Snacking on pistachios may combat metabolic syndrome risk without weight gain

More than half of Americans do not currently meet the daily recommendation of 5–7 ounce equivalents of nuts and seeds per week.

One possible contributor to such low intakes of tree nuts could be a fear that the calories or fat composition of tree nuts leads to weight gain.

For example, past studies suggest that up to 87% of Americans think eating nuts can lead to weight gain due to their dietary fat content despite scientists confirming that eating nuts every day, including pistachios, can be an achievable and simple strategy to stave off a range of health conditions with excess weight as a risk factor, including diabetes and heart disease.

Low tree nut intake by population groups including young adults in their 20s and 30s is especially problematic since they are at high risk for excess abdominal obesity and for developing Metabolic Syndrome (MetSx) - precursors to prediabetes and full-blown diabetes. In fact, the overall rate of MetSx has increased to 21.3% in this group of the population.

This New Year is the perfect time to close the book on harmful food myths once and for all. Included among these myths is the misconception that the fat content of pistachios – and other nuts – leads to weight gain, which may prevent some from reaching their 2024 self-care journey in a flavorful, nutritious, and satisfying way.

A recent study, published by Heidi J. Silver, PhD, RD, and colleagues from Vanderbilt University Medical Center, fed 84 Millennial-aged adults (22–36 years old) who had at least one metabolic syndrome risk factor (e.g., high blood pressure, high blood glucose, excess body fat around the waist, or abnormal blood cholesterol levels) either a snack of one ounce of mixed, unsalted tree nuts (including pistachios) or one ounce of a carbohydrate snack (like unsalted pretzels or graham crackers) twice per day for 16 weeks.

An overview of key findings from this study include:

• Without the study participants making any other changes to their diet (without restricting calorie intake) or lifestyle habits (without changing physical activity habits), researchers saw a 67% reduction in MetSx risk for females and a 42% reduction in MetSx risk for males who ate tree nuts in the study.
• Researchers found that participants eating one ounce of mixed tree nuts two times per day (including pistachios) had no change in their energy intake or body weight over the 16-week study period.
  • These findings are consistent with past research that showed eating as much as 15-20% of calories from pistachios does not lead to weight gain.^3,6
• In female participants, there was evidence that eating the mixed tree nuts led to reduced waist circumference (abdominal fat), a key risk factor for MetSx, diabetes, and heart disease.
• In male participants, there was evidence that eating the mixed tree nuts led to reduced blood insulin levels, another important risk factor. 
• Researchers also observed that the bodies of participants eating tree nuts were able to use fat for energy more efficiently compared to a carbohydrate snack, which may explain why the group eating tree nuts, like pistachios, did not increase body weight or body fat during the study period.
  • Past research also suggests that the body absorbs 5% fewer calories from eating pistachios than previously thought.⁷

We specifically designed the study to be able to investigate the independent effects of eating tree nuts on body weight by ensuring that the number of calories the participants ate during the 16-week intervention period matched the amount of calories they expended each day, which is one of the overall strengths of the study design and results."

Heidi J. Silver, PhD, RD, Vanderbilt University Medical Center

"This carefully designed and well-controlled study shows that eating tree nuts, like pistachios, does not have to lead to weight gain and can be an important part of anyone's self-health care routine in 2024," she explains.

The study authors also note that additional research on the cardiometabolic response to tree nuts is needed in other subgroups of the population.

Eating tree nuts, like pistachios, daily is an easy way to experience a flavorful, nutritious, and portable snack that can reinvigorate a person throughout the New Year.

In addition, to a healthy fat profile, pistachios grown in the U.S. are also a plant-based source of complete protein. Indeed, 1 serving of pistachios (1 ounce or 49 kernels) is an excellent source of protein, fiber, vitamin B6, thiamin, phosphorus, and copper.