&gt; <i>My personal hypothesis is that some people have intestinal bacteria that are really, really good at breaking down sugar very quickly. So when you eat high GI foods, your gut turns them into glucose very quickly releases them into your blood</i><p>Are there such bacteria? I only know about intestinal bacteria breaking down indigestable carbohydrate (also called soluble &quot;fiber&quot;) into short-chain fatty acids. Other carbs except fructose (handled by liver) should be broken down into glucose via digestive enzymes prior to colon throughout the digestive tract starting in your mouth.<p>&gt; <i>IMO that would help explain why people who are very obese get type 2 with some regularity, but how otherwise healthy adults who are simply moderately overweight can also develop it.</i><p>Well many obese also never develop T2DM either. The non-fat people who become T2 might have been on a high-carb-low-fat regimen rather than a high-carb-high-fat regimen.<p>&gt; <i>A corollary to this hypothesis is that the ability of your (personal) intestinal bacteria to break down different types of foods at different rates means that there is no such thing as a &quot;universal diet&quot;. Some people will be healthiest eating large amounts of red meat, some will be healthiest on a high-carb diet, while others may need something more fiber-rich (assuming appropriate calorie control, of course).</i><p>This seems to assume an unduly large role for intestinal bacteria in digestion. Stomach acid and digestive enzymes do the bulk of the work prior, and colon bacteria get leftovers that our bodies don&#x27;t handle &quot;natively&quot; AFAIK. Exception is some cause or other flushing stuff down the tract prematurely prior to absorption, perhaps something dangerous that stomach acid didn&#x27;t neutralize, enzyme problems, overstuffing or what not..<p>&gt; <i>Intestinal flora is something the medical community is just now beginning to research and understand. There&#x27;s something unique that happens in our intestines</i><p>I agree but people shouldn&#x27;t forget bacteria only get the leftovers and if bacteria are found to be the cause of weight or health issues, maybe one should first evaluate whether enzymes are broken or too much (improperly preprocessed) cellulose is being consumed?