As of 2006, food manufacturers are required to list trans fat on the nutrition label. Because oils are not used during roasting, pistachios are naturally trans fat-free.
Weight Management
Pistachios & Weight Management: Friend or Foe?

Research continues to show that nuts offer good nutritional value and cardio-supportive benefits. Because of their fiber, fat, and protein content, pistachios are also considered to be a satiating snack. All nuts, however, are not created equal. Pistachios are one of the lowest calorie, lowest fat nuts and offering more nuts per serving compared to any other snack nut.
Pistachios are also one of the only in-shell snack nuts – read about “The Pistachio Principle” to learn how the shell helps slow consumption and offers a visual cue for snackers.
Research Weighs-In
Researchers at Loma Linda University conducted nut feeding trials in which free living individuals substituted nuts for 20% of their total calories. The lead researcher, Joan Sabaté MD, PH.D., found that, despite the fact that nuts contain fat and are energy-dense foods, they did not cause an increase in body weight. These results for pistachios are consistent with studies of other nuts and body weight.
Good Source of Dietary Fiber
The U.S. Dietary Guidelines Committee recommends a dietary fiber intake of about 14 grams per 1000 calories, but consumption studies have indicated that Americans typically consume only half of the recommended amount. As a good source of fiber, pistachios can help meet this goal, providing 12% of the DV per serving.