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.

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

data may be shared upon reasonable request.