The thinning of the arms may be caused by malnutrition, weak muscle strength, muscle atrophy and other factors. 1. Malnutrition: If there is partiality of food or unbalanced diet, it will lead to malnutrition, which will lead to abnormal development of muscle tissues in the arm area, thus inducing the thinning of the arm. 2. Weak muscle strength: in daily life, such as the patient’s physical exercise is too little, resulting in weak arm muscles, as well as weakening of the arm muscle strength, making the arm thinning situation. 3. Muscle atrophy: when the patient’s arm area nervous system function is impaired, causing muscle atrophy disease. Failure to notice in time can also lead to arm thinning. It is recommended that patients with arm thinning exclude physiological causes, timely medical treatment for a comprehensive examination, and in accordance with the doctor’s instructions on the cause of treatment, to avoid self-medication, affecting the health of the body. At the same time, we also need to pay attention to improve their own eating habits, more nutrient-rich foods.