While pistachios are a rich source of dietary fat (14g per 30g serving); almost 90% of the fat is the healthy unsaturated type, mono- and polyunsaturated. Monounsaturated fat, mostly as oleic acid, comprises 55% of the fat in pistachios. Researchers at UC Irvine recently identified an appetite-suppressing compound in oleic acid called oleoylethanolamide or OEA, which helps you feel fuller longer after a meal.