As one gets older, by in large, we all become less able to process the amount of sugar and carbs in the typical American diet. Breakfast is one of the most carb/sugar laden meals of the day. I skip or have vegetable juice anymore.
The why is that I eliminated meat, except for fish, from my diet and my A1C had risen to 6.2. I reversed it by eliminating sugars, most grains and starchy vegetables. I now only eat fish and carbs that are in non-starchy vegetables and my A1C went down to 5.0 in 30 days. My cholesterol has dropped from 225 to around 100.
I drink coffee until 11 AM and go straight to lunch. If I want breakfast I have it for dinner.