Hi Thanks for posting on HCM You gain weight when you eat more than you work, that is, energy from food you eat is more than energy used for your daily activities.The excess energy will be stored in the form of proteins in muscles and fats in adipose tissues.You may also gain weight as a result of medical conditions like hypothyroidism, Cushing syndrome, PCOS, some medications... Your weight gain may not have been caused by appendix surgery.May be your life style after the surgery may have contributed.Most people have the habit if just staying and over eating after surgical interventions. No matter the cause, weight loss is possible.You just have to be patient as it gonna be a gradual process and will require some sacrifice.I will suggest you try the following: -Eat only when hungry -Exercise regularly -Choose low carbohydrate diet -Avoid junk foods and fast food -Avoid much fruits and beer -Avoid artificial sweeteners -Avoid stress and get good sleep -Eat less of dairy products and nuts -Review your medications -See your Doctor for a hormonal check -If the above measure do not help you, you may see the Doctor for weight loss pills.These drugs are however to be taken under supervision by your Doctor. Hope my answer will help you Best regards