Effects of weight loss while feeding a moderate-protein, high-fiber diet on body composition, voluntary physical activity, and blood metabolite profiles in overweight cats

Obesity is a major nutritional disorder in cats and is associated with several comorbidities and reduced life span. The primary objectives of this study were to determine the effects of feeding a moderate-protein, high-fiber diet on BW loss, voluntary physical activity levels, body composition, and blood metabolite profiles in overweight cats. During a 4-wk baseline period, 8 adult neutered male domestic shorthair cats (mean BW = 7.7±0.4 kg, mean BCS = 7.6/9) were fed to maintain BW. For 18 wk following baseline, food intake was adjusted to allow cats to lose weight at a rate of ~1.5% BW/wk. Cats were group-housed for 20 h/d and individually housed for two, 2-h periods each day for feedings. Daily food intake, twice-weekly BW, and weekly BCS were recorded throughout the study. Voluntary physical activity was measured over a 7-d period at wk 0, 6, 12, and 18 using Actical® activity monitors. Dual energy X-ray absorptiometry (DEXA) scans were taken at wk 0, 4, 8, 12, and 16 to estimate body composition. Overnight fasted blood samples were collected at wk 0, 1, 2, 4, 8, 12, and 16. The University of Illinois Institutional Animal Care and Use Committee approved all procedures. As expected, mean BW (7.7±0.4 vs. 6.2±0.4 kg) and mean BCS (7.6 vs. 6.0) decreased (P < 0.05) from wk 0 to wk 18. The NRC (2006) maintenance energy requirement (MER) for overweight cats is 130(BWkg0.40). In comparison, the mean MER during baseline in our study was 113(BWkg0.40). Throughout wk 1-4, 5-8, and 9-18, the energy levels to sustain weight loss were 76, 64, and 57% of baseline MER, respectively, demonstrating how restrictive feeding must be for consistent weight loss. Mean fat mass was decreased (P < 0.001) at wk 8, 12, and 16 (2417 , 2097 , and 1810 g, respectively) versus wk 0 (2924 g); therefore, body fat percentage also was decreased (P < 0.05) at wk 8, 12, and 16 (36.8, 34.0, 30.7%, respectively) versus wk 0 (40.9%). Mean lean body mass was lower (P < 0.01) at wk 12 and 16 (3671 and 3664 g, respectively) versus wk 0 (3865 g). Importantly, lean body mass percentage was increased (P < 0.05) at wk 8, 12, and 16 (61.5, 64.4, and 67.6%) versus wk 0 (57.6%). Mean daily activity tended to be higher (P = 0.061) at wk 12 vs. wk 0. The mean light:dark ratio of activity was increased ( P <0.05) at wk 18 vs wk 0, 6, and 12. Except for elevated mean creatinine (P < 0.05) during weight loss, all blood metabolites remained within reference ranges. Mean triglyceride concentrations were decreased (P < 0.05) throughout the weight loss phase. Using non-targeted gas chromatography, liquid chromatography, and mass spectrometry, a total of 535 named biochemicals were identified, with up to 269 metabolites altered (P- and q- values < 0.05) at any time point. Principal component analysis showed a continual shift in metabolite profile as weight loss progressed. Components 1 and 2 explained 14.3% and 10.3% of the variability, respectively. There was a significant and dramatic reduction of bile acids (cholate; taurocholate; deoxycholate) with weight loss. A reduction in numerous non-esterfied fatty acids (NEFA) and an increase in ketones (acetoacetate; 3-hydroxybutryate) and monoglycerides suggested a shift toward lipolysis and hepatic NEFA oxidation. Decreased markers of inflammation and oxidative stress were indicated by reduced pro-inflammatory oxylipids, eicosanoids, and oxidized biomarkers following weight loss. Mevalonate was decreased (P < 0.05) after wk 8 compared to baseline, which agrees with the reduced bile acids without altering cholesterol concentration. In conclusion, restricted feeding of a moderate-protein, high-fiber diet is a safe and effective means for weight loss in cats, leading to increased physical activity and reduced blood triglycerides. Global metabolomics identified biomarkers of reduced food intake, weight loss, and/or altered metabolism. Based on our data, the current NRC (2006) MER estimates for cats appear to be too high and should be reconsidered