A 14-year study of dog diets and health has found that those on a reduced-calorie diet live a median of 1.8 years longer than those on a regular diet. The dieting dogs also had slower onset of chronic diseases such as osteoarthritis.

The study, carried out by scientists from a number of institutions, including the Nestle Purine PetCare Company, is the first on caloric restriction’s impact on large mammals to be completed. Similar studies on nonhuman primates are in process.

Forty-eight Labrador retrievers from seven litters participated in the study. The researchers paired littermates at eight weeks and fed one 25% fewer calories than the other.

Dogs with reduced food intake had a median lifespan of 13 years, while the control group had a median lifespan of 11.2 years.

And long life wasn’t the only benefit. “Impressive as they are, the life span figures are only part of the story,” says Gail K. Smith, a professor at the University of Pennsylvania School of Veterinary Medicine. “The study also showed that lean body conformation forestalls some chronic illnesses, most notably osteoarthritis, and that diet can either mitigate or exacerbate the expression of genetic diseases.”

Osteoarthritis — a condition that often affects large dogs — is a good example. At age two, only one of the 24 calorically-restricted dogs had osteoarthritis in the hips, compared to six in the control group. By age 10, six in the former group had osteoarthritis compared to 19 in the latter.

“Dogs in the calorie-restricted group didn’t require treatment for osteoarthritis until a mean age of 13.3 years, fully three years later than the dogs in the control group,” Smith says. “Because osteoarthritis is painful, this deferral represents a substantial boost in quality of life.”