Whole grains aren’t all they’re cracked up to be

WUUUT *rimshot*

A new study on whole grains demonstrates how nuanced & complicated nutritional science can be.

Substituting whole grains for refined grains in a 6-wk randomized trial favorably affects energy-balance metrics in healthy men and postmenopausal women (Karl et al., 2017)

Sounds simple enough…

Study design: adequate to address the questions being asked.  Isocaloric, weight-maintenance diets.  Biggest differences between the two diets were whole grains (0 vs. 200 g/d) and insoluble fibre (15 vs. 30 g/d).

Disclaimer: I’m not a huge fan of cereal fibre, but that’s irrelevant for the point of this post.





The food was provided and the people abided.  YAY BIOMARKERS!



Nobody in either group was supposed to lose weight, but those assigned to refined grains lost more weight and fat mass, and gained more muscle than those assigned to whole grains (NS).  All of this happened despite a metabolic rate drop in refined grains and increase in whole grains:



All of this is weird.  Even weirder that the changes seemed to favor refined grains.



As expected, the whole grains group was pooping a lot more, and with it was losing almost 3 times more calories in their stools.



This should’ve increased the alleged benefits of whole grains, except it didn’t.



Hunger, fullness, diet satisfaction, eating-behavior, and food cravings were the same in both groups.  Whatevs.

No differences in glucose and insulin dynamics either.


Refined grains: no change in energy intake (by design), no change in insulin yet fat loss and muscle gain?  That’s an exaggeration, but not by much.  And as stated before, even in an ad lib context, I don’t think insoluble fibre would do much to curb obesity otherwise Metamucil would’ve done it long ago.  Best get your fibre elsewhere.  Nutrient-dense plants, even the gristly bits of “animal fibre.”  No need to max out on the grains, whole or otherwise.  It’s not even about the gluten.

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  • TechnoTriticale

    Two other press stories on this paper ignored which group lost the actual weight (vs. the calorie rate). This is why summaries of pay-walled papers are inherently suspect.

    This trial might be another black swan for the “healthy whole grains” meme, but the spinners seem to be beavering away on defending HWG.

    A no-grains arm would have been nice, but there’s probably no chance that General Mills would have funded that.


    I had a completely different understanding of “rim shot” until today.

  • BullB Man

    Hi Dr. this may not be the best place to ask this. But in a recent presentation, Dr. Stephen Phinney (https://www.youtube.com/watch?v=Qk0U006YZ2w) has mentioned about the effect of ketongenic diet on gut flora (at around 35:25 in the vid), specifically that the ?-Hydroxybutyrate could serve the purpose and provide benefits in place of the butyrate generated by the colon flora fermentation process. What’s your take on this? Is this some type of oversimplification?

    • 1) it’s wild speculation! 🙂

      2) Signaling-wise, the two molecules may have some overlapping qualities, but no idea how much quantitatively.

      3) throwing out the baby with the bathwater? Many good reasons to eat a variety of LC plants. Not just butyrate.

      • BullB Man

        Thank you for the reply Dr. Other interesting suggestions could also be found in the q&as in the vids. Agreed with the various benefits that LC plants could bring. However, this assumption (or perhaps with studies behind it that I haven’t found yet) could cause a shake to the gut flora fields, seemingly.

      • TechnoTriticale

        My gut feeling is that anyone doing KD still needs to maintain the microbiome – continue intake of prebiotic fiber/resistant starch/soluble fiber, even if in supplement form to avoid stray net carbs.

      • Emmie

        Don’t want to change the subject, but I’m interested in your take on this, Bill. I have been eating very low carb for over a decade, and recently switched to ‘zero’ (only fish, meat, fats). I seem to thrive on this (get regular labs because of thyroid), so what am I missing in no plant eating?

        Amber O’Hearn’s experience is what convinced me to try this, and her research indicates that plant foods are not essential.

        Your view?

  • MichaelGWS

    Refined grains ate 127 grams of protein, whole grains ate 115 grams of protein. #ProteinIsWinning

  • Theobroma

    Went to the link and nowhere does it say, did they use “whole grain” FLOUR or actual WHOLE grains, cooked in their genuine form? If they used the flour, whole grain flour and white flour have almost identical GI. No doubt, that would have no effect upon the insulin.

    • whole, not flour

      • Theobroma

        That is crazy o.0w

      • Theobroma

        Ooops, posted before I finished.
        I meant to say, that is crazy, but still kinda makes sense. Food is not just the sum of nutrients, it also has a unique influence upon the metabolism as a whole. When people want their animals to get fat, they do not feed them protein, they feed them grains… it’s because grains do cause gain in body mass.
        Still I’d expect white flour to give worse effects so it’s kinda surprising…

  • Jord

    I’ll stick with the scientific evidence on this, whole grain consumption has benefits in reducing risk of all cause mortality, diabetes, and other health problems.