Before I was diagnosed with type 2 diabetes, I practically lived on fast food. I rarely ordered a single hamburger if a double or triple were available. Of course I had to upsize in order to get a larger order of french fries, and the drink couldn't be diet. A fried pie for dessert made perfect sense.
Shortly after I got diagnosed, I did an experiment. I ate one last fast food meal and then checked my blood sugar. It was 300+. Two hours later it ramped down to around 175, which is still not ideal for a diabetic. I couldn't believe I was doing that much damage to myself every day. If I eat fast food at all, I substitute a small salad for the fries and drink water or unsweet iced tea.