Diabetes is not a single disease, it is actually a group of metabolic diseases caused by inadequate insulin function. In some forms of diabetes, the problem is that insulin is not made because the cells that produce insulin are destroyed (type 1 and type 3c diabetes). In other forms of diabetes (type 2 diabetes in particular), the problem is that cells do not respond to insulin. This is called insulin resistance. The video below gives a visual representation of insulin resistance.
Type 2 diabetes usually takes many years to develop, and it all starts with insulin resistance. Insulin resistance develops under the right set of circumstances, which include genetic factors and environmental factors (see figure below). While we cannot impact genetic factors, Environmental factors are a focus of diabetes prevention and treatment. The environmental factors place strain on the cells, and damage is done SLOWLY.
To overcome insulin resistance, the beta cells of the pancreas must work harder to make more insulin. Early on in the disease process, the beta cells will get multiply in order to keep up with the demand (beta cell hyperplasia). However, over time this strain eventually results in some of the beta cells failing to work properly. We call this early beta cell failure, because enough of the cells are functioning to keep the metabolism functioning mostly normal. During this phase, blood glucose levels are seen to be modestly higher than normal, which is called prediabetes. As more time passes, more of the beta cells lose function. It is estimated that around the point where about 80% of beta cell function is lost, the person transitions from prediabetes to diabetes. It takes years of insulin resistance to cause enough beta cell damage to cause diabetes. Once someone has enough insulin resistance and beta-cell failure to develop diabetes, there is not enough insulin production to overcome resistance, and glucose levels in the bloodstream be highly abnormal.
Insulin resistance impacts organs throughout the body, disrupting normal metabolic function. Insulin resistance is associated with at least 8 metabolic defects that eventually lead to the development of diabetes, but this takes years to happen.
Because insulin resistance is the foundation of type 2 diabetes, your goal is to decrease your insulin resistance in order to prevent, manage, or cure diabetes. While most people with type 1 diabetes do not have much insulin resistance, nutrition is also key as the right diet can make insulin easier to dose and make glucose level fluctuate less.