Animal studies have concluded that restricting the amount the animal eats extends their life span. Diet restriction also appears to delay or mitigate the development of a number of age related diseases.

Effect of diet restriction in dogs

Study design

To test the theory that diet restriction affects a dog’s life span and onset of age related diseases, 48 Labradors from 7 litters were entered into a pair feeding design study.

At 6 weeks of age, dogs were paired by sex and body weight and assigned randomly to one of two feeding groups. Dogs in the first group were fed ad libitum while dogs in the second group were fed 75% of the amount consumed by their mate. Each dog in the pair ate the same food, it was only the quantity that differed.

At 3.25 years, the following two changes were made:

• Firstly, both dogs in the pair were changed from growth to maintenance formula (27% protein to 21% protein content).

• Secondly, the amount of food fed was adjusted. The ideal body weight for each dog was estimated and the dogs in the first group (fed ad libitum) was fed 62.1 Kcal of metabolizable energy / kg of ideal body weight. The other dog in the pair was fed 25% less.

The dogs in the first group were known as the control group while the second group was the restricted feed group.

From 6 years, the following measurements were taken:

• Assessment of body condition on a 9 point scale – 1 emaciated and 9 severely obese.

• Lean body mass

• Body fat mass

• Bone mass

• Serum concentrations of glucose, cholesterol and triglycerides.

Results

Life span

The median life span of the control group dogs was 11.2 years. (Calculated as the age when 50% of the dogs in a group were deceased.) While the median life span of the restricted feed group was 13.0 years. Maximum life span (when 90% of dogs in a group were deceased) was 12.9 years for the control group and 14 years for the restricted feed group.

Body condition

Body weight on average was 26% lower in the restricted feed group throughout the study.

Lean body mass

Lean body mass decreased in the controlled feed group after 9 years but a decreased was not detected in the restricted feed group until after 11 years. While dogs in both groups showed a decrease in lean body mass from 6 – 12 years, the restricted feed group had a greater mean percentage of lean body mass.

Body fat mass

Percentage of body fat mass was significantly higher in the control fed group than the restricted group throughout the study.

Bone mass

Bone mass in the controlled fed group decreased after 9 years whereas the bone mass in the restricted feed group remained constant.

Serum levels

Mean serum triglycerides and glucose concentrations and fasted plasma insulin levels in the restricted fed dogs was significantly lower than the control group.

Onset of age related diseases

The following chronic diseases were diagnosed in the dogs as they aged:

• Osteoarthritis

• Malignant neoplasia

• Benign neoplasia

• Recurring skin disease

• Hepatic disease

• Cystic endometrial hyperplasia

• Pyometra

• Hypothyroidism

• Seizures

Of the dogs that developed osteoarthritis, the age range at which dogs in the control fed group required treatment was 6.8 – 12.9 years while dogs in the restricted feed group did not require treatment until 7.9 – 14.1 years.

The age at which dogs required treatment for one or more chronic conditions in the control feed group was 4.6 – 12.9 years compared to 4 – 14.1 years for the restricted feed group. The mean age of survival without treatment for a chronic condition in the control group was 9.9 years compared with 12 years for the restricted feeding group.

Conclusions

This study drew the following conclusions:

• Restricting diet intake significantly increased median life span.

• Restricting diet also increased the median age at which dogs required treatment for osteoarthritis and other age related chronic conditions.

This study observed a correlation between longevity and excessive fat deposits in animals in which diet was not restricted. In studies of rodents, even obese rats that had restricted feed regime lived longer which indicates a correlation between longevity and food consumption.

In this study the body fat of restricted fed dogs was 12 – 20% and their body condition score 4 – 5. Links between high body fat content and onset of and severity of chronic conditions. In studies of primates, lower morbidity rates in animals with body fat 10 – 22%.

Takeaway message for dog owners

This study made a recommendation that to increase dog’s life span and prevent early onset of age related diseases, dogs’ diet need to be restricted so they maintain a body condition score less than 5.

How do you keep your dog lean and healthy? Leave me a comment with your tips and hints.

Until next time, enjoy your dogs.

Source:

D Kealy, Richard & Lawler, Dennis & Ballam, Joan & L Mantz, Sandra & N Biery, Darryl & Greeley, Elizabeth & Lust, George & Segre, Mariangela & Smith, Gail & D Stowe, Howard. (2002). Effects of diet restriction on life span and age-related changes in dogs. Journal of the American Veterinary Medical Association. 220. 1315-20.