Pathologically, digestive system diseases, diabetes, hyperthyroidism, hepatitis, nephropathy and other diseases can cause weight loss; Chronic diseases, physical weakness and malnutrition can also lead to emaciation. If you lose weight because of illness, you should treat the disease in time. When you get well, your weight will naturally return to normal. Those who are weak and malnourished after a long illness should strengthen nutrition, eat more foods rich in protein and vitamins, and properly strengthen physical exercise to restore their weight to normal.