A sudden increase in meal size in a 90 year old may be problematic. It may be due to physiological factors such as increased activity, but it does not exclude the possibility of diseases such as diabetes, hyperthyroidism or neurogenic hyperphagia. 1. Physiological factors: For example, if you have been more active recently, you may have increased food intake. 2. Diabetes mellitus: Its typical manifestations are three more and one less, i.e., eating more, urinating more, drinking more and losing weight. Fasting blood glucose, two hours after meal blood glucose, urine sugar, glycated hemoglobin and other tests can be combined to diagnose whether the patient has diabetes. 3. Hyperthyroidism: It is a consumptive disease, which is caused by abnormal hyperthyroidism. Due to the accelerated energy consumption, patients with hyperthyroidism will have hyperphagia, increased stool frequency, agitation, irritability and other manifestations. The diagnosis can be confirmed by combining with the thyroid function test. 4. Neurogenic polyphagia: mostly related to psychological factors. Patients do not have organic underlying diseases, but still feel hungry, so there will be an increase in eating. When an elderly person in his 90s suddenly has an increase in food intake, he should go to the hospital in time for a checkup after excluding physiological reasons. After identifying the cause of the disease, active treatment under the guidance of doctors.