The peanut butter diet is a low-calorie meal plan that allows dieters to consume four to six tablespoons of natural peanut butter each day. Peanut butter, which is rich in protein and healthy fat, keeps dieters from feeling deprived between meals. In addition to peanut butter, dieters can eat fruit, vegetables, lean protein, low fat dairy, and whole grains. For people who love peanut butter, this diet is a great way to lose weight. While peanut butter alone will not cause weight loss, it is effective when paired with a reduced calorie diet.