Fulsome originally meant 'sickening'. The idea was that there is too much of something - if food, that one had over-eaten and was too full. It came to be used in a general sense of 'over-abundant', 'offensive', with connotations of flattery. This is how it should be used in current academic English.
Fulsome is sometimes used in colloquial English as a more sophisticated or 'posher' way of saying 'full'. This is an error. Do not help it to creep into academic English.