291 Isoenergetic reduction of dietary macronutrients changes body composition and physical activity in cats, regardless of body condition, when fed to maintenance

Abstract Commercial extruded cat foods deviate noticeably from the natural diet of wild cats and contain greater carbohydrate and less protein. This alteration in macronutrient distribution is postulated as a potential factor in feline obesity, yet the precise role of carbohydrates in either predisposing to, or treating, obesity in cats remains inconclusive. This study explored the effects of diets differing in protein, fat, and carbohydrates (NFE) on physical activity and body composition when fed to adult male cats to maintain body weight (BW). Three extruded diets were formulated for adult maintenance according to AAFCO in an isoenergetic approach using the same ingredients in varying proportions: low-protein (LP; protein 28% of metabolizable energy [ME], fat 40% ME, NFE 32% ME), low-fat (LF; protein 42% ME, fat 30% ME, NFE 30% ME), or low-carbohydrate (LC; protein 36% ME, fat 41%ME, NFE 23% ME). Lean (n = 9) and obese (n = 9) adult male neutered cats were fed each diet for 4-wk in a 3 x 3 Latin square design. Physical activity was measured via actigraphy on d 15 to 21 of each period. On d 23 total tissue mass (TTM), body fat mass (BFM), lean soft tissue mass (LSTM), and bone mineral content (BMC) were assessed by dual energy x-ray absorptiometry. Daily food intake and weekly BW were recorded. Data were statistically analyzed in SAS Studio via the GLIMMIX procedure with diet and body condition (bc) as fixed effects and cat as subject. A Tukey post-hoc analysis was performed to assess multiple comparisons when significant (P < 0.05). Body weight (Pbc < 0.0001), TTM (Pbc < 0.0001), BFM (Pbc < 0.0001), LSTM (Pbc < 0.0001), and BMC (Pbc = 0.004) were greater in obese compared with lean cats. Regardless of body condition, LSTM was greater in cats consuming the LF diet (P = 0.010). Daily physical activity was similar between lean and obese cats; however, activity as a ratio of light:dark activity was greater for lean cats compared with obese (Pbc = 0.027). Additionally, cats were more active during dark hours when fed LC and LF (Pdiet = 0.016), though no difference was observed for activity during light hours (P = 0.452). These findings support previous observations regarding body composition disparities between lean and obese cats. Contrary to previous reports, no discernible distinctions in voluntary physical activity were noted between lean and obese cats. In previous studies, both high-carbohydrate and high-fat diets reduced voluntary physical activity when fed to maintain BW which was attributed to a potential alteration in mood and energy levels seen in other species. An increase in physical activity in cats consuming the LF diet could suggest a similar pattern. Future research should explore the metabolic implications of varied macronutrient distributions to expand upon the physiological insights presented herein. Funding for this study was provided by Champion Petfoods, Mitacs Accelerate, and the Natural Sciences and Engineering Council of Canada.