Malnutrition causes fat and swollen legs and feet, usually low-protein edema. Prolonged malnutrition leads to protein deficiency. Protein is in negative nitrogen balance, serum total protein is less than 40g/L, albumin is less than 20g/L, plasma colloid osmotic pressure reduces water, which may seep into the tissue interstitial space, resulting in edema. For example, gastritis, enteritis and other long-term chronic gastrointestinal diseases, anorexia, etc. lead to insufficient food intake, low protein intake, causing fat and swollen legs and feet. Massive blood loss, drainage of surgical wounds, severe burns, ascites, pyothorax, lung abscess, etc. lead to a large loss of protein in the body, resulting in malnutritional edema. In addition, liver diseases, such as cirrhosis and hepatitis, lead to a serious decline in liver function, which affects protein synthesis, leading to low plasma albumin, resulting in low-protein edema, leading to fat and swollen legs and feet. Severe malnutrition, resulting in a lack of energy and protein in the body, if it lasts for a longer period of time, leading to peripheral edema or swelling of the legs and feet. It is recommended to eat a reasonable diet and, if necessary, go to the hospital for treatment under the guidance of a doctor.