Effect of Steamed Onion (ONIRO) Consumption on Body Fat and Metabolic Profiles in Overweight Subjects: A 12-Week Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Objective: The aim of the study is to investigate the effect of Jeju steamed onion (ONIRO) on body fat and metabolic profiles in overweight subjects. Methods: This randomized, double-blind, placebo-controlled clinical intervention was conducted and completed at one clinical research site. The subjects (n = 70) were randomly divided into placebo or test group and were instructed to take before each meal either the placebo or ONIRO capsule for 12 weeks. Anthropometric as well as serum and metabolic parameters, including triglycerides, cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, leptin, adiponectin, C-peptide, and aspartate aminotransferase (AST) were measured at baseline and after 12 weeks. Body composition was also measured by dual-energy x-ray absorptiometry (DEXA) and computed tomography (CT). This trial is registered under the trial registration code clinicaltrials.gov: NCT03645382 (https://register.clinicaltrials.gov). Results: Compared to the placebo, ONIRO supplementation for significantly reduced the percentage of body fat and fat mass as measured by DEXA (p = 0.028 and 0.022, respectively) with no significant effects on lean body mass. CT analyses at the L1 level showed a significant decrease in the areas of whole fat, visceral fat, and subcutaneous fat (p = 0.009, p = 0.039, p = 0.020, respectively), while CT scan of L4 resulted in a significant reduction of whole fat area and subcutaneous area (p = 0.006 and p = 0.012, respectively). The levels of triglycerides (TG) and C-peptide were significantly lower after 12 weeks of ONIRO treatment. Conclusions: These findings suggest that ONIRO supplementation reduces total body fat, notably abdominal visceral fat, with positive changes of the clinically relevant metabolic parameters serum TG and C-peptide.