hey, this may be a stupid question, but why do fat ppl get diabetes? i know they have more adipocytes, blah blah, but what's the mechanism of insulin resistance? also, if anyone wants to try their hand at why PCOS women get insulin resistance, i'd appreciate it.
Well, the exact mechanism isn't known, but an over-simplified explanation would be that obese people exercise less and eat more, suggesting that obesity causes diabetes in those who are genetically susceptible. Lack of exercising leads to type II diabetes because exercise has been shown to improve insulin sensitivity by recruiting glucose receptors to the surface of muscle cells; thus decreasing the amount of work that insulin needs to do. Chronic high levels of glucose and fatty acids, associated with an unhealthy diet and lack of exercise too, has been shown to be beta-cell toxic (ie killing off the body's insulin producing cells, making patients "insulin deficient"). One endocrine attending told me that type II diabetes is actually a spectrum of disorders, because there are a large percentage of patients with type II diabetes who are not obese (oftentimes seen in relatively thin, elderly African Americans who become insulin deficient, presumably since their pancreas burns out for whatever reason), and then there are types of type II diabetes associated with a stronger familial component with earlier onset and linked to different types of genes. Polycystic ovarian disease is thought to be associated with diabetes because ~50% of them are obese, and many of the same therapies used for diabetes (diet, exercise, and metformin) can be used to improve fertility and partially reverse the disease suggesting that the two diseases share some of the same causative pathophysiology. Anyways, there have been a lot of review papers and there is still a lot of active research into both of these subjects, so I will just refer you to these websites for a basic review on the topics. Let me know if you have any questions after reading the articles.