25 body weakness no energy both physiological factors, but also disease factors, physiological factors are mostly seen in overworked work pressure, rest is not good, etc., disease factors are mostly seen in hypothyroidism, upper respiratory tract infections, anemia and so on. 1. Physiological reasons: 25-year-old young people are usually working, mostly due to work fatigue, stress, often stay up late, etc., is due to poor rest, resulting in the body does not get a good recovery will appear weak, no energy, for this situation through adequate rest, the symptoms can be significantly improved, better; 2. Causes of diseases (1) Hypothyroidism. Patients with hypothyroidism, due to the decline in basal metabolic rate, will also appear weakness and lack of energy, and severe patients will even have symptoms such as mucous edema, emotional apathy, etc. Improvement of thyroid hormone measurement can be clearly diagnosed; (2) Upper respiratory tract infections: patients with colds and flu will also show symptoms of weakness and lack of energy, limb pain. (3) anemia: this is mostly seen in young women, if the menstrual period is too much menstrual volume can easily lead to chronic anemia, will also show weakness and lack of energy and other symptoms, improve the blood routine measurement can be clearly diagnosed. Therefore, the causes of weakness and lack of energy are very complex, if it is a disease or other factors, you need to consult a doctor in a timely manner, under the guidance of the doctor systematic treatment.