Final answer:
In the absence of insulin, the body enters a starvation mode whereby it breaks down fat for energy and conserves amino acids, despite high levels of glucose in the bloodstream, which cannot be used by cells without insulin.
Step-by-step explanation:
When there is an insulin deficiency, as in the case of type 1 diabetes or unmanaged type 2 diabetes, the body cannot use glucose efficiently for energy. Without sufficient insulin, glucose cannot enter cells and remains in the bloodstream, leading to high blood sugar levels. This triggers the body to go into a postabsorptive or starvation mode, even though glucose is abundant. In the absence of insulin's action, the body starts breaking down fat stores into ketones for energy, a process called ketosis, which can lead to ketoacidosis if unchecked. Additionally, the liver begins to convert amino acids and other substrates into glucose through gluconeogenesis, leading to further depletion of body proteins and potential malnutrition despite high blood glucose levels, creating a paradoxical situation of 'starving in a sea of plenty.'