Question: What are the adverse effects of having too many lookup tables in the database?

I have to incorportate too many Enumerations, based on the applications. 

What would experts advice?

Answer: 
Initially you have to ask yourself "how many is too many?". If there is a logical relation between two tables, there has to be a FK.

If you don't need the related tables anywhere within the database, you could consider to remove them and use a CHECK constraint with an "IN" clause to enforce data validity. Though, this would cause an alteration of the table with each new value within the enumeration.

My personal advice is to keep the FKs and the tables. It's a clear solution and the database is way better to maintain if there is a describing text available for all those *numbers*.
Let me tell how awful it is to have too few lookup tables. THe orginal designers at one place I worked decided to put all lookups into one table and define what the lookups were for using a typeid. This caused almost all queries to hit this table to get the lookup descriptive value causing a performance jam. 

Further, without separate lookups, the fields that took the typeid were not constrained by the values appropriate to that field because a foreign key can only be on the the whole table not a chunk. So the filed that stored the clientid might accidentally contain the value for a user group. This caused data integrity problems and made reporting much more difficult as we had to intepret values that didn't make sense in context. There is no prize for using too few tables, in fact it is often an anti-pattern in database design. 

Create 1000 lookup tables if that is what you need.