The Dawn Phenomenon explains how in the morning, the liver is better at clearing insulin from the blood stream. Since you need insulin to get glucose into your cells for fuel, having no insulin is not a good thing when there is glucose in the blood stream. Here is the dawn phenomenon pathway:
Morning breakfast full of carbohydrates --> carbohydrates are converted into glucose --> need insulin to take this glucose out of the blood stream and feed it to cells --> but insulin levels are reduced as the liver tends to recycle insulin in the morning
The dawn phenomenon is especially important for diabetics. They likely will need to adjust their insulin intake in the morning to accommodate their hyper livers, eating up all the insulin that they need to process their breakfast carbs!
As for non-diabetics, the dawn phenomenon may explain the yucky some people get in the morning if they eat too many carbohydrates (and I'm not talking about Chocolate Cocoa Puffs because they make lots of people not feel their best in the morning, but something as subtle as too many slices of toast). Similarly, the dawn phenomenon may support the idea that pairing carbohydrates with protein and fat is good in the morning because they slow down carbohydrate absorption, which also means that they slow down the need for insulin, giving the liver time to snap out of it and leave insulin alone!