Hey CICO, I’m playing by your rules.

Brief background: the notorious Ebbeling study of 2012 showed an apparent metabolic advantage of a ketogenic diet.  After losing some weight, participants were assigned to low fat (LF), low GI, or ketogenic diets.  As expected, energy expenditure (EE) declined in all groups after weight loss.



However, EE declined the least in keto dieters who were burning about 300 more kcals per day than LF.  Ergo, Metabolic Advantage™.

Wrench in the gears: body composition was unaffected   O_o

If keto dieters were burning 300 more kcals per day, then surely they should have lost more fat mass.  After all, 300 kcals x 4 weeks = 8400 kcals… that should leave a mark



Kevin Hall wrote a detailed and thoughtful critique of their methodology and results, which can be summarized as: “bollixed techniques and cheating participants.”  Haha just kidding, I highly recommend reading it.

Tl;dr: there was no 300 kcal difference.


lies, damned lies and statistics


David Ludwig then wrote a detailed and thoughtful response to Hall’s critique.  You should probably read this, too.


Part 2. I think there might be a simpler way to explain at least part of the discrepancy (which I wrote about when the study was published in 2012).

The keto dieters were eating much more fat (133 vs. 47 g/d) and less fibre (11 vs. 30 g/d).  Thus, main source of fat in this study’s keto diet was more likely butter & bacon than almonds & macadamia nuts.

This. Fat absorption is very efficient in humans and fibre reduces this.

Occam’s razor?


Sherlock Holmes



Eg, the Novotny study showed that consumption of 42 grams of almonds daily reduced the digestibility of the rest of the diet by 3%, and of 84 grams by 5% (Novotny et al., 2012).  5% could account for about half of Ebbeling’s apparent Metabolic Advantage™.




And the Traoret study on peanuts vs. peanut oil showed something similar on total fecal calorie excretion (Traoret et al., 2008).


Summary: diet composition has an important, non-insignificant impact on energy balance.  So if keto and LF dieters were eating the same number of calories, but keto dieters were absorbing 300 more and also burning 300 more (or LF dieters were absorbing 300 less and also burning 300 less), then the results are exactly what we’d expect: no difference in body composition because both groups were in energy balance…

but if this is true, then keto still ramped up EE by ~300 kcals.  Is it still a Metabolic Advantage™ if you’re still technically in energy balance?

Hey CICO, I’m playing by your rules.

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  • Jack Kruse

    Bill one main variable you forgot: Mitochondrial heteroplasmy rates. Dr. Doug Wallace. Every person who reviewed this work forgot to consider this variable. %heteroplasmy controls energy balance……not the fuel that provides the electrons. https://www.youtube.com/watch?v=KwbIR2yUziw

    • The Ebbeling study was a 3-way crossover, which controls for this. A lot of variability, but overall effect was the same wrt energy expenditure: keto > LF.

    • rs711

      Hi Dr.Kruse, when you state “%heteroplasmy controls energy balance”, are you substituting ‘%heteroplasmy’ for ‘mitochondrial function’? By ‘energy balance’ are you talking about cellular Delta’G,ATP or whole body fat mass?

      Bill rightly points to the 3-way crossover design as controlling for %heteroplasmy within individuals. Furthermore, the %heteroplasmy has different phenotypic (aka clinical) effects depending on the particular thresholds of various tissues &/or individuals (a point made by Shoffner & Wallace). An example of this happens in people with dreaded MERFF (the older you are, the worse off).

      It’d be very complex (but interesting) to correlate %heteroplasmy with fat mass changes from dietary interventions. Changes from generation to generation (via mitochondrial bottlenecks) & lifestyle changes to %heteroplasmy confound this further.

  • Ela

    “This. Fat absorption is very efficient in humans and fibre reduces this.”
    Yes! This is awesome! This accords exactly with what I’ve figured out with my self-experimentation.
    Except here’s my take: why do we _want_ to reduce efficiency? For people like myself with serious neurological and gut issues (bipolar, celiac, decades-long eating disorder history), isn’t it better to reduce amount eaten (aka work for the gut) and go with efficiency?
    My nut-based ketogenic diet last summer was a disaster. But drastically reducing nuts and seeds, and overall fiber, and focusing on strict therapeutic keto ratios (mostly oils, eggs, small fish) has enabled me to get off bipolar meds, be almost completely psychosis-free, be absolutely free of bulimic tendencies, and subject to significantly less gut pain.
    I gained a lot of weight eating the nut based way with attendant bulimia (from below 90 to nearly 20lbs more), and now I seem to be maintaining at less than 1000cals/day _but without excessive hunger_. With the nuts, even keeping protein and carbs low, I would get unbearably hungry and end up binge(and-sometimes-purg)ing all too often. Inflammation/swelling issues are almost entirely gone.Gut pain which used to be my life is less frequent. My cold tolerance is the best it’s ever been, so my thyroid can’t be in the toilet(?)

    The fact that I’m so satiated on so little led me to conclude that absorption of this much fat must be very high. My extreme-anorexia history probably plays some role there too; I certainly don’t recommend it for others to do. But if I’m able to feel great and be fueled efficiently, it seems like only a good thing. Easy on my brain, easy on my guts. (I guess I do forego pretty much any social eating. But I’ve gotten my foodie kicks cheffing for others for years now. Again, it’s not going to be for everyone.)

  • Scott

    So the takeaway for weight loss is eat more nuts? Or do I have it backwards?

    • pretty much — nuts are a great source of nutrients, and studies show you spontaneously displace the calories by eating less “other stuff”