Can you lose weight without being on a strict diet and just exercise?

I just joined a fitness center last thursday and I have a membership for a year. If i go to the gym 5 days a week and workout and do the different fitness classes they have, and not put myself on a very strict diet would i be able to lose weight at a good pace? Any advice on what i should do or what kind of diet I should go on? Im new at this whole fitness and losing weight thing. I am 19 years old if that helps! thank you!