Dog and cat nutritional requirements are different from one another and among its own kind. They need precisely balanced nutrition for their specific life stage, and special needs to stay healthy. Body Mass Index (BMI) is use in human as a screening tool to identify possible weight problems. While, Body Condition Scoring (BCS) is use to check your pet's body condition and ideal size. An underweight or overweight pet requires special attention from the veterinarian, as it may indicate inappropriate or insufficient nutrition, or even underlying disease.