Cats are strict carnivores and have a high dietary protein requirement. Rich-protein diets are often intended to prevent obesity or manage weight loss, as they help preserve the lean body mass. The aim of this study was to assess the effect of an experimental high-protein low-carbohydrate maintenance dry diet (HP) on body composition (BC), compared with a commercial moderate-protein high-carbohydrate dry diet (MP) in neutered cats. Twelve (12) young adult neutered cats (19.6 ± 0.4 mo old; 3.56 ± 0.2 kgBW) were randomized in 2 groups and received, for 20 weeks, either a HP (3,320 kcal/kg of DM; 50.2 CP %DM) or a MP (3,590 kcal/kg of DM; 33.7 CP %DM) diet. Main protein sources and amino acid content (DM basis) were: HP diet: meat meal, pea; Lys 2.3%, Met 1.0%, Try 0.4%, Thr 1.7%; MP diet: poultry meal, corn gluten meal, corn; Lys 2.0%, Met 1.0%, Try 0.3%, Thr 1.3%. Animals were fed according to their estimated energy requirement to maintain their BW. Body composition (BC) was determined using deuterium oxide dilution at the beginning then at the end of the study. Tukey’s test was used to detect the effect of each diet and a Wilcoxon test to evaluate the differences between groups, with a 5% significance level. The mean protein intake during the study was 7.2 ± 0.6 g/kgBW/d in the HP group, and 4.6 ± 0.3 g/kgBW/d in the MP group. On d 1, the 2 groups were similar regarding their BW and BC. In both groups, no change in BW was observed. BC was unchanged in the HP group whereas body fat mass increased (P < 0.05) and lean body mass decreased (P < 0.01) in the MP group. The lean mass/fat mass ratio changed from 74/26 to 75/25 and from 77/23 to 69/31, in the HP and MP groups respectively. Although the protein content of the MP diet was higher than the recommended allowance (20% ME according to NRC 2006), it appeared not high enough to maintain lean body mass in these cats. Our results are in accordance with another study showing that adult cats would require at least 5.2 g protein/kg BW/d to maintain their lean body mass.