This question is asked regularly. The answer is quite simple: it depends. It depends on the amount of calories in the food, the total amount of calories consumed in a 24 hours period, the amount of calories expended in the same time frame, and of course genetics. Genetics is probably the most important factor. The same is true in humans. Genetics dictates metabolism and exercise affects how the calories are used. Each dog and cat may require a different amount of calories to survive and hopefully thrive. In the last decade all veterinarians in small animal practice are faced with a growing number of dogs and cats with obesity problems. It has been reported that over 50% of all dogs and cats in the U.S. are overweight or obese. A dog or cat is overweight if it is 5% to 19% above its ideal weight, 20% or more indicates obesity. The overall health status of our pets is also directly related to the level of excess weight being carried, the quality of food being fed, and the veterinary care being provided. A deficiency of one or more of these things can result in serious complications. These include: diabetes, osteoarthritis, anterior/posterior cruciate rupture, cardiac disease, liver disease, respiratory conditions, heat and exercise intolerance, skin and hair problems, and diseases preventable by proper veterinary care. Researchers have reported that some cancers are weight related. The guidelines on the packages of pet foods of how much to feed are just guidelines, no more. The amount should be tailored to how the dog or cat is maintaining its weight on that specific food. Certain breeds are more prone to obesity such as Labradors, Golden Retrievers, Beagles and Cocker Spaniels. In cats, the domesticated strays as well as most of the pure breeds can have a weight problem. Note: you never see a fe ral cat, lion, tiger, wolf, etc. that is fat. They are always hunting and get plenty of exercise. So, tailor the type of food and the quantity and quality to how your pet looks. Don’t forget, treats are also full of calories. You should barely see or feel the ribs, and the abdomen should tuck in just behind the last rib. In my experience, the best food for weight reduction on the market is a prescription product made by Purina called OM. It is palatable and most dogs and cats like to eat it.