Assuming that our current knowledge is at least partially correct, "Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process."
Directly from Wikipedia.com,
"Inflammation can be classified as either acute or chronic. Acute inflammation is the initial response of the body to harmful stimuli and is achieved by the increased movement of plasma and leukocytes (especially granulocytes ) from the blood into the injured tissues. A cascade of biochemical events propagates and matures the inflammatory response, involving the local vascular system, the immune system, and various cells within the injured tissue. Prolonged inflammation, known as chronic inflammation, leads to a progressive shift in the type of cells present at the site of inflammation and is characterized by simultaneous destruction and healing of the tissue from the inflammatory process."
So, what we may have here is another example of formerly adaptive biological processes (acute inflammation due to illness/injury) becoming maladaptive due to a novel environment ( chronic stress, impaired sleep, malnutrition, etc.)
I would say, however, that no one "needs" junk food any more than someone "needs" cocaine, alcohol, etc.
Craving carbohydrates may have been adaptive in the past, when all we would have had access to was roots, shoots, and fruits, but this also assumed that we either "fought" or "flew".
Getting yelled at by your boss, you kids having a melt-down and the grocery store, sitting in a traffic jam, etc. creates the same chemical cascade with none of the physical release of activity.
Stopping at McDonald's for a McFlurry may be the modern equivalent of pounding wild berries after outrunning a mountain lion, but we also have the capacity to use our intellect to override our instincts (at least some of the time).