yes it is bad depending on how long you sleep each day and your age
a study conducted with over 1 million people showed that ppl who slept for over 8 hours had shorter life spans
also be warned if you sleep over 12 hours you could be a hypersomniac, but it could also be from fatiuge, malnutrition etc. as well
it depends on what you are doing when you are not asleep- if you are excercising and moving around i would say -NO.
on the other hand if you are simply eating and being a couch potato- then YES it could be unhealthy and lead to obesity and other health issues.
Normal health person should sleep around 6-8 hours and of course if you are too old, you may not get to sleep for 8 hours also.But more than 9-10 hours will be too bad fro sure
as goes for normal life style-sleeping for less than 6hrs and more than 8hrs caused shorter life span as per research.