If you have CFS, carbohydrate cravings are especially common during exacerbations when energy is low. Although a psychological basis for these cravings has been proposed, evidence suggests that the source is largely biochemical, possibly related to abnormalities in neurotransmitter levels and metabolism. Consumption of simple carbohydrates may increase pain, cognitive dysfunction, and fatigue, causing a “boost and crash” cycle (in which the blood sugar level rises and then plummets quickly and dramatically). Also, carbohydrates may be best tolerated in the evening.
(Source: Chronic Fatigue Syndrome, Fibromyalgia and Other Invisible Illnesses, by Katrina Berne, Ph.D.)