Many different factors can contribute to extreme fatigue. One of the leading causes of chronic, extreme fatigue is a poor diet. When we fail to supply our bodies with the necessary nutrients that it needs, it can shut down and cause us to become exhausted in a means to get us to rest so that our body can repair damaged cells.
Stress is also a major cause of extreme fatigue. When we are constantly stressed, the mental tension that we feel causes the rest of our body to become tensed up and unable to relax. As our body's muscles remain tensed, enormous amounts of energy are expended which leaves us feeling constantly exhausted.
Many medical conditions can contribute to extreme fatigue. Vitamin deficiencies and conditions such as anemia often lead to extreme tiredness.