After surveying 2.5 million dogs and 500,000 cats in the U.S. last year, a group of researchers found that about one in three were overweight or obese. "Looking over data from the last decade, the researchers say the new figures reveal a 169-percent increase in hefty felines and a 158-percent increase in chunky canines," reports Ars Technica. From the report: All the data is from researchers at Banfield, which runs a chain of veterinary hospitals across 42 states. The researchers surveyed animals that checked into one of Banfield's 975 locations, putting them through a five-point physical and visual exam. Animals were considered overweight if their ribs were not clearly visible or easily felt and if their waists were also hard to see. Pets were dubbed obese if their ribs couldn't be felt at all and they had no visible waist. As in humans, being overweight makes pets more prone to chronic health conditions. Also similar to humans, doctors blame pets' weight problems on overfeeding and lack of exercise. Other contributing factors include genetics and health issues such as arthritis, which can make play painful. Last, some pet owners may not be able to spot weight issues in their pets -- particularly because so many more dogs and cats are now overweight, making chubby pets the new norm. Dog breeds with the highest prevalence of obesity are Labrador Retrievers, Cairn Terriers, and Cocker Spaniels, the researchers report. For cats, the fattest breeds are Manx and Maine Coons.