Much has been written about the evils of making too much insulin.
The Keto Diet is predicated on the fact that eating carbs therefore increasing insulin production will cause weight gain.
Insulin is made by a very small number of islet cells living in the pancreas. They secrete insulin into the veins that go to the liver. The insulin prevents the liver from releasing sugar into the blood stream. Insulin helps the sugars that we ingest go to storage if we are not burning them for energy. Insulin stores the sugar in the fat, muscle and liver. Insulin is the only hormone which lowers the sugar level in the body.
The brain needs a steady supply of sugar to function. We need to store sugar so that when we are not eating, the liver can release sugar into the blood stream and give us brain food. Muscles use up the sugar they have stored when you exercise. Later the muscles replenish their stores by taking sugar out of the body.
This whole process of providing food to the body whether you are eating or not is very precisely tuned and functions well UNLESS you have diabetes.
In Type 2 Diabetes, the insulin does not work properly at the level of the cell so that the body requires a lot more insulin than normal to store the sugar. People with Type 2 Diabetes are insulin resistant. In Type 1 Diabetes, the islet cells have been destroyed and insulin is not made at all. In this case, insulin is required to be given back to the body to provide for storage of nutrients.
Prior to the 1920s, insulin was not available as a medicine. People with Type 1 Diabetes could not eat carbs at all- KETO diet. Without insulin, they burned their fat and muscles for energy and wasted away. The discovery of how to manufacture insulin and administer to them, let them live.