to believe or not

Some things you believe right away and others you doubt no matter how much people try to convince you. Where do you sit on things like diet pills that work? With all those experts advice and research that these do work, do you believe them and would you use them or are you still doubting the experts. Often the problem is that the "expert opinion" cannot really be verified, and that's a huge holdup for a lot of people who rely on reviews to make decisions, but what about all the others who verge on the gullible and believe anyone and anything.