Abstract: Background: The “carbohydrate ceiling” theory proposes that cats may limit food intake on high starch (HS) diets, may helping to maintain a stable body weight (BW) when fed ad libitum. Hypothesis/Objectives: To compare the ad libitum intake of two kibble diets with different starch to protein ratios (but similar in fat and fiber) on BW and composition (BC), and energy expenditure (EE) of privately owned cats. Animals: Female (F) Non-Obese (NO), 2.9±2.1 years (n=9); F Obese (OB; body condition score ≥ 7), 4.2±1.6 years (n=7); Male (M) NO, 2.0±1.1 years (n=9); M-OB, 4.5±2.6 years (n=5). Methods: In a crossover design, cats were fed ad libitum for 4 months a HS (starch 40%, protein 38%) or high protein (HP: starch 20%, protein 55%) kibble diet. The BC and EE were evaluated by the doubly labeled water method. Results were submitted to ANOVA in a 2 diets x 2 sex x 2 BC arrangement (P≤0.05 significant; P≤0.10 trend). Results: Cats fed HS diet maintained constant BW (P>0.05), but lean mass (LM) tended to reduce in F-OB (P=0.07; numerically lower EE and protein intake). The BW and LM of cats increased when fed the HP diet (P< 0.05), but also fat mass in 17% on F-NO (P=0.04) and 7% in F-OB (P=0.06). The EE tended to be higher in M (351±8 kJ/kg0.67/day) than F (330±8; P=0.06) and decreased then cats become older (P< 0.01; Figure 1). Conclusions: In ad libitum feeding system, the intake of HS diet favored a better control of the cat’s BW.
