Yawning and lack of energy all the time suggest that the body is fatigued and needs rest, the reasons include the following: 1. physiological reasons: if it is due to less rest, the body will be fatigued, at this time, if there is generous rest time, it can solve this problem better, some people often stay up late, work overtime, work pressure, all these will affect rest and sleep, so there will be yawning and other performance; 2. pathological Reasons: including snoring at night, snoring will lead to lack of oxygen, called snoring, serious sleep apnea, lack of oxygen after the brain does not get a good rest, the same body other organs, tissues also do not get a good rest, the day will not have the spirit. In addition, obese people or the body lacks certain hormones, such as lack of thyroxine, lack of sex hormones, lack of cortisol, patients will feel weak, can not fight during the day, especially the lack of thyroxine patients, called hypothyroidism, alone during the day may doze off, if the cause is pathological, it is recommended to go to the hospital for further examination.