NEW YORK (Reuters Health) - Adding to the growing evidence that calorie-counting might make for a longer, healthier life, a study of dogs suggests that cutting down on Fido's treats could tack up to 2 years onto his life.

Researchers found that Labrador retrievers raised on a lower-calorie diet not only lived longer than their more gluttonous litter-mates, but also avoided common canine conditions like osteoarthritis for a longer period of time.

Past research in organisms ranging from yeast to rodents has suggested that calorie restriction aids longevity. The authors of the new study believe this is the first to tie low-cal living to a longer life span in a mammal larger than rodents. Research in rhesus monkeys has already suggested lower-calorie diets can forestall chronic disease.

Scientists at the University of Pennsylvania in Philadelphia, and Nestle Purina Pet Care in St. Louis, Missouri, led the study. The results were published in a recent issue of the Journal of the American Veterinary Medical Association.

In the study, 48 Labs from seven litters were paired off to compare the effects of two diets. One dog in each pair was fed until his heart's content until about age 3, when their diets were reigned in to keep them from becoming obese. The other dog in each pair ate 25% fewer calories than his partner, before and after age 3.

The researchers found that the median life span--the age by which half of the dogs had died--was nearly 2 years longer among the calorie-restricted dogs (13 years, versus 11.2 years). The dieting dogs also tended to go longer without needing treatment for chronic conditions--age 12, on average, compared with age 10. In both groups of animals, osteoarthritis was the most common medical problem, but the calorie-restricted dogs developed the condition an average of 3 years later than their litter-mates.

"Because osteoarthritis is painful, this deferral represents a substantial boost in quality of life," study co-author Dr. Gail K. Smith, of the University of Pennsylvania, said in a statement.

Throughout much of their adult lives, the calorie-restricted dogs also had less body fat and lower levels of certain blood fats, blood sugar and the sugar-regulating hormone insulin. In humans, these traits are associated with a lower risk of major disorders like type 2 diabetes and heart disease.

SOURCE: Journal of the American Veterinary Medical Association 2002;220:1315-1320.

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