This study investigates the role of dietary protein levels in sparing lean body mass in 42 overweight dogs during weight loss programs aimed for a 1% weekly loss until optimal body condition score was achieved. Three diets with different protein levels (20, 30 and 39% of calories from protein) were used, and body composition of dogs was determined by DEXA before the diets and after reaching the optimal BCS. The greatest loss of body fat and preservation of lean body mass was achieved with increasing protein levels. At least, 30% of calories should be provided by protein during canine weight loss programs.