balance. Mike Young raised that possibility (i.e the energy deficit required to get than lean being the culprit, not bf% per se). I perform quite well at a low bodyfat%, but the last two weeks on my way to 5% bf were hard (I felt weaker and lost a rep here and there). Once I transitioned into maintenance, the feelings of weakness subsided and I regained strength.

    Btw, I certainly don’t agree with the notion that eating a paleo diet will automatically lead to 10% bf for men and 15% for women.”

    I’ll expand on that last part by saying that I’m basing this on tons of clients that, before they came to me, had been doing exactly what you suggested with no such results (i.e no weight loss and no decrease in bf% while eating a paleo diet ad libitum). To reach such relatively low bf% most often requires calorie counting and conscious restraint whether you like it or not.

    • I agree, and in fact I’m working on a follow-up post which will explore the need to weigh/measure (ala Zone) and tweak to induce the machinery to lose the last few pounds of fat. I believe the problem though (for most) stems from the trainee/client’s inability to assess true satiation – i.e., an inability to both eat properly (slowly, proper chewing, et al) and “listen to” the body. Insofar as weighing and measuring can help one become aligned with what one’s body is telling them, I’m all for it. And I do feel that this ought to be the ultimate goal, since rare is the individual who’ll “weigh and measure” for life. Actual nutrient absorption is of course another issue to deal with.

      It may well be that maintenance at a sub 7-ish % bf is doable for a competitive athlete, but I’ve not run across an instance where the risk/benefit ratio has required such an experiment.

      Also, my use of “ish” when referring to bf levels indicates my distrust of bf measurement to begin with, especially at lower levels. I think we’ve all been shocked when we are faced with the results of a visual and/or caliper estimation vs the weighed-in-water method. Which brings us back round to the more real-life (for athletes, anyway) assessment of “does it jiggle when you jump?” – if it does, then it’s not helping your P2BWR one iota.

  6. Keith,

    In economic terms, I think using stored fat for energy at this level is akin to “eating your seed corn”. You hypothalamus essentially defends a minimal level of stored fat…sort of like in minimum balance in a checking account.

    When this situation occurs, no bodyfat can be released for immediate burning in the mitochondria. Normally this is done via an adrenaline-mediated amplification cascade that releases free fatty acids to be burned in the mitochondria. Remember, a molecule of glucose going through the Krebs cycle will net 32-34 molecules of ATP. A fatty acid going through 1 turn of the Krebs cycle generates 96 molecules of ATP. This represents a complete “loss of the afterburners”.

    Over time I think the low bodyfat can result in myelin degradation, but I think the above explains the more immediate performance drops.

    Doug McGuff

    • Great stuff Doug. Thanks for that explanation. I wonder if the hypothalamus can be “coaxed” or “taught” over time to reduce the bf level at which this occurs (viz, Martin’s comment)? Or are we dealing with a “genetically pre-determined” issue?

      *Additional after thought* …the way the Golgi tendon can be desensitized to some degree…

    • Keith,

      I injured my shoulder (impingement) on my last move so I am not a big fan of moving. Good luck with yours! Wonderful post!! I am one of those (overly) obsessed with BF… good to have reminders…


      I get it now!! Thank you for the advanced biochem explanation!


  7. Awesome blogpost, and thought provoking.

    I think the issue is very individual though. Its tough to say “thou shall” or “thou shalt not” when individuals tend to vary so dramatically.

    For instance, through purely Paleo eating and exercise I’ve dropped to sub-10% bf and maintained it. This is using the space age bodyfat measurement tool known as a mirror…but thats what it looks like to me. And coming down that low has resulted in zero degredation of performance or energy. If anything I have more energy and feel fantastic. That being said I doubt I’ve fallen below the 7%-10% “sweet spot.”

    Also I’ve never had to count calories at all until just recently, in an effort to GAIN muscle mass. Losing fat involved just eating paleo and eating till I wasn’t hungry.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s