Monday, October 21, 2019

The Journal of Nutrition Describes Gut Bacteria Prevotella Abundance As "The Key To Successful Weight Loss" Following Short Study Where Subjects With No Prevotella Lost Comparable Amount Of Weight

Hype around preliminary findings, animal studies, cell culture studies, underwhelming studies, and more is the clickbait that sells papers and likes. Some of the time hype comes from journalists, sometimes from press-releases, and sometimes from the authors themselves. Today's blog post sees the hype coming from an invited oped published by the American Society of Nutrition's flagship The Journal of Nutrition.

The oped, entitled, The Key to Successful Weight Loss on a High-Fiber Diet May Be in Gut Microbiome Prevotella Abundance, was written in reference to the results of the study entitled, Prevotella Abundance Predicts Weight Loss Success in Healthy, Overweight Adults Consuming a Whole-Grain Diet Ad Libitum: A Post Hoc Analysis of a 6-Wk Randomized Controlled Trial.

The op-ed described the "key" to successful weight loss on a high-fiber diet as gut microbiomes containing an abundance of the bacterium Prevotella, and was written to amplify the - hold onto your hats now - findings from a very small, very short study that was not originally designed to test the relationship between Prevotella abundance and weight, that found a whole 3.5lb greater weight loss among the 15 study subjects with the highest Prevotella abundance vs. the lowest (but still present amount) when consuming a whole grain (WG) diet.

But wait, there's more!

Though it's confusing because of the way they reported weight loss, the same study found that particpants with microbiomes containing no Prevotella also lost weight on a WG diet. In fact, looking at the study's diagram detailing the losses between groups it sure appears as if subjects whose microbiomes contained no Prevotella (0-P) lost statistically comparable amounts of weight as those whose microbiomes contained the most Prevotella (High-P).

So to summarize, people with microbiomes containing what The Journal of Nutrition called, "the key to weight loss on a high-fibre diet" lost pretty much the same amount of weight as people with none of it on a high-fibre diet. Oh, and that key that worked as well as not having a key at all? If we make the enormous leap that it was causal, it led to a 3.48lb weight loss. Whoop whoop?

Bottom line I guess is that if you're going to describe something at the "key" to successful weight loss on a whole grain diet in the title of an op-ed in a prominent journal, and where we're talking about a 4lb weight loss, but having none of that key leads you to lose pretty much the same amount of weight, not only is that not much of a key, but it's incredibly irresponsible as it blatantly contributes to the ongoing erosion of societal scientific literacy and promotes the harmful and erroneous belief that magic exists when it comes to weight loss.

[Also, unless I'm misreading the very small amount of actual data provided, it would seem that the authors of the study also reported the difference between high Prevotella and low Prevotella groups wrong whereby the high group was found to have lost 4lbs (-1.8kg), and the low 0.5lbs (-0.22kg), but rather than report a -1.58kg (3.48lb) difference between the two, they added their losses and reported a -2.02kg (4.45lb) difference.]