Effects of Pistachios on Postprandial Metabolic Responses in Adults With Overweight or Obesity

NCT07853898 | Recruiting

• 1 other identifier: STUDY00000569
• Study Type: interventional
• Target: 28
• Locations: 1 country
• Sites: 1

Brief Summary

This randomized controlled crossover study will examine the acute effects of pistachio consumption on postprandial metabolic responses in adults with overweight or obesity. Participants will complete two experimental conditions in randomized order. In one condition, participants will consume 30 g of pistachios with a standardized meal, and in the other condition they will receive an isocaloric refined-carbohydrate control condition with the standardized meal. The study will evaluate postprandial insulin and glucose responses over approximately 3 hours after meal consumption. Additional outcomes will include continuous glucose monitoring measures, blood lipid responses, appetite and satiety ratings, and exploratory measures related to insulin sensitivity and gastrointestinal hormone responses. The study is designed to determine whether pistachio consumption alters acute metabolic responses compared with an isocaloric refined-carbohydrate control in adults with overweight or obesity.

Conditions

Obesity / Overweight

Keywords

Pistachios; Postprandial glucose; Postprandial insulin; Metabolic response; Insulin sensitivity; Continuous glucose monitoring; Appetite

Outcome Measures

Primary Outcomes (1)

• Postprandial Insulin Incremental Area Under the Curve (iAUC)

  Postprandial plasma insulin will be measured at 0, 30, 60, 90, 120, 150, and 180 minutes after meal consumption. Insulin incremental area under the curve (iAUC) from 0 to 180 minutes will be calculated using the trapezoidal rule with baseline subtraction. Insulin iAUC will be compared between the pistachio and refined-carbohydrate control conditions.

  0-180 minutes after meal consumption

Secondary Outcomes (10)

• Postprandial Plasma Glucose Incremental Area Under the Curve (iAUC)

  0-180 minutes after meal consumption

• Continuous Glucose Monitoring Time in Range

  0-180 minutes after meal consumption

• Continuous Glucose Monitoring Mean Glucose

  0-180 minutes after meal consumption

• Continuous Glucose Monitoring Glycemic Variability

  0-180 minutes after meal consumption

• Continuous Glucose Monitoring Peak Glucose

  0-180 minutes after meal consumption

Other Outcomes (3)

• Postprandial Plasma Triglycerides

  Baseline and 180 minutes after meal consumption

• Postprandial Glucagon-Like Peptide-1 (GLP-1) Concentrations

  During the 0-180-minute postprandial period

• Postprandial Glucose-Dependent Insulinotropic Polypeptide (GIP) Concentrations

  During the 0-180-minute postprandial period

Study Arms (2)

Pistachio Then Control Sequence

EXPERIMENTAL

Participants randomized to this sequence will first complete the pistachio condition, in which 30 g of shelled pistachios are consumed with the standardized high-glycemic breakfast meal. After a 3-7 day washout period, participants will complete the refined-carbohydrate control condition, in which an isocaloric refined-carbohydrate control food is consumed with the same standardized breakfast meal.

Other: Pistachio Co-consumption; Other: Refined-Carbohydrate Control Co-consumption

Control Then Pistachio Sequence

EXPERIMENTAL

Participants randomized to this sequence will first complete the refined-carbohydrate control condition, in which an isocaloric refined-carbohydrate control food is consumed with the standardized high-glycemic breakfast meal. After a 3-7 day washout period, participants will complete the pistachio condition, in which 30 g of shelled pistachios are consumed with the same standardized breakfast meal.

Other: Pistachio Co-consumption; Other: Refined-Carbohydrate Control Co-consumption

Interventions

Pistachio Co-consumption OTHER

Participants will consume 30 g of shelled, lightly salted pistachios together with a standardized high-glycemic breakfast meal. The pistachios and standardized breakfast meal will be consumed within a fixed 10-minute meal period.

Control Then Pistachio Sequence; Pistachio Then Control Sequence

Refined-Carbohydrate Control Co-consumption OTHER

Participants will consume an isocaloric refined-carbohydrate control food together with the same standardized high-glycemic breakfast meal. The control food will be matched to the pistachio condition for energy content as closely as possible while providing minimal fiber, protein, unsaturated fat, and bioactive compounds.

Control Then Pistachio Sequence; Pistachio Then Control Sequence

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• 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.
• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• St. Louis University: lead

Study Sites (1)

Saint Louis University

St Louis, Missouri, 63104, United States

RECRUITING

MeSH Terms

Conditions

Obesity; Overweight; Insulin Resistance

Condition Hierarchy (Ancestors)

Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Hyperinsulinism; Glucose Metabolism Disorders; Metabolic Diseases

Study Officials

• Hossein Rafiei, PhD, RD

  St. Louis University

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Hossein Rafiei, PhD, RD

CONTACT

314-977-8675; hossein.rafiei@health.slu.edu

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor

Study Record Dates

• First Submitted: September 26, 2026
• First Posted: October 2, 2026
• Study Start: October 1, 2026
• Primary Completion (Estimated): July 1, 2027
• Study Completion (Estimated): July 1, 2027
• Last Updated: October 2, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)