Weight loss in 80-year-old people can be physiological factors, physiological weight loss is normal; but we can not rule out pathological factors caused by abnormal weight loss. 1. Physiological factors (1) Abnormal dietary structure: if the elderly have been vegetarian for a long time, or the economic conditions do not allow, resulting in insufficient intake of nutrients, it will cause weight loss. (2) Psychological factors: some of the elderly live alone, long-term loneliness and solitude, if overthinking, depressed mood, it will lead to a reduction in the amount of food, nutrient intake is insufficient, it will cause weight loss. (3) Difficulty in eating: with age, the teeth of the elderly are easy to loosen and fall off, which will have a certain impact on eating, and if eating is reduced, it is also easy to cause weight loss. 2. Pathological factors (1) Gastrointestinal diseases: such as chronic gastritis, peptic ulcer, inflammatory bowel disease, etc., which will affect the digestive function and lead to indigestion, resulting in insufficient intake of nutrients and causing weight loss in the elderly. (2) Cerebrovascular diseases: If the elderly suffer from cerebrovascular diseases, resulting in dementia and cognitive decline, it will have an impact on eating, resulting in insufficient intake of nutrients and causing weight loss. (3) Malignant tumors: Malignant tumors are not only consumptive diseases, but also affect the digestion and absorption of food in the intestinal tract, and therefore also lead to symptoms such as weight loss in the elderly. There are many other causes of weight loss in the elderly, in order to avoid delay in diagnosis and treatment, we should consult a doctor in time, and follow the doctor’s instructions for standardized treatment after a clear diagnosis.