I think people vary, and also the psychology of weight loss has to be individualized.
For myself, I'm not a calorie counter, food weigher, or portion controller. I lose weight on Primal Blueprint because the types of foods I'm eating satisfy me and have normalized my hunger. I'm not spiking my blood sugar all the time with grain, and losing weight is almost effortless.
Other folks here say they don't lose weight unless they employ some sort of control- calorie counting or weighing their food and then inputting it into some computer program. I've even read that some people start out like me but then later as they get closer to goal they have to start calorie counting in order to keep it going.
So I really think it varies. I would try just eating PB to start with and see what happens. If you don't lose weight naturally (assuming you have some to lose) then you may have to start doing some sort of calorie counting.
High Weight: 225
Weight at start of Primal: 189
Current Weight: 174
Goal Weight: 130
Primal Start Date: 11/26/2012