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NCT Number: NCT07340125

Pistachio Snacking and Metabolic Flexibility

The purpose of this study is to evaluate the effects of pistachio snacking on metabolic flexibility (at rest, during exercise, and in post-exercise recovery) in healthy overweight and obese adults. Secondary goals include evaluating effects on changes in diet quality, sleep characteristics, physical activity, and hormonal health in women. In randomized order, participants will complete four days of pistachio snacking and four days of normal dietary habits (control). For both conditions, primary outcomes of resting substrate metabolism, metabolic flexibility during exercise, and post-exercise substrate metabolism will be measured pre-post intervention via indirect calorimetry. Secondary outcome of diet quality (kcal, carb, fat, protein) will be measured pre-post intervention via diet log. Exploratory outcomes of daily physical activity (steps, intensity), nightly sleep characteristics (quantity, quality, latency, efficiency), and daytime sleepiness and hunger.

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Key information

Conditions

Overweight (BMI > 25) Body Weight Healthy Participants Nutrition Disorders Nutritional and Metabolic Diseases Obese But Otherwise Healthy Participants Obese Patients (BMI ≥ 30 kg/m²) Obesity Overnutrition Overweight Overweight or Obese Pathological Conditions, Signs and Symptoms Physically Inactive Poor Sleep Quality Signs and Symptoms

Age range

25 year–45 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Public Health Research Center: Clinical Exercise Research Center

Columbia, South Carolina, 29208, United States

Location status: Recruiting

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Males and Females
  • Age: 25-45 years
  • Overweight or obese (BMI=25.0-34.9 kg/m²)
  • Poor sleep quality (Pittsburgh Sleep Quality Index ≥ 5)
  • Healthy (no diagnosed metabolic, cardiovascular, sleep, or other health condition that may significantly alter metabolism, sleep, or ability to participate in the exercise test)
  • Not meeting weekly physical activity recommendations (<150 min moderate-intensity exercise, <75 minutes of vigorous-intensity exercise, and <2 days of strength training)
  • Not following a diet that is restrictive or eliminates certain food group/types

Exclusion criteria

  • Allergies to nuts, especially tree nuts
  • Has a pacemaker
  • Following a diet that is restrictive or eliminates certain food group/types
  • Self-repoted health or disease state that may influence study outcomes, including known metabolic or endocrine disorder (e.g. prediabetes, type 1 or type 2 diabetes, or polycystic ovary syndrome), cardiovascular diseases, neuromuscular disorders, musculoskeletal disorders; current or recent history of cancer/cancer treatment (within the past year)
  • History of gastrointestinal surgery, hysterectomy
  • For women: pregnant or thinking of becoming pregnant during the time of participation, pregnant within the last year, currently breastfeeding, or known to be perimenopausal

Treatment and study plan

Pistachio

Other

Roasted, lightly salted, pistachio kernels (no shell)

Primary outcomes

  1. resting metabolism

    Time frame: Day 0 and Day 5

    resting metabolic rate (RMR) and substrate utilization (RER) via indirect calorimetry

  2. exercise metabolic flexibility

    Time frame: Day 0 and Day 5

    substrate metabolism (RER; indirect calorimetry) throughout a submaximal, graded exercise test

  3. post-exercise metabolism

    Time frame: Day 0 and Day 5

    Energy expenditure and substrate metabolism (RER) measured at 0, 30, 60, 90min post-exercise via indirect calorimetry

Secondary outcomes

  1. Caloric Intake

    Time frame: Day 0 and Day 4

    Average calorie intake (kcal) via 24-hr diet record

  2. Carbohydrate Intake

    Time frame: Day 0 and Day 4

    Average carbohydrate intake (grams) via 24-hr diet record

  3. Protein Intake

    Time frame: Day 0 and Day 4

    Average protein intake (grams) via 24-hr diet record

  4. Fat Intake

    Time frame: Day 0 and Day 4

    Average fat intake (grams) via 24-hr diet record

Other outcomes

  1. Physical Activity

    Time frame: daily continuous (Day 0 to Day 5)

    Daily (24-hr) steps and intensity minutes via wrist activity tracker

  2. Sleep Quantity

    Time frame: Nightly (Day 0 to Day 5)

    Nightly sleep quantity (total time spent asleep; minutes) via wrist worn activity tracker.

  3. Sleep Quality

    Time frame: Nightly (Day 0 to Day 5)

    Nightly sleep quality (time spent in deep sleep (minutes), REM sleep (minutes), and light sleep (minutes)) via wrist worn activity tracker.

  4. Daytime sleepiness

    Time frame: Day 0 and Day 5

    Subjective likelihood of falling asleep in various situations via Epworth Sleepiness Scale. In this eight question survey, questions are rated on a scale of 0 (very unlikely) to 3 (very likely), with a total score of 0-9 indicating low daytime sleepiness, 10-15 indicating moderate daytime sleepiness, and 16-24 indicating severe daytime sleepiness.

  5. Subjective hunger

    Time frame: Daily (Day 1 to Day 4)

    Degree of hunger/fullness (Visual Analog Scale) mid-morning (post-snack), late morning (a few hours post snack), and mid-afternoon (pre-snack).

Study contacts

Contact information is provided by the study sponsor or research team.

Callie Unrein, MS

CONTACT

[email protected]

803-777-5478

Sponsors and collaborators

Lead sponsor

University of South Carolina

Other

Collaborators

  • American Pistachio Growers

Registry information

Official study title

Effects of Pistachio Snacking on Metabolic Flexibility in Healthy Overweight and Obese Adults

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Jan 14, 2026
Registry last updated
Jan 14, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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