You are right what i said was by far in a way an oversimplified and technically incorrect. As far as classifications the current American Diabetes Association (ADA) classification of diabetes mellitus does not reflect the clinical heterogeneity of patients with diabetes and the emergence of the concept and evidence that early beta cell dysfunction is likely to be a primary defect in the pathophysiology of diabetes, regardless of "type." Furthermore, The high prevalence of overweight/obesity in the population has further complicated classification systems with an added element of insulin resistance even in type 1 diabetes. So classifying diabetes into two or three types is technically incorrect because its far more complicated than that, but for most cases does not change the treatment and management. Currently one system used subdivides type one to type A(immune mediated) or type B with total insulin deficiency and no c-peptide levels but idiopathic in nature and without immune destruction or present of antibodies. Thus, genetic markers for type 1A diabetes are present from birth, immune markers are detectable after the onset of the autoimmune process, and metabolic markers can be detected with sensitive tests once enough ß-cell damage has occurred, but before the onset of symptomatic hyperglycemia. This long latent period is a reflection of the large number of functioning beta cells that must be lost before hyperglycemia occurs. As previously stated type 2 does not involve immune mediated destruction and their gene loci involved do not appear to overlap however, inflammation ( interleukin-1 mediated) may play a role in islet beta cell loss in both types. Type 1 is more likely to occur at a young age, but its not always the case as in latent autoimmune autoimmune in adults or LADA. Maturity onset diabetes of the young (MODY) is another subtype of type1 which is a clinically heterogeneous disorder characterized by non-insulin dependent diabetes diagnosed at a young age (<25 years) with autosomal dominant transmission and lack of autoantibodies however, only accounts for approximately 2-5% of total cases of diabetes. Whereas in the US type 2 which makes up about 90% is a result of complex polygenetic risk factors and environmental effects. Genetically the genes known to influence type 2 i believe there are maybe 14 don't influence your response to insulin which would make more sense, but rather how your pancreas makes insulin in the first place. Moreover, how healthy your pancreas starts out could determine how vulnerable you are to other diabetes triggers, like getting fat and obesity. In the past, poor metabolic control of type 1 diabetes prevented most patients from gaining weight. However, Intensive therapy now commonly used to manage type 1 diabetes has resulted in approximately 20 to 30 percent of type 1 diabetic patients becoming overweight or obese. Insulin resistance and other features of type 2 diabetes may be exhibited in overweight patients with type 1 diabetes, especially those who also have a family history of type 2 diabetes. Thus, need for insulin does not distinguish between type 1 and type 2 diabetes. The presence of GAD and islet cell antibodies in patients with presumed type 2 diabetes can identify patients who actually have type 1 diabetes (LADA) and more likely to require insulin as destruction progresses. Screening for LADA criteria are age of onset <50 years, acute symptoms, BMI <25 kg/m2, and personal or family history of autoimmune disease. Obesity by far in a way is the largest external risk factor especially those body type with predominate truncal obesity. However many other diseases contribute to the development of diabetes suchs as cystic fibrosis, hereditary hemochromatosis, chronic pancreatitis, and endocrine abnormalities such as cushings disease, acromegaly, somatostatin-secreating tumors, hyperthyroidism, and glucagon-secreting tumors. The problems of diabetes are by far in a way caused by non-enzymatic glycosylation like in diabetic retinopathy or osmotic damage. This is by far in a way not even close to being complete doesn't even touch on common things such as gestational diabetes or type 3 diabetes secondary to alzheimers disease.