Feel tired lately? Has a doctor said he can’t find anything wrong with you? Perhaps he sent you to a hospital, but all the advanced equipment there shows that there is nothing wrong with you． Then, consider this: you might be in a state of subhealth (亚健康)． Subhealth, also called the third state or gray state, is explained as a borderline state between health and disease． According to the investigation by the National Health Organization, over 45 percent of subhealthy people are middle-aged or elderly．The percentage is even higher among people who work in management positions as well as students around exam-week． Symptoms(征兆)include a lack of energy, depression(压抑),slow reactions, insomnia(失眠),agitation, and poor memory．Other symptoms include shortness of breath, sweating and aching in the waist and legs． The key to preventing and recovering from subhealth, according to some medical experts, is to form good living habits, alternate work and rest, exercise regularly, and take part in open air activities． As for meals, people are advised to eat less salt and sugar．They should also eat more fresh vegetables, fruits, fish because they are rich in nutritional elements…vitamins and trace elements …vitamins and trace elements…that are important to the body． Nutrition(营养)experts point out that it is not good to eat too much at one meal because it may cause unhealthy changes in the digestive tract(消化系统)．They also say that a balanced diet is very helpful in avoiding subhealth．