If you think your pets could join you on a New Year’s weight loss plan, consider the harmful and even deadly effect obesity can have on an animal companion. Here are some of the potential consequences:

Joints and bones: “Extra weight aggravates the joints,” says Denver veterinarian Kevin Fitzgerald, of Animal Planet’s “Emergency Vets” and “E-Vet Interns.” “Things like underlying hip dysplasia – if you keep lean, you’re not going to add to it. Dogs that are overweight have a much higher incidence of problems with the knees.” And in animals that already have a tendency toward bad backs, including specific breeds like the dachshund, “you don’t want to put extra weight on those discs that are bad to begin with.”

Heart and respiratory system: “We have a lot of respiratory problems in overweight animals. Things like collapsing trachea and asthma are tremendously aggravated by being overweight,” Fitzgerald says. And the relationship between extra weight and heart disease is well-established in both humans and animals. “The more weight you carry, the harder it is for your heart.”

Diabetes: As in humans, being overweight carries the risk of diabetes. “Your pancreas is set to an optimal body weight. If your body mass is more than it should be, your pancreas is overworked, stops producing insulin, and bang, you’ve got diabetes,” Fitzgerald says.

Cancer: Extra weight can increase cancer risk, and the effects are long-term. “Dogs that are obese at 1 year of age have a higher incident of mammary cancer as 10-year-olds,” Fitzgerald says. And diets high in fat and sugar make your pets more prone to intestinal cancer and cancer of the colon.

Lifespan: If you keep your pets at a healthy weight, you’re likely to have them with you longer. “Some studies with beagles have shown that optimal weight beagles live one to two years longer than dogs that are 20-30 percent overweight,” Fitzgerald says.