Overview: You are invited to participate in a research study. You can join if you are a woman, 18-40 years old, have a BMI >25, and a regular menstrual cycle (every 24 to 38 days, per the Cleveland Clinic). This study is open to the TCU and non-TCU communities. You cannot join if you:

• Have diagnosis of diabetes or take insulin or metformin.
• Have either diagnosis of high blood pressure, is currently taking high blood pressure medications, or shows high blood pressure readings during visit 1 ≥130/80 mmHg.
• For the past month, have engaged in >150 min/week of moderate intensity aerobic exercise (brisk walking), >75 min/week of vigorous-intensity aerobic activity (running, fast cycling), and ≥1 session/week of strength exercising using weights for the past month.
• Have lost or gained 10% or more of your body weight in the past 3 months.
• Have used antibiotics or probiotics in the past 3 months.
• Follow a restrictive diet like vegetarian, vegan, keto, or carnivore.
• Take weight loss medications or supplements.
• Smoke (including vaping) or drink heavily (more than 8 drinks per week for women, per CDC guidelines).

Study Details: This study is being conducted at Texas Christian University, Richel building 256 and 259. The project is sponsored by a Texas Christian University Invests in Scholarship grant. The purpose of this study is to looks at how gut bacteria affect exercise benefits. We want to see if a supplement called butyrate can help people who don't get better insulin response from exercise. Butyrate is a natural substance made by gut bacteria when they break down fiber in your diet. The study lasts 12 weeks, including a 12-week supervised exercise program (30-60 min per day/5 days per week), 4 weeks of taking a butyrate supplement daily (weeks 8 to 12), 3 material pick up visits (10 min each) and 3 lab visits (60 min each). All participants will follow the 12-week exercise intervention and all participants will follow the 4-week supplementation.

Participants: You are being asked to take part because you're a woman aged 18-40 with a BMI of 25.0 or higher and have regular menstrual cycle (every 24 to 38 days, per the Cleveland Clinic). You must not have done regular exercise (less than 150 minutes of moderate activity, 75 minutes of intense activity, or 1 session of strength training per week) for the past month and have no recent competitive sports experience. If you decide to be in this study, you will be one of 40 participants in this research study at TCU.

This is a single-arm, interventional study investigating the role of the gut microbiome in mediating the effects of cardiovascular exercise on insulin sensitivity in adult females with overweight or obesity (BMI ≥25). The study also evaluates the effectiveness of sodium butyrate supplementation in enhancing insulin sensitivity among individuals who are otherwise non-responsive to exercise alone.

The study will enroll 40 female participants between the ages of 18 and 40, who have been sedentary for at least six months. Exclusion criteria include a diagnosis of diabetes or hypertension, recent weight changes, use of antibiotics, probiotics, or weight loss supplements, and any condition contraindicating safe participation in exercise.

Participants will engage in a 12-week supervised cardiovascular exercise program at the TCU Recreation Center. Exercise will progress from 30 to 60 minutes per session, 5 days per week, with intensity increasing from 50% to 80% of estimated maximum heart rate. During weeks 8 through 12, participants will take sodium butyrate (BodyBio; 939 mg sodium/day) in capsule form, dosed at 2 capsules with each meal (6 total/day).

Data collection includes:

• Stool samples (3 total): collected pre-intervention, at week 8 (pre-supplementation), and at week 12 (post-supplementation), to evaluate changes in gut microbial composition and diversity.
• Blood samples (3 total): fasting blood draws at the same three time points to measure glucose and insulin for calculation of HOMA-IR and other insulin sensitivity indices.
• Body composition: assessed at three time points using Dual-Energy X-ray Absorptiometry (DEXA) to determine fat mass, lean mass, and bone mineral density.
• Questionnaires: validated instruments assessing physical activity, dietary intake, sleep, anxiety, depression, and food cravings.
• Blood pressure: at the beginning of the study, and every week during the supplementation phase

The primary outcomes include changes in insulin sensitivity and gut microbiota composition across the 12-week intervention. Secondary outcomes include body composition changes and the classification of participants as "responders" or "non-responders" to exercise based on insulin sensitivity improvements.

An exploratory objective is to develop predictive models using AI algorithms (e.g., decision trees, random forests, support vector machines, logistic regression) trained on baseline gut microbiota and blood biomarkers to predict individual response to exercise.

This study is internally funded by a TCU Innovation Scholars (IS) Grant (~$20,000), with an in-kind supplement donation valued at $2,000 provided by BodyBio. The study is conducted entirely on the TCU campus and has been approved by the TCU Institutional Review Board (IRB #2025-217). Results from this study aim to advance personalized exercise strategies and contribute to the growing field of precision medicine.

