Effects of a Probiotic Formulation Based on SF68, Phytosterols, and 6S-5-Methyltetrahydrofolic Acid on Body Composition, Biochemical Parameters, Gut Microbiota, and Gastrointestinal and General Symptoms of Overweight/Obese Subjects: The PrObesity Study

Obesity and dyslipidemia are increasingly widespread. Considering gut microbiota's (GM) role in energy balance, probiotics represent a promising non-pharmacological approach. This study assessed a probiotic formulation (SF68 + phytosterols + (6S)-5-methyltetrahydrofolic acid) on anthropometric, biochemical, and GM parameters, as well as gastrointestinal and general symptoms, in overweight/obese individuals with low-to-moderate cardiovascular risk. Forty participants (30F, mean age 51.5 ± 11 years) were randomized to receive either the probiotic or placebo daily for 12 weeks. Anthropometric data, questionnaires, and biological samples were collected pre- and post-intervention. While both groups showed significant (p < 0.05) improvements, the probiotic group showed greater reductions in waist circumference (−1.8 cm), fat mass (−1.8 kg; −1.7%), total cholesterol (−11 mg/dL), and LDL-cholesterol (−10.3 mg/dL), along with an increased HDL/LDL ratio (+0.1). Both probiotic and placebo resulted in a significant reduction in HbA1c (−1.7 mmol/mol and −1.5 mmol/mol, respectively). The probiotic formulation also reduced erythrocyte ROS (−29.7%), granulocyte ROS (−28.4%), and plasma nitrite/nitrate (49.5%) and significantly increased erythrocyte glutathione (GSH; +81.9%). Gastrointestinal symptoms improved, and GM analysis showed an increased Evenness index and reduced Lachnospirales abundance after probiotic treatment. These findings suggest the multi-component probiotic formulation may support metabolic and gut health in overweight or obese individuals, although further research is warranted.