&gt; Do you mean to say that 33% of quantifiably obese adults have unusually efficient gut bacteria?<p>Its not implausible that a substantial share of them do; there&#x27;s a lot of interesting hints in recent research suggesting that elements of modern lifestyles in the US may have substantially affected gut microbiomes over the last several generations, starting with very early life changes that affect the way they get initially established.<p>An important part of the obesity epidemic -- though almost certainly not its <i>sole</i> cause; diet and activity pattern changes with effects other than via the composition of the microbiome certainly exist -- may well be widespread disruption of normal gut microbiome.