Lack of energy after eating may be caused by overeating or thyroid adenoma. 1. Eating too much; if you eat too much or too fast when eating, it will make a lot of blood gather in the stomach and intestines, which will make the blood supply to other parts of the body insufficient, so there is a phenomenon of lack of energy, which can be improved by resting more, and eating less and more frequent, chewing and swallowing slowly. 2. Thyroid adenoma is a kind of common benign tumor disease, the course of the disease is relatively long, in the early stage of the onset of the disease, usually do not have any symptoms, with the delay of time, the tumor will continue to grow, so as to oppress the surrounding nerve tissues and organs, the phenomenon of body fatigue, lack of energy and other phenomena, and the neck will produce a sense of distension and pain, you can diagnose the condition through ultrasound and thyroid function tests. There may be other reasons for the lack of energy after eating, and if the symptoms persist and are difficult to alleviate, you should consult a doctor in a timely manner.