This is because there is an inverse correlation between fasting plasma free fatty acids (FFA) and insulin sensitivity. Central obesity is more associated with diabetes. Intracellular triglycerides are markedly increased in muscle and liver tissues in obese individuals because the increased circulating FFA are deposited in these organs (Kumar, 1195).
It is very important for a patient suffering from diabetes to take appropriate diet and exercise to maintain normal glucose levels. In the long-term, diabetes leads to 3 main conditions, the disease of the eyes (retinopathy), nerves (neuropathy), and kidneys (nephropathy) (Kumar, 1195). These effects are due to the damaging effect of hyperglycemia on the blood vessels in these tissues. Tissues like nerves, lenses, kidneys and blood vessels do not require insulin for transport of glucose. Hence blood glucose can enter the cells without insulin. The hyperglycemia leads to increased intracellular glucose which is then metabolized by aldose reductase to sorbitol and then fructose. This process uses NADPH which gradually gets depleted resulting in oxidative stress in the cells. Thus damage to the organs occurs (Kumar, p.1195). In the retina, increased intracellular glucose stimulates the de novo synthesis of diacylglycerol from glycolytic intermediates which further causes activation of protein kinase C. Protein C causes revascularization in the retina and diabetic retinopathy, increased deposition of the extra cellular matrix, fibrinolysis and production of pro-inflammatory cytokines (Kumar, p.1195). Thus various tissues in the body are damaged as a result of blood hyperglycemia.
Studies have shown that hyperglycemia appears to be the determinant of microvascular and metabolic complications and that glycemia is much less related to the macrovascular disease.