Visceral Fat-Reducing Effect of Novel Dietary Intervention Program: A Randomized Controlled Trial in Japanese Males

Background/Objectives: Reducing visceral fat is a critical factor in preventing obesity-related health complications. In this study, we evaluated the effectiveness of our previously reported novel dietary intervention program, "Optimized Nutri-Dense Meals", designed according to the Dietary Reference Intakes (DRIs) in Japan in reducing visceral fat. Method: This open-label, randomized controlled trial included 100 Japanese males with obesity or overweight. In total, 50 participants were assigned to a control group that continued their usual diets, and the other 50 consumed test meals twice per week for four weeks (test group). Result: The primary outcome, visceral fat area, significantly decreased in the test group compared to that in the control group (-7.5 cm², confidence interval [CI]: -14.3 to -0.6). In addition, we measured the changes in gut flora and work productivity. The abundance of Bifidobacterium (+1.5%, CI: 0.3-2.7) and Christensenellaceae (+0.4%, CI: 0.01-0.8) increased significantly in the test group compared with those in the control group. Work Limitation Questionnaire Japanese version scores representing presenteeism also significantly increased in the test group (+1.2 points, CI: 0.2-2.3) compared with the control group. Conclusions: These findings suggest that dietary interventions based on Japanese DRIs can effectively decrease visceral fat and improve health outcomes over the short term without the need for a complete dietary overhaul.