BACKGROUND: Consumption of a high-fat, high-carbohydrate Western-style diet (WD) associated with obesity and inflammation in humans has not been investigated in dogs. AIMS: To determine the effects of WD on inflammatory indices, microbiome, and fecal bile acids (BAs) in dogs. ANIMALS: Ten adult clinically healthy dogs. METHODS: A dietary trial compared the effects of two home-prepared diets: a high-fiber, low-fat control diet (CD) to a diet containing the macronutrient composition of WD (low-fiber, high fat). Dietary treatments were given sequentially for three feeding periods, each lasting 1 month. Outcome measures included molecular/microbiologic testing of colonic biopsies, histopathology, inflammatory biomarkers, and quantification of fecal BA following each feeding period. RESULTS: Cell markers of apoptosis (TUNEL-positive cells: CD1, 0.36% ± 0.2%
WD, 0.79% ± 0.5%
CD2, 0.42% ± 0.3%
95% CI) and inflammation (NF-ĸB area: CD1, 8.09% ± 3.3%
WD, 11.58% ± 3.4%
CD2 7.25% ± 3.8%
95% CI), as well as serum high-sensitivity C-reactive protein (CD1, 2.0 ± 0.4 ng/mL
WD, 2.76 ± 0.23 ng/mL
CD2, 2.29 ± 0.25 ng/mL
95% CI), were increased (p <
0.05) in dogs fed WD versus CD. Other perturbations seen with WD ingestion included altered (p <
0.05) colonic mucosal bacteria (bacterial counts: CD1, 301.5 ± 188.5
WD, 769.8 ± 431.9
CD2, 542.1 ± 273.9
95% CI) and increased (p <
0.05) fecal cholic acid (median and interquartile range/IQR: CD1, 9505 [2384-33 788] peak heights
WD, 34 131 [10 113-175 909] peak heights) and serum myeloperoxidase (CD1, 46.98 ± 16.6 ng/mL
WD, 82.93 ± 33.6 ng/mL
CD2, 63.52 ± 29.5 ng/mL
95% CI). CONCLUSIONS AND CLINICAL IMPORTANCE: WD fed to clinically healthy dogs promotes colonic dysbiosis, altered fecal BA, and low-grade inflammation independent of obesity.