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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

It's Official: Size Matters

It has long been known in human weight research that the size of food bowls, plates, and utensils influence the amount of food served and consumed. These effects are believed to be the result of two famous psychological concepts, the Delboeuf optical illusion and the Ebbinghaus-Titchener size-contrast illusion. It is the logic behind serving dieters their meals on saucers instead of plates and reducing the size of serving utensils.

Research with dog owners has suggested that the size of food bowls and food scooping devices might be a significant contributor to the pet obesity problem. A recent study confirmed that, indeed, the size of food bowls and serving utensils influence the meal size owners feed to their pets.

The Study

Fifty-four dogs and their owners were randomly chosen for the study. Each owner with his or her dog visited the research facility four times for normal feedings of kibbled dog food — using four different feeding utensil combinations. Owners fed with a small scoop and small bowl, a large scoop and small bowl, a small scoop and large bowl and a large scoop and large bowl. No combination was used more than one time for each pet owner.

Statistical analysis confirmed that meal sizes were consistently smaller when owners used a small scoop and small bowl, and consistently larger when the large scoop and large bowl were used. Food amounts did not vary significantly between the large scoop/small bowl and the small scoop/ large bowl treatments. The