Fortunately, in a new book released April 1, Marion Nestle, Professor of Nutrition, Food Studies and Public Health at New York University and Malden Nesheim, Professor Emeritus of Nutrition Sciences at Cornell University, lay out the historical, scientific and political context of calories.

Their book Why Calories Count: From Science to Politics looks at where calories come from, how they are metabolized in the body and whether consuming fewer calories is really the key to weight loss.

Their main message? “I don’t count calories, and I don’t recommend counting calories,” Dr. Nestle said. “I recommend eating food. You have to pay attention to eating better and in moderation.”

Luckily with pistachios, it’s easy to snack smart and track calories. In-shell pistachios take longer to eat, making it easier to slow down and eat mindfully. For example, one preliminary research study found that people who snack on in-shell pistachios ate41 percent fewer calories than those that snacked on shelled nuts.^1-2

For easy reference, 100 calories of pistachios is about 30 kernels—a pile about the size of an iPhone or a computer mouse.

Read the book for the full calorie story. In the meantime, whether snacking or fixing up tonight’s meal, the authors offer this concluding advice: Get organized. Eat less. Eat better. Move more. Get political.

[1] Honselman, C.S., Painter, J.E., Kennedy-Hagan, K.J., Halvorson, A., Rhodes, K., Brooks, T.L., & Skwir, K. “In-shell pistachio nuts reduce caloric intake compared to shelled nuts.” Appetite. 2011, 57(2):414-417. The authors of this study hypothesized, but did not formally conclude, that one explanation for the reduced caloric consumption might be due to the fact that in-shell pistachios take longer to eat, encouraging snackers to slow down and be more conscious of what they’ve eaten. Appetite. 2011;57(2): 414-417.

²Painter, J. “The Effect of Pistachio Shells as a Visual Cue in Reducing Caloric Consumption.” Appetite. 2011, 57(2):418-420.