How is type 2 diabetes a disease? Most people with type 2 diabetes are not born with it. Due to overeating, insulin is produced in higher and higher amounts to compensate for high blood sugar. Insulin pushes sugar from your blood into your cells for your body to use as fuel. Over time your body will become resistant to over production of insulin.
As insulin resistance develops, blood sugar levels will rise. This causes damage to your body by various mechanisms. Your body was not designed to constantly be flooded with sugar. Every organ in your body can be damaged and your white blood cells will no longer migrate effectively to fight infections.
People overeat for a number of reasons. High calorie foods are consumed because they taste good which makes you feel good. Overeating may also be due to stress. Type 2 diabetes is mostly due to behavior and partly to genetics. DMII is often the result of over indulging in a substance (food), that makes you feel good, or helps you cope with stress. This ultimately results in damage to your body.
How is DMII treated? Your doctor will probably tell you to work on your diet and exercise. Would they withhold life saving medication such as metformin or insulin? Would they tell you that you have weak willpower and that DMII is not a real disease? DMII is lethal when mismanaged.
How about opioid addiction? A substance is ingested (opioids) that makes people feel good or helps them initially cope with stress. Over time their body becomes tolerant to the substance. As this happens brain circuits in the reward pathway become damaged and no longer work as intended. This influences people to make poor decisions, which can lead to a lethal outcome due to overdose or misadventure.
Both DMII and addiction have a genetic and environmental/behavioral component. Neither are contagious, and generally are not born with either one. The disease processes are conceptually identical. However, how many times have you heard that addiction is not a real disease? That using medication to treat addiction is looked down upon? That weak willpower is the problem?
Both DMII and addiction have a spectrum of severity. Once brain circuitry is damaged from addiction or organs damaged from DMII, the strongest willpower in the world will not fix your body. By the time most people get help for addiction their life is in ruins and the severity of the disease is high.
We would not withhold medication to treat addiction the same way your family doctor would not withhold insulin to treat diabetes. Another perspective to consider if we take a look at the willpower argument is the following. What is more difficult to stop, heroin or a hamburger?
Every tool that exists should be used to increase your chance of surving this lethal disease.