Many things can cause high blood sugar, but what we eat plays the biggest and most direct role in elevating blood sugar. When we eat carbohydrates, our body converts those carbohydrates into glucose, and this can play a role in raising blood sugar. Protein, to a certain degree, in high amounts can also raise blood sugar levels. Fat does not raise blood sugar levels. Stress leading to an increase in the hormone cortisol can also raise blood sugar levels.
Learn more in Dr. Sarah Hallberg's video on how what we eat impacts our blood sugar.