Gyming but nt dieting..?

hey guys..m 21yrs old n i m trying to loose weight n gng 2 gym from past 15 days..but m nt able to control my diet.. so wil it effect adversely??? although i m trying hard to hav good control on fat n stuff lyk dat but m worried abt my body as it has nt shwn a bit improvement...plz help me ..thnk u..