I asked the advice of Dr. Jennifer J. Brinson, veterinarian and researcher on obesity in pets at the University of Illinois Veterinary Medicine Teaching Hospital in Urbana. For example, pets of any body condition can get diabetes, but the disease is more difficult to manage in obese pets because the additional body fat interferes with insulin effectiveness. Problems such as torn ligaments are more common in obese pets both because of their disproportionate size and because they often don't have the muscle tone to balance and support the extra weight. Arthritis is not caused by obesity but maybe worsened by the extra load on the arthritic joints. Just about every organ in the body maybe affected by obesity, but most at risk are the musculoskeletal, cardiovascular, and respiratory systems.
Obesity also compromises the effectiveness of a proper physical exam.
Heart and lung sounds can be masked by body fat. This may prevent the veterinarian from finding early indicators of disease and delay diagnosis until a disease has reached advanced stages. There are diseases, such as hypothyroidism and Cushing's disease, that are associated with weight gain. Excess weight is easier to prevent than to lose. The more weight there is to carry around, the more inactive a pet becomes, and the harder it is to exercise and reduce weight.