They will have more withheld, so yes, they'll get paid less, but let's say there's two people working the same hours with the same rate and will have the same deductions on their taxes with the only difference between their paychecks is one claimed 0 and the other claimed 1. They end up with their tax for the year at $1000. Now, the one claiming 0 will have paid more towards that and maybe overpaid. The one claiming 1 will have paid less towards and will get back less, but in the end they both paid $1,000 for the year.
Federal withholding is just an estimated payment towards your total tax for the year.