Background: The purpose of the present study was to clarify the efficacy of soy at reducing visceral fat. A randomized, double-blind, controlled, comparative trial was carried out to compare formula food containing soy protein (SP) to the same food in which soy was replaced with milk protein (MP).
Methods and results: Forty-eight participants were enrolled for the treatment of visceral fat obesity (visceral fat area >100 cm² on computed tomography). The SP formula contained 12 g of SP, 9 g of MP, and other nutrients, and was given for 20 weeks in the morning, while in the MP formula SP was replaced with MP. During the 20 weeks of the trial period, visceral fat area and subcutaneous fat area in the MP group were significantly reduced, while those in the SP group did not change as assessed on analysis of covariance. Although waist circumference was reduced in both the SP and MP groups, body weight and body mass index were significantly reduced only in the MP group. Based on a mixed-effects model, the difference in log-transformed visceral fat profiles between the 2 groups was statistically significant (P<0.05), while a negative relationship was observed between the changes in visceral fat and adiponectin in the MP group (P<0.001), but not in the SP group.
Conclusions: Formula food containing MP is superior to that containing SP for reducing visceral and subcutaneous fat.