What Extra Weight Costs a Dog: The Labrador Lifetime Study
In a lifelong study of 48 Labradors, the leaner dogs lived longer. What it found, what a study of 50,787 pet dogs added, and who paid for both.
Written by thecanineledger
In a study that followed 48 Labrador Retrievers for life, “Median life span was significantly longer for dogs in which food was restricted.” (Kealy et al., Journal of the American Veterinary Medical Association 2002, abstract).
While that’s one of the most quoted findings in dog nutrition, it comes from 48 dogs, in a study run by a pet food company’s researchers. A much larger 2019 study of pet dogs points the same way. This page sets out what each found, and what neither can show.
1. The Labrador study
The design. “Dogs were paired, and 1 dog in each pair was fed 25% less food than its pair-mate from 8 weeks of age until death.”
What it found. “Compared with control dogs, food-restricted dogs weighed less and had lower body fat content”. And “The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs.”
The follow-up. A 2005 paper on the same dogs found that “causes of death were generally similar between the 2 feeding groups.” The leaner dogs died of much the same things, only later (Lawler et al., Journal of the American Veterinary Medical Association 2005, abstract).
Disclosure. The authors’ affiliation was a pet food company’s nutrition research department.
What it doesn’t show. The “food-restricted” dogs weren’t starved. They ate 25% less than dogs fed more freely. The study compares two feeding levels in one breed, not a fat dog with a normal one.
Our note: We read only the abstracts. “Fed more freely” is our wording for the control dogs.
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2. The pet dog study
The design. A 2019 study looked at 50,787 middle-aged neutered pet dogs seen at about 900 vet hospitals in North America (Salt et al., Journal of Veterinary Internal Medicine 2019). It compared dogs that were overweight or normal at 6.5 to 8.5 years old, in 12 breeds.
What it found. “In all breeds, median life span was shorter in overweight compared with normal weight dogs”.
How big the gap was. It varied by breed. The difference was greatest in male Yorkshire Terriers: “overweight: 13.7 years” against “normal: 16.2 years”. The authors say the effect was “least for large‐breed dogs (eg, 5 months)”.
What it doesn’t show. “Given that the study was retrospective and observational, it was not possible to determine the reasons for the association between overweight body condition and life span, and causality cannot necessarily be assumed.”
Disclosure. Three authors worked for a pet food research centre and one for the hospital chain. “Both companies both are owned by” the same parent company.
Our note: Both studies were run by people linked to pet food companies.
→ Breed and Lifespan: What the UK Primary-Care Data Shows
3. What it means for your dog
- A lean dog is the goal. Both studies point the same way, one by experiment and one by observation.
- Middle age matters. The 2019 authors say vets “should consider promoting healthy body condition for dogs, particularly from midlife onward.”
- Don’t cut food on your own. Ask your vet to score your dog’s body condition and set a plan.
Our note: The last point is ours. Cutting food without a plan can be a problem, especially in puppies, so plan it with your vet.
Our note: The 2005 abstract says unplanned weight changes in mid and later life “may indicate the need for thorough clinical evaluation.” See your vet about unexplained weight loss.
4. What we could not verify
| Commonly said | What we found |
|---|---|
| “Lean Labradors lived about two years longer” | Not confirmed here. The abstracts we read say the life span was significantly longer but don’t give the figure. |
| “Being overweight shortens every dog’s life” | In all 12 breeds studied, median life span was shorter. The study can’t prove the weight caused it. |
| “A few extra pounds don’t matter” | Not supported. The 2019 study found shorter median lives in overweight dogs. |
| “These studies are independent” | No. Both were run by people linked to pet food companies. |
Sources
- Salt C, Morris PJ, Wilson D, Lund EM, German AJ. Association between life span and body condition in neutered client-owned dogs. J Vet Intern Med 2019: retrospective case-control study, 50,787 dogs. Authors employed by companies owned by one pet food parent company
- Kealy RD, Lawler DF, Ballam JM, et al. Effects of diet restriction on life span and age-related changes in dogs. J Am Vet Med Assoc 2002. ⚠️ abstract read. Paired feeding study, 48 Labradors. Authors at a pet food company
- Lawler DF, Evans RH, Larson BT, et al. Influence of lifetime food restriction on causes, time, and predictors of death in dogs. J Am Vet Med Assoc 2005. ⚠️ abstract read. Same 48 dogs
Always confirm with your vet before acting on anything on this page.