Effects of a Low-Fat Diet Supplemented with Plant Extract on Lipid Metabolism, Antioxidant Capacity, Inflammation, and Gut Microbiota in Healthy Beagles

Obesity has become a major disease in dogs and cats. Dietary management is a preventive measure because controlling energy intake (e.g., portion size and diet energy density) helps maintain an ideal BCS and reduces the likelihood of progressive weight gain and associated metabolic abnormalities. This study evaluated a low-fat diet, with or without plant-extract supplementation, and its effects on serum biochemistry, lipid metabolism, gut microbiota, and metabolic profiles in healthy beagles. Thirty beagles were randomly divided into three groups (n = 10 per group): a conventional diet (Group A), a low-fat diet (Group B), and a low-fat diet supplemented with plant extract (Group C). The experiment lasted for a total of 9 weeks, comprising an adaptation period of one week and an experimental period of eight weeks. Results showed that, compared with Group A, the low-fat diet interventions (Groups B and C) significantly reduced serum levels of triglycerides, low-density lipoprotein, and total bile acids (p < 0.05). Furthermore, superoxide dismutase activity was significantly higher in Groups B and C than in Group A (p < 0.05). Compared with both Groups A and B, Group C exhibited significantly lower malondialdehyde levels, reduced proinflammatory cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6; p < 0.05), and decreased serum diamine oxidase activity and lipopolysaccharide levels (p < 0.05). The gut microbiota analysis revealed that Group C had a significantly increased relative abundance of beneficial bacteria, such as Lactobacillus (p < 0.05). Metabolomic analysis further indicated that beneficial metabolites, including γ-aminobutyric acid and glutamine, were significantly upregulated in Group C (p < 0.05). In conclusion, while a low-fat diet effectively regulated serum lipids in healthy dogs, the supplementation of a blended extract from Atractylodes lancea, Magnolia officinalis, and Citrus reticulata Blanco demonstrated broader efficacy. It further improved lipid metabolism, systemic antioxidant status, and intestinal barrier function, while attenuating inflammation and enriching beneficial gut microbes (Lactobacillus) and metabolites (GABA and glutamine). These findings suggest that while a low-fat diet alone is beneficial, its combination with plant extract provides a novel dietary strategy for promoting lipid metabolism and potentially reducing obesity-related disease risk in dogs.