I work in a hospital that has a large amount of diabetic patients. I typically work stoke and ortho, and the pathology of both of those populations tend to be the result of poor lifestyle and nutrition. Strokes are the result of inflammatory conditions that cause atherosclerosis, clot formation, and resulting ischemic episode. More often than not, stroke patients have comorbidities associated with diabetes mellitus (DM) and metabolic syndrome (MS), namely obesity, and insulin resistance (IR). Most of our orthopedic patients are morbidly obese, and require significant orthopedic surgery to replace worn out joints. Others are amputees who have peripheral vascular disease with necrotic limbs that essentially rot away from poor vasculature. So, as you can see, I deal with a lot of folks that require nutritional intervention and diabetic pharmacology such as oral anti-diabetic meds like "Metformin" and a slew of long, medium, and short-acting insulins to regulate blood sugar. Unfortunately, my experience has shown me that conventional nutrition has failed many of these patients in their diabetes management.
So, I very respectfully asked, "Why not just reduce the need for insulin by giving them less carbs?" I continued, "If a person has IR and thus less insulin receptors, how is increasing insulin going to up-regulate the receptor sites (decreasing IR)?" She had no response. She told me she'd look it up and get back to me on that. She's a pretty astute gal, so I suspect she will get back to me on that. My take: the nutritional and medical philosophy in the treatment of DM, is akin to purposely clogging up a toilet and using a plunger to force it to flush. Why not just use less toilet paper?
Upregulation/Downregulation of Insulin Receptor Sites
Up and Down regulation of receptors sites occurs due to 2 sources of stimuli: Glucose and Insulin. Glucose, in excess, is toxic to cells. When chemoreceptors sense an increase in glucose they signal the beta cells in the pancreas to secrete insulin in an effort to return blood glucose (BG) levels to homeostasis (80-100 fasting, and ~90-130 one hour after meals). The process is self-limiting, as receptors are absorbed into the cell (endocytosis) after they bind to insulin. Glucose through a signaling cascade, is then able to enter the cell through the glucose transporter. The process can be seen below in figure 1.
|Figure 1. Insulin glucose cascade |
The insulin bathes all receptor sites (also leading to increased down-regulation). Prolonged or chronic hyperinsulinemia causes the absorption and breakdown of receptor sites in to the cell faster than they can be synthesized. This is further exacerbated by Tyrosine Kinase (TK) inhibition. This vicious cycle, accompanied by inflammation, causes IR. 
Glucose is either used in cells as energy, or STORED IN FAT (insulin also facilitates the storage of energy as fat). In addition to energy storage, fat acts as as sort of buffer to keep your blood nutrient and electrolyte levels in homeostasis. Remember, anything is poisonous in its proper dose whether it's water, oxygen, salt, or sugar. But in the case of IR patients, the buffer grows at an average of 1.5 lbs. per year. (the statistical weight gain of all Americans on a SAD diet)
Treatment of DM by Conventional Medicine Practitioners
As mentioned before, the current practice of nutritional support for DM patients is to calculate a caloric intake for a person based on BMI and age, and give them what's called a Consistent Carbohydrate Diet (CCHO). With a CCHO diet, the idea is that blood glucose should reach an expected BG spike, and then doctors manage that level with therapeutic insulin. But remember: diabetic patients ALREADY have excess insulin in their blood streams!
Despite this, conventional treatment is to push additional supplemental insulin in order to force glucose into the cell in order to normalize BG within the vasculature. Sure, the carb intake is predictable, but somehow blood sugars rarely are (shocker). Very rarely is a relatively low carb diet considered, and certainly therapeutic ketogenic diets have been limited to research, or the treatment of neurological disease. It's worth noting that bariatric patients have had success on ketogenic and LC diets, with healthy BMI outcomes and healthier lipid profiles and increased insulin sensitivity. But again, the conventional thinking of medical practitioners is "management", not "cure."
So, there's a schism and a dichotomy amongst medical professionals. But make no mistake about it, most of osteopathic medicine is firmly rested on the belief that dietary carbohydrates should be increased beyond what human evolution designed through millions of years natural selection.
[sarcasm] Which clearly has worked SOOOO well for them thus far, considering the fact that rates of cardio vascular disease, diabetes, and obesity, have risen despite a sharp decrease in smoking prevalence and continued dietary recommendations for low fat, high carb diets. [/sarcasm]