Inclusion Criteria:

• BMI greater than or equal to 25: A BMI at or greater than 25 classifies an individual as having overweight or obesity, which is the population we are looking for in this study.
• Female individuals with regular menstrual cycles (every 24 to 38 days, per the Cleveland Clinic): For this pilot study, we are limiting participation to female individuals, as our sample size is insufficient to investigate sex differences in gut microbiome interactions, which our prior experience suggests are significant. The menstrual cycle is controlled for as it can affect insulin resistance values, which is one of our main outcome variables.
• Age 18-40 years: Limiting the age range helps reduce age-related variability in metabolism, hormonal profiles, and gut microbiota composition. Adults under 40 are less likely to have comorbidities or take medications that could confound results. This age range also ensures participants can legally consent and likely have the cognitive capacity to understand and comply with study procedures.
• Willingness to maintain current diet: Diet has a strong influence on metabolic and microbiome outcomes. Requiring participants to maintain their habitual diet reduces a major source of variability and allows for clearer attribution of observed effects to the intervention being studied
• Desire/ability to understand and complete forms in English: To ensure informed consent and data accuracy, participants must be able to understand study materials, instructions, and questionnaires.
• Willingness to participate in a 12-week exercise intervention.

Exclusion Criteria:

• Having diabetes of any kind and/or currently being prescribed insulin: Diabetes significantly alters metabolic processes and gut microbiota, which may confound the outcomes of interest. Insulin therapy can independently affect weight, glucose regulation, and inflammatory status. Excluding individuals with diabetes ensures a more metabolically uniform sample and avoids the need for complex medical monitoring
• Having a diagnosis of high blood pressure, currently taking high blood pressure medications, or having high blood pressure readings during visit 1 ≥130/80 mmHg
• Current participation in regular exercise or participation in the last month (> 150 minutes of moderate activity, 75 minutes of intense activity, or more than 1 session of strength training per week): Regular physical activity affects weight, metabolism, insulin sensitivity, and gut microbiota. Including only untrained participants minimizes variability and allows a clearer assessment of the study intervention's effects without confounding from exercise-related physiological changes.
• Recent significant weight change (weight loss or gain of ≥10% of body weight in the last 3 months): Substantial recent weight gain or loss may signal underlying health changes, dietary shifts, or medication use that could influence study outcomes. It also complicates baseline comparisons and longitudinal measures. Stable weight ensures physiological stability and data consistency.
• Use of antibiotics or probiotics in the last 3 months: Antibiotics can drastically alter the gut microbiome for weeks to months, and probiotics may modulate microbial composition and metabolic markers. To isolate the effects of the study intervention, participants must have a stable, unaltered baseline microbiota.
• Current pregnancy or planning to become pregnant during the study duration: Pregnancy induces major hormonal, metabolic, and microbiome changes, making it a strong confounder. For safety and scientific clarity, pregnant individuals are excluded to avoid complications and ensure data homogeneity.
• Currently lactating: Lactation also involves significant hormonal and metabolic shifts. These physiological changes could confound outcomes related to metabolism, weight, or microbiota composition.
• Following a vegetarian, vegan, keto, carnivore, intermittent fasting, inconsistent time-restricted feeding, or another restrictive diet: Restrictive diets strongly influence gut microbiota, energy metabolism, and nutrient absorption. Excluding individuals on these diets helps control for dietary variability and standardize the nutritional background of participants.
• Currently taking weight loss medications (such as GLP-1 receptor agonists) or supplements: These medications and supplements can alter appetite, weight, metabolic markers, and microbiome composition. Their use could obscure the effects of the study intervention, so exclusion improves internal validity.
• Smoking, vaping, or excessive alcohol use (e.g., >14 drinks/week for men, per CDC guidelines): Tobacco and excessive alcohol use are associated with systemic inflammation, metabolic changes, and altered gut microbiota. Excluding these individuals reduces health-related confounding and protects participant safety
• Inability to understand and/or complete forms in English: Accurate completion of study forms, consent, and assessments is essential for reliable data collection. If forms are only available in English, participants must be proficient to ensure informed consent and study integrity.

Biological Female Participants

We plan to conduct additional analyses using the samples and data collected in this study beyond the primary aims described in this trial. However, if no further use is identified after the study and initial data analysis are complete, individuals may request information about data sharing by contacting Dr. Elisa Marroquín.