Melissa Kelly, PhD, Research Scientist; Nestle Purina Research

Obesity is the #1 concern affecting the general health of the dog.  Purina has developed a 9-point system as a means to evaluate the health of the dog.  The Purina Body Condition System is a validated standard used by veterinarians to evaluate body physique in pets.  Dog owners were requested to score their dogs, followed with a score by the veterinarian.  It was discovered that owners were unable to determine a state of obesity. 

Purina did a Life Span Study over a 14-year period in collaboration with 5 universities.  They found diet restriction influenced quantity of life, quality of life and biomarkers of aging.  With the prevalence of obesity at middle age, disease and immobility sets in.

The Purina Life Span Study evaluated the effects of 25% diet restriction on joint development and subsequent osteoarthritis, several potential markers of aging, and longevity in Labrador Retrievers.  Forty-eight Labrador Retriever puppies from 7 litters of 8 week old puppies were paired by gender and weight and randomly assigned to a control (control) group or restricted (lean-fed) group.  The control group had free access to food for 15 minutes per day, and the lean-fed littermate was fed 25% less food than the control puppy.  At 3.25 years, the formulation and amount fed to both groups of dogs was changed.  The control-fed group was offered 62.1 Kcal of metabolizable energy (ME)/kg of estimated ideal body weight for the rest of their lives.  Each dog in the lean-fed group continued to receive 25% less food than its pair-mate consumed the previous day.  All dogs received the same dry, extruded 100 percent nutritionally complete and balanced diet; 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, they were evaluated annually for body condition using the Purina Body Condition System.  Other health indicators, including annual radiographs, body fat, lean body mass and bone mass, effective glucose and insulin use, serum cholesterol and triglyceride levels, cardiac parameters, immune and antioxidant variables, were measured annually.  Health-related events, as well as time and cause of death, also were recorded.

Earlier results published from this same study showed that hip joint laxity was significantly less among dogs given reduced food intake.  The severity of osteoarthritis (OA) was less in lean-fed dogs as well.  By age 5, moderate-to-severe coxofemoral OA was present in 43% of the control-fed dogs, compared to only 9% among the lean-fed dogs.  By 8 years of age, OA was found in multiple joints (hip, stifle, shoulder, elbow) with greater frequency and severity among the control-fed dogs.  Osteoarthritis was identified radiographically in two (45%) or three (32%) different joints in 77% of the control-fed dogs but only 10% of the lean-fed dogs, at 8 years of age.  Another indicator reflecting the delayed development of OA in the lean-fed dogs is the age at which 50% of the dogs (the median) in each group required regular medical treatment for OA.  Among the control-fed dogs, this occurred at 10.3 years of age, but was delayed by almost 3 years (13.3 years of age) in the lean-fed group, a statistically (P<0.0001) and clinically significant difference.  The need for treatment of any health condition was also delayed in the lean-fed dogs.  The age when 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.  Between the two groups, age at mortality differed more significantly than causes.  Medium life span was increased by 1.8 years, or 15 percent, in the lean-fed dogs compared to the control-fed (P<0.001).  Median life span (age at which 50 percent of the dogs in the group had died) was 11.2 years in the control-fed group compared to 13.0 years in the lean-fed group.  By age 10, only three lean-fed dogs had died, compared to seven control-fed dogs.  At the end of the twelfth year, 11 lean-fed dogs were alive, with only one control-fed dog surviving.  Twenty-five percent of the lean-fed group survived to 13.5 years, while none of the dogs from the control-fed group lived to that age.  Throughout the study, the lean-fed group had a significantly (P<0.01) greater mean percentage of lean body mass.  The lean-fed group also experienced a two-year delay in loss of lean body mass (the average onset of decline was 11 years vs. 9 years) compared to control-fed dogs, and maintained significantly (P<0.01) lower body condition scores.  The average BCS (from age 6 through 12 years) for the lean-fed and control-fed dogs was 4.6 + 0.2 and 6.7 + 0.2, respectively.  Thus, the control fed dogs were only slightly to moderately overweight and the lean-fed dogs were well within the ideal body condition of 4 to 5 on Nestle Purina’s 9-point scale.  Despite this, the correlation between BCS at middle age and longevity was impressive.  Dogs with a BCS of 5 or less at middle age (6 through 8 years of age) were more likely to live beyond 12 years of age compared to those with a higher BCS.  The lean-fed group had lower serum triglycerides and triiodothyronine, as well as improved insulin and glucose utilization.  The Purina Life Span Study demonstrated that feeding to ideal body condition (BCS of 4 to 5 on 9-point scale) increased the median life span and delayed the onset of signs of chronic disease in this group of Labrador Retrievers.

In summary, the study showed that the lean-fed dogs maintained a significantly leaner body condition from 6 to 12 years of age than the control group dogs, with mean body condition scores between 4-5 (ideal) and 6-7 (overfed), respectively.  On average, the lean-fed group weighed less, had lower body fat, and after a certain age, experienced a 2-year delay in the loss of lean body mass as they aged, compared to the control group dogs.  In addition, according to observations of the researchers, the control dogs exhibited more visible signs of aging, such as graying muzzles, impaired gaits and reduced activity, at an earlier age than the lean-fed dogs.

The study provides some insight to human health as well:

“This study is significant for human as well as canine health because it’s the first study completed in a larger mammal that proves the significant power that diet restriction wields in extending life and delaying the markers of aging,” says Dr. Richard Weindruch, University of Wisconsin professor of medicine and expert in the diet restriction field.  “From this study, we can extrapolate that large mammals, including humans, can potentially live healthier and longer through diet restriction.”