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Why Your Dog is Fat: New Nutrition Study

Why your dog is fat

When you see a fat dog, you probably think the dog is overweight because the owner feeds it too much. While that is likely part of the reason, a new nutrition study explains there is an additional reason why your dog is fat--and hopefully the information will help dog parents take better care of their canine companions.

Too many dogs are fat

Before presenting the results of the new international study, a few pieces of information from the Association for Pet Obesity Prevention (APOP) can set the stage. Approximately 53 percent of dogs in the United States are overweight or obese, according to a recent survey by the APOP. That means dogs are not far behind the number of people in the US who are carrying an excessive amount of weight.

Domesticated dogs depend on their owners (pet parents) to make sure they are properly fed and maintained at a healthy weight, but the high percentage of fat dogs suggests this is not happening. In fact, one problem is that many pet owners are not aware their dog is too fat.

As APOP founder Dr. Ernie Ward explained, "the most distressing findings in this year's study was the fact that more pet owners are unaware their pet is overweight." More specifically, the survey found that 22 percent of dog pet parents said their dog was of normal weight when it was really overweight or obese.

That brings us to the new study, which was conducted by the Waltham® Centre for Pet Nutrition, along with scientists from the University of Sydney, Australia, and the Institute of Natural Sciences at Massey University in New Zealand. This team evaluated the natural feeding behavior of adult domestic dogs, using five breeds as examples: papillons, miniature schnauzers, cocker spaniels, Labrador retrievers, and St. Bernards.

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The scientists wanted to determine if domestic dogs regulate their intake of macronutrients because, as they noted in the introduction, "A fundamental, but little-researched, area in the evolution of nutritional regulatory strategies concerns the impacts of domestication and the associated selection pressures on the preferred dietary macronutrients profiles of animals."

The study involved three highly controlled experiments during which the dogs were offered either dry or wet foods that consisted of varying levels of protein, carbohydrates, and fat. Analysis of all the observations yielded the following:

  • When the dogs were given a choice, they consistently regulated their consumption of protein, fat, and carbohydrates, and the proportions equaled about 30% protein, 63% fat, and 7% carbohydrates
  • Some dogs will eat too much--more than twice as many calories as they need--when they are provided with excess food

The importance of this study
According to the study's lead author, Adrian Hewson-Hughes, of the Waltham Centre for Pet Nutrition, "The finding that domestic dogs will naturally seek a dietary intake that is high in fat and that they will readily overeat if given the opportunity probably reflects the feeding behaviour of their wild ancestors."

However, domesticated dogs do not have to hunt for their food, and do not experience the continuous possibility of feast-or-famine that wild dogs and wolves do, which is the reason the latter tend to eat excessively when they do make a kill. Many domesticated dogs also do not get the amount of physical exercise that their wild counterparts do.

As Hewson-Hughes pointed out, this study "reinforces the importance of responsible feeding measures, such as portion control, for helping ensure dogs maintain a healthy body weight." Therefore, if your dog is too fat, the reason may be a combination of feeding him or her too much, plus the natural tendency for dogs to "maximise their calorie intake whenever possible," according to Hewson-Hughes.

Association for Pet Obesity Prevention
Hewson-Hughes AK et al. Geometric analysis of macronutrient selection in breeds of the domestic dogs, Canis lupus familiaris. Behavioral Ecology 2012; doi:10.1093/beheco/ars168

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