In-shell pistachio nuts reduce caloric intake compared to shelled nuts

It was hypothesized that consuming in-shell pistachios, compared to shelled pistachios, causes individuals to consume less. A convenience sample of students at a mid-western university (n = 140) was recruited, asking them to evaluate a variety of brands of pistachios. A survey at the end of class determined fullness and satisfaction. Subjects entering the classroom were given a 16-ounce cup and asked to self-select a portion of pistachios. Portion weight was recorded and subjects consumed pistachios at their leisure during class. At class end, pistachios remaining in the cup were weighed and total consumption by weight was determined. The caloric content of each portion was then calculated. In condition one, subjects offered in-shell pistachios consumed an average of 125 calories. In condition two, subjects offered shelled pistachios consumed an average of 211 calories; a difference of 86 calories. Subjects in condition one consumed 41% fewer calories compared to subjects in condition two (p ≤ .01). Fullness and satisfaction ratings were not significantly different (p ≥ .01). Caloric intake was influenced by the initial form of the food. The difference in calories consumed may be due to the additional time needed to shell the nuts or the extra volume perceived when consuming in-shell nuts.