Obesity is the excessive accumulation of adipose tissue (FAT). It occurs due to an imbalance of energy intake versus energy expenditure. In general pets are defined as overweight when their body weight is 15% over their optimal body weight. They are obese when they are 30% over their optimum. Five extra pounds on a cat is equal to about 44 pounds on a human being! Using these criteria, the prevalence of obesity in dogs and cats in the United States has reached epidemic proportions, between 30% and 40%. Unfortunately there is evidence that the incidence of obesity is increasing despite many tools and programs for diet and exercise to control weight today.
Historically, the functions of fat have been understood as energy storage, thermal insulation, and structural support for internal organs. It is now known that fat is metabolically active and is therefore the largest endocrine organ in the body. The primary reason for development of obesity is that they are consuming more energy than they are expending. This can occur when an animal has excessive dietary intake of calories (all food and treats) or when there is a decrease in energy expenditure (illness or injury). There are some medical conditions (hypothyroidism, etc.) and medications (steroids, etc.) that contribute to obesity.
There are a number of problems found in obese animals compared to ideal body weight animals such as increased anesthetic risk, heat intolerance, orthopedic diseases, diabetes mellitus, heart disease, certain cancers, urethral incompetence and lower urinary tract disease, dyspnea, dystocia, prolonged surgical procedures and increased difficulty with palpation, catheter placement and imaging. As of yet we do not have a complete understanding of the inflammatory role of obesity hormones in out pets, which could lead to a greater connection between obesity and disease.Genetics can play a role although it needs further investigation. We know specific dog breeds are likely to become over weight such as, golden retrievers, cocker spaniels, dachshunds, Labrador retrievers, Rottweilers and Dalmatians. In cats most mixed breeds (DSH, DLH, etc) and Manx cats were more likely to be obese that most purebred cats.
In both dogs and cats, neutering is an important trigger. Neutered dogs are about twice as likely to be overweight than intact dogs. The hormonal changes that occur post-neuter result in increased appetite but decreased energy metabolism and metabolic rate by about 25%. The majority of animals are neutered when they are growing from juveniles to adults. Also, the pet food nutritional statement reported on food labels is for intact dogs and cats, not neutered dogs and cats. The key is to prevent weight gain during this time period, as it is much harder to lose weight that to prevent weight gain. Following neutering it is recommended to decrease caloric intake by 25% and discontinue free-choice feeding.
Food choices and method of feeding influence weight. Today there are a plethora of highly palatable foods and treats available on the market. Despite rising unemployment, credit-card debt and less discretionary spending, American pet owners remain loyal to their animals (and the industry). According to the American Pet Products Association retail sales of pet food were up 4.5% in 2009 at about $18 billion with projected sales to top $21 billion by 2013! Dogs that are allowed to be near their owners at mealtime had a greater tendency to be obese due to the increased likelihood of receiving table scraps. This feeding interaction can become a social problem resulting in over feeding and inappropriate behavior. It has been shown that dogs living in households with health-conscious owners tend not to be obese.
Dogs and cats are subject to the same detrimental affects of obesity as humans with the end result being premature death and earlier onset of obesity-related diseases such as diabetes mellitus, osteoarthritis and some cancers. In a recent study of canine diet and health, dietary calorie restriction was clearly shown to increase longevity in a group of paired sibling Labrador retrievers. The lean-fed dogs were fed 25% less food than their littermate starting at eight weeks of age. The lean-fed dogs lived on average two years longer and had reduced incidence of hip dysplasia, osteoarthritis, and diabetes mellitus.
Reduced activity is a risk factor for obesity in cats and dogs, as well as age. In metropolitan areas apartment dwellers are suggested to be overweight.