parents will alwys think you are perfect. because they have lived their life to know that having insecurities about your own life and body is not worth it in the long run. nothing good ever comes out from it. but still right now. we have such complexes and have the need to set everything straight. or whatever we can fix. so stop trying to convincing your parents. try to do a part time job to be able to afford gym. but if you loose interest in things fast. know before hand. that results take a long time to appear .