Fatigue is a natural response to over-exerting either physically, mentally or emotionally. With rest on each of these levels, the fatigue resolves and our energy is restored. But have you ever noticed that many people are tired and many are sick and tired of feeling sick and tired!
Most people push themselves every day. Especially women in their 40's, who have younger children or have spent much of their 30's rearing children and running a house-hold. Women expect to be able to hold jobs, raise kids and also stay fit, not to mention time to socialize, have time to themselves and then also have time for their partner! What ends up getting dropped from this list is the time-to-self piece. This piece is the one that typically restores energy other than sleep (if you are sleeping at all!). You can push yourself through your 20's, but once you get into your later 30's, the body wont tolerate all of the high expectations without adequate support.
When fatigue persists, despite adequate rest, it becomes chronic fatigue. There is a spectrum of chronic fatigue that ranges from that which resolves quickly with rest but may also return quickly,  to that which does not resolve despite adequate rest.
The symptom of fatigue can be due to many factors. Sometimes history alone can give me insight into what the cause of this fatigue is. When a patient comes in with fatigue, I consider the following in my approach:
Thyroid disorder
Adrenal insufficiency
Sleep problems
Inadequate nutrition
Over training
Neurotransmitter imbalance

Adequate support is key to resolving fatigue. My approach to treatment of chronic fatigue will match the severity of the fatigue. What this means is that if your fatigue is very significant and chronic, where symptoms may include muscle pain and tightness, fatigue despite rest, inability to recover from exercise, brain fog, etc, then the degree of my treatments are going to be big and may include not only supplementation with natural remedies, but may include IV therapy, hormones and significant lifestyle modification.

Fatigue is one of my favorite symptoms to help patients resolve. As a naturopathic doctor, I look at physical, emotional and mental aspects of my patients health, along with laboratory testing and then give a very comprehensive plan to restore energy.