Pistachios and post-meal metabolism in adults who are overweight or have obesity

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

In this randomized crossover trial, participants will try two meals in random order: one with 30 g of pistachios added to a standardized meal, and an isocaloric refined-carbohydrate control with the same meal. Postprandial insulin, glucose, appetite, and lipid responses will be measured over about 3 hours, with additional exploratory analyses on insulin sensitivity and gut hormones. Each participant serves as their own control, separated by a washout period. The goal is to see if pistachio consumption acutely modifies metabolic responses compared with the refined-carbohydrate control.

Why it matters

Who can join: the full rules

Inclusion Criteria:

* Age 18-35 years, male or female, and able to provide informed consent.
* BMI ≥25.0 kg/m². Waist circumference and BIA-derived body composition will also be assessed during screening and considered with BMI to help confirm that elevated BMI reflects excess adiposity rather than primarily high muscularity.
* Weight stable, defined as no intentional weight loss or body weight change \>3 kg during the previous 3 months.
* Generally healthy and not currently taking medications known to substantially affect glucose metabolism, insulin secretion, insulin sensitivity, appetite, or body weight. Stable thyroid hormone replacement for a well-controlled thyroid condition is not automatically exclusionary.
* Able to complete a 10-12-hour overnight fast and refrain from vigorous exercise and alcohol for 24 hours before each test meal visit.
* Able and willing to consume pistachios, the refined-carbohydrate control food, and the standardized breakfast meal.

Exclusion Criteria:

* Known diagnosis of type 1 or type 2 diabetes. Individuals with known prediabetes will not be excluded.
* Clinically significant cardiovascular disease, including prior myocardial infarction or stroke, uncontrolled hypertension, clinically significant arrhythmia, or another cardiovascular condition that could make participation unsafe or meaningfully affect study outcomes.
* Chronic kidney disease or another major medical condition that could make participation unsafe or meaningfully affect metabolic outcomes.
* Current participation in a weight-loss program, use of weight-loss medications, or history of bariatric surgery within the past year.
* Known allergy or intolerance to pistachios, tree nuts, peanuts/peanut butter, wheat/gluten, orange juice/citrus, or any other study-meal ingredient.
* Celiac disease, Crohn's disease, ulcerative colitis, or another clinically significant gastrointestinal or malabsorption condition that could affect digestion, nutrient absorption, or metabolic responses.
* Current ketogenic, very-low-carbohydrate, or medically prescribed diet that could meaningfully interfere with the standardized feeding protocol or metabolic outcomes.
* Participation in another clinical research trial within the past 3 months that could affect participant safety or study outcomes.
* Recent significant illness, infection, or surgery within the past 4 weeks that could affect participant safety or study outcomes.
* Current or prior clinically significant eating disorder that, in the investigator's judgment, could make participation unsafe or interfere with the feeding protocol.
* Current smoking, frequent nicotine use, or excessive alcohol use.
* Pregnancy, planned pregnancy during the study period, or lactation.
* Any condition or medication that, in the investigator's judgment, would make participation unsafe or interfere with outcome measures.

Where it's running

• Saint Louis University
  St Louis, Missouri, United States Recruiting

Study contacts

• Principal investigator: Hossein Rafiei, PhD, RD — St. Louis University
• Study coordinator: Hossein Rafiei, PhD, RD
• Email: hossein.rafiei@health.slu.edu
• Phone: 314-977-8675

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.