Research spanning more than 60 years using rodents and various invertebrate species has shown that the only nutritional intervention that consistently extends life span is food restriction. This 12-year study evaluated the effects of a 25% dietary restriction on the life span and markers of aging in dogs. Labrador retrievers (48 puppies) were paired; one dog was fed 25% less than its free-choice counterpart from 8 weeks of age until death. Food type was age-appropriate for all dogs. Serum biochemical analyses were performed, body condition was scored, and dogs were monitored daily for signs of illness and abnormalities. Compared with control dogs, food-restricted dogs weighed less and had less body fat and lower concentrations of serum triglycerides, triiodothyronine, insulin, and glucose. Age at onset of chronic disease and median and maximum life spans were evaluated. After 9 years of age, bone mass remained constant in food-restricted dogs but had significantly decreased in control dogs. Ranges for the first treatment for osteoarthritis, the most commonly diagnosed chronic disease in these dogs, were 6.8 to 12.9 years in control dogs and 7.9 to 14.1 years in food-restricted dogs. Because median life span was increased and signs of chronic disease were delayed in the food-restricted dogs, restricted feeding and a body condition score less than 5 was recommended.

COMMENTARY: Animals fed less than free choice lived an average of 2 or more years longer and had delayed need for medication for osteoarthritis. Traditional thinking has been that moderate weights are best; this study seems to indicate that skinny is better.

Effects of diet restriction on life span and age-related changes in dogs. Kealy RD, Lawler DF, Ballam JM, et al. JAVMA 220:1315-1320, 2002.