Soy Sauce Lowers Body Weight and Fat Mass in High-Fat Diet-Induced Obese Rats

Soy sauce (SS) is a traditional fermented seasoning. Although fermented foods have diverse health beneficial effects, SS intake has been discouraged because of its high salt level. This study was designed to evaluate the antiobesity outcomes of SS and the potential involvement of salt content in SS by adding a high-salt group. Sprague-Dawley rats were randomly assigned into four groups: normal diet (ND, 10% fat of total kcal), high-fat diet (HD, 60% fat of total kcal), HD with salt water (HDSW, NaCl = 8%), and HD with SS (HDSS, NaCl = 8%). SS significantly decreased HD-induced body weight gain and lipogenic gene expression without affecting food consumption. Moreover, SS also reduced hepatic injury and lipid accumulation, and also improved hyperlipidemia. Furthermore, SS decreased the mRNA levels related to obesity-derived inflammatory responses, while HDSW did not change the levels of those markers. These observations indicate that SS ameliorates obesity in HD-fed obese rats by attenuating dyslipidemia. Moreover, SS might also have an anti-inflammatory effect in HD-induced obesity, which requires further investigation. Most importantly, SS offers these beneficial effects regardless of its high salt content, implying that different dietary salt sources lead to the distinct health outcomes. In conclusion, the findings of this study improve the understanding of the functional effect of SS.