The Purina Life Span Study, conducted from 1987 to 2001, represents the first completed canine lifetime restriction study. Findings from the study proved that maintaining dogs in lean body condition extended their media life span by 15 percent or nearly 2 years, for the labrador Retrievers in the study. The study showed several benefits for feeding dogs to ideal body conditions.
“The Purina Life Span Study evaluated the effects of 25-percent diet restriction on body condition and a variety of health parameters, as well as life span,” says Melissa Kelly, Ph.D., Purina Research Scientist. “The study also evaluated the effects of diet restriction on potential markers of aging, such as the age when the dogs began requiring medical treatment for chronic conditions.”
The 14-year study, which took place at the Purina Pet Care Center in Gray Summit, Mo., compared 48 Labrador Retriever dogs from seven litters. The dogs were paired within the litters by gender and weight and randomly assigned to a control group of restricted (lean-fed) group when they were 8-week-old puppies. “The control group had ad libitum access to food for 15 minutes a day, and the lean-fed litter mate was fed 25 percent less food than the control puppy” Kelly says.
All dogs received the same dry, extruded 100 percent nutritionally complete and balanced diets, puppy then adult formulations- just the amount fed to the control-fed and lean-fed groups differed. Dogs were weighed weekly as puppies, periodically as adolescents, and weekly as adults. Beginning at 6 years of age, the dogs were evaluated annually for body condition using the Purina Body Condition System, a validated standard used by veterinarians to evaluate body physique in dogs.
Other health indicators were measured annually. These include annual radiographs, body fat, lean body mass, bone mass, effective glucose and insulin use, serum cholesterol and triglyceride levels, cardiac parameters, immune and antioxidant variables, etc. Health-related events, as well as time and cause of death, were also recorded.
Additionally, the need for treatment of health conditions was delayed in the lean-fed dogs. The age at which 50 percent of the dogs required treatment for a chronic condition was 12.0 years among the lean-fed dogs compared to 9.9 years for the control-fed dogs.
Related to body condition, the lean-fed group had a significantly greater mea percentag3e of lean body mass throughout the study. “The lean-fed group experienced a two-year delay in loss of lean body mass, with the average onset of decline being 11 years vs. 9 years for the control-fed dogs. The lean-fed dogs also maintained significantly lower body condition scores,” Kelly says.
Control-fed dogs were slightly to moderately overweight, and the lean-fed dogs were well within ideal body condition on the Purina Body Condition System (BCS). On the nine-point scale, a body condition score of four or five is considered ideal; 6 through 9 is considered too heavy; and one through three is considered too thin.
Median life span, the age at which 50 percent of the dogs in the he group had died was 11.2 years in the control-fed group compared to 13.0 years in the he lean-fed dogs. Thus, the median life span was increased by 1.8 years or 15 percent in the lean-fed dogs compared to the control-fed dogs. At the end of the 12th year, 11 lean-fed dogs were alive but only one control-fed dog was surviving. Ultimately, 25 percent of the lean-fed group survived to 13.5 years, while none of the control-fed dogs lived to that age.
“The Purina Life Span Study demonstrated that feeding to ideal body condition, which would be a body condition score of four or five on a nine-point scale – proves that lean dogs live longer and healthier lives,” Kelly says.
*2003 National Parent Club Canine Health Conference, taken from Purina’s “Today’s Breeder Publication” Issue 46.