Although disease-related fatigue usually occurs in the diseased population, the percentage of almost healthy community-dwelling adults experiencing considerable pathological fatigue is estimated to be nearly 40% [
1], and is more often present in women than men [
7,
8]. This unexplained, idiopathic, and generalized or chronic fatigue syndrome (CFS), also known as myalgic encephalomyelitis (ME), typically emerges spontaneously with flu-like symptoms [
3]. It is characterized by a cluster of unspecific clinical symptoms such as cognitive dysfunction (“brain fog”), headaches, enlarged and painful lymph nodes, irritable bowels, unrefreshing sleep, sore throat, muscle/joint pain or morning stiffness, and severe unphysiologic postexertional malaise [
3,
9], which simultaneously serve as diagnostic criteria published by Centers of Disease Control and Prevention [
10].