That's false though. You don't have to start out committed to anything. You can simply pick up a religious book or attend a religious service and see if it speaks to you.
Are you a believer? Do you think it is enough to just say "I do not believe anymore for the next 2 weeks", really meaning it? If so, it means that the faith was not very strong.
Except for some specific cases, one usually grows with a religion or non-religion and this deeply forges one's perspective.
I'm an adult convert. So what I'm telling you is, I didn't have to start out believing; just curious. Obviously atheism is different because there is no particular doctrine or liturgy to involve yourself in, but you could certainly read atheist polemic.
Except for some specific cases, one usually grows with a religion or non-religion and this deeply forges one's perspective.