The proposed clinical trial will test our hypothesis that, during exercise, red blood cell (RBC) release of heme and catabolism to bilirubin is an essential process that mediates gene responses that reduce body fat. We will evaluate whether Milk Thistle extract or Lactobacillus Gasseri extends bilirubin circulating times to decrease body fat further. Thus we will perform a 12-week, 6-armed trial with one group performing aerobic exercise 5 times per week (EX) one group receiving a Milk Thistle extract (MT), one group receiving a lactobacillus gasseri supplement (LAC), a group receiving only a placebo (CON), and groups both exercising and receiving the MT (MT + EX) and lactobacillus and exercise (LAC + EX).

The investigative team's previous work has shown that BR binds to the PPARalpha protein in fat and liver tissues to activate genes that improve fatty acid oxidation via a hormone known as fibroblast growth factor-21 (FGF21). The investigators recently showed that in high capacity running rats (HCR) compared to low capacity running (LCR), in which the latter are obese, BR levels and PPARalpha-FGF21 were significantly raised in the high-capacity runners. New investigations have shown that Milk Thistle (MT) herbal supplement contains polyphenols that activate pathways that suppress the glucuronyl enzyme UGT1A1 that removes BR from the blood, improving liver function and moderately increasing BR blood levels by ~2-fold. Similar findings have been demonstrated with Lactobacillus Gasseri supplementation. Hence, there is a bilirubin-PPARalpha-FGF21 axis that can be driven by exercise and dietary supplementation. We will test whether exercise and milk thistle or exercise and lactobacillus gasseri synergistically increase bilirubin-PPARalpha-FGF21, further reducing body fat in patients with obesity.

Participants in the EX, EX + MT, and EX + LAC groups will complete five weekly exercise sessions on their own, expending roughly 600 kcal per session. Participants will be provided a Polar A-300 heart rate monitor programmed for their individual attributes (height, weight, age, training status, gender), which gives a real-time estimate of energy expenditure during exercise. Participants will report to the lab once per week to download the exercise sessions and verify compliance. If participants are not compliant (defined as completing 85% of their assigned exercise sessions per month), they will be disqualified. This intervention has been successfully used by the investigators in multiple studies to produce significant weight loss without dietary intervention in this population with a retention rate of over 90% Participants in the MT and EX + MT groups will be provided 900 mg of standardized milk thistle extract daily (300 mg three times per day before meals) over the 12-week regimen. The investigators will use the standardized Jarrow Formulas Milk Thistle Veggie Caps containing 30:1 extract that is standardized to contain 80% total Milk Thistle seed flavonoids (polyphenols), including the critical Silymarin fractions isosilybinins A and B, silybinins A and B, silychristin and silydianin that is active against suppressing the UGT1A1 enzyme increasing plasma bilirubin. The capsules are free of wheat, gluten, soybeans, dairy, egg, fish/shellfish, peanuts/tree nuts, and GMOs. Rationale for using this brand: There have been inconsistencies with previous studies that did not use a standardized silymarin extract, which may have contained low levels of the active polyphenolic flavonoids in the milk thistle plant, which varies in the plant's stems, leaves, roots, and flowers.

Participants in the LAC and LAC + EX groups will receive two doses of 3 billion CFU of lactobacillus gasseri per day for a total of 6 billion CFU, the recommended upper level for supplementation of probiotic cultures. The Swanson brand Lactobacillus gasseri will be used, as these capsules are also free of wheat, gluten, soybeans, dairy, egg, fish/shellfish, peanuts/tree nuts, and GMOs. Importantly, this brand uses acid-resistant designed release capsules to improve the viability of the lactobacillus in the human stomach.

Participants in the CON and EX group will receive a placebo (maltodextrin) made to look identical to the MT capsules.

Inclusion Criteria:

• Classified as obese (BMI 30-45)
• Sedentary (do not currently exercise)
• Aged 18-50 years
• Without contraindications to exercise

Exclusion Criteria:

• Dieting for weight control
• Tobacco users
• Have a ragweed allergy
• Taking antibiotics, hypoglycemic agents, anticoagulants, statins, or NSAIDs
• Nursing, pregnant, or planning on becoming pregnant
• Supplementing with a probiotic

unidentified participant data will be shared on figshare data repository

Within 6 months of study completion data, for 5 years.

available to public, has not been created yet

Participants nor research staff working with them will know what supplement they are receiving.