Have they done the tests for type1or 2? You need to find out. A type 1 loses the ability to make insulin, when you get it as an adult it commonly is referred to as LADA type 1. The difference is as an adult you lose the ability over time, years even, to completely lose the ability to make insulin. A type 2 still makes insulin, they just don't utilize it right. So a type 2 usually is making extra insulin to make up for it.
A c-peptide test tells you how much insulin you are making. Low or low normal is a sign of type 1, high or high normal is a sign of type 2. Also an antibody test, which if you have antibodies it's a sign of type 1 although a few type 1's don't have antibodies but don't make insulin and they don't know why. There is also MODY and Reactive Hypoglycemia forms of diabetes.
During the honeymoon phase of a type 1, which is the period of time your ability to make insulin is stopping, your insulin production can be irregular your BG levels can vary a lot, as sometimes you make insulin and sometimes you don't. But stopping insulin if you are a type 1 can be dangerous, it can lead to DKA, which is caused by a lack of insulin in a type 1. A type 2 can get a form of DKA, but it's much rarer because they still make insulin but it still can be very dangerous. Higher BG levels show a lack of insulin or insulin being used, so you should check for ketones to know if DKA is starting.
So in answer to your question, stopping food in a type 1 means your sugars will continue to go up. Your liver continually feeds an amount of glucose to your system and if you are a type 1 you don't make the insulin to deal with it. If you are in the honeymoon phase of type 1 some people stall off needing insulin as you still make some. But it can be touchy. A type 2 is more likely to level off with less food as they still make insulin, so it's usually there, they just don't use it well. But that can vary too as once your system is out of wack, you can have varying results with BG levels.
Diagnosing Type 1 Diabetes - JDRF
https://www.diabetes.org/diabetes/complications/dka-ketoacidosis-ketones