In-shell pistachio nuts reduce caloric intake compared to shelled nuts.
Honselman CS, Painter JE, Kennedy-Hagan KJ, et al.
Appetite. 2011;57(2):414-417.
One-hundred-forty university students were each given a 16-ounce cup filled with pistachios, shelled or in-shell, and asked to self-select a portion. Students given the in-shell pistachios ate an average of 125 calories, while those given shelled pistachios ate 211 calories—41% more calories. The authors suggest that the in-shell pistachios slowed eating time, which may have contributed to less food intake.