The Effects of a Novel Combination of a Probiotic Supplement (L. Rhamnosus Gg, L. Acidophilus, and L. Casei) With a Weight Gain Intervention on Body Composition, Appetite, Gut Permeability, Oxidative Stress, and Inflammation in Underweight Adults: Study Protocol for a Double-Blind, Randomized Controlled Trial Publisher



Hatami A ; Ahmadi Khorram M ; Afshari A ; Ghannadzadeh Yazdi A ; Esfehani A J ; Jarahi L ; Masoumvand M ; Philippou E ; Nematy M
Source: BMC Nutrition Published:2026

Abstract

Introduction: Undernutrition, characterized by insufficient energy and protein intake and/or malabsorption, leads to adverse physical and mental health outcomes. Addressing Undernutrition is complex, requiring adequate dietary intake and consideration of the gut microbiota, which is crucial for nutrient absorption and metabolism. Probiotics have shown potential in restoring the gut microbiota balance, enhancing nutrient absorption, and improving growth and immune function. The proposed double-blind, randomized controlled trial (RCT) aims to evaluate the effects of a novel probiotic combination in conjunction with a weight gain intervention on body composition, appetite, gut permeability, oxidative stress, and inflammation in severely underweight adults. Methods: A double-blind, randomized controlled trial in which 100 underweight (BMI < 18.5 kg/m2) adults will be recruited and randomly assigned to receive either a probiotic combination (Lactobacillus rhamnosus GG, Lactobacillus acidophilus, and Lactobacillus casei) or an identical placebo alongside a weight gain dietary intervention providing an additional 500 kcal/day for eight weeks will be performed. The primary endpoint will be the difference in body mass index (BMI), calculated as weight/height2 (kg/m2), between the two groups. The secondary endpoints include (1) body composition evaluated by bioelectrical impedance, (2) appetite evaluated via a visual analog scale, (3) gut permeability assessed by the serum zonulin concentration, (4) oxidative stress evaluated by the serum concentration of malondialdehyde (MDA), total antioxidant capacity (TAC), total oxidant status (TOS), glutathione peroxidase (GPx), and inflammation assessed via the C-reactive protein (CRP) level and erythrocyte sedimentation rate (ESR), (5) bowel function assessed via the Bristol stool chart, and (6) dietary intake evaluated via 24-h dietary recall. Discussion: This study outlines a comprehensive approach to investigating the impact of probiotics in combination with dietary intervention on multiple health parameters in underweight adults. The results of this trial will contribute to further ways of managing malnutrition. Ethics and dissemination: This study was approved by the Ethics Committee of the Research Vice-Chancellor at Mashhad University of Medical Sciences (IR.MUMS.MEDICAL.REC.1401.589) (IR.MUMS.MEDICAL.REC.1402.057). All participants will be asked to complete the consent form at the beginning of the study. The results will be actively disseminated through peer-reviewed journals and conference presentations. Trial registration {2a and 2b}: Iranian Registry of Clinical Trials, IRCT20230310057667N1 (Issue date 30 March 2023), https://irct.behdasht.gov.ir/trial/69130. © The Author(s) 2026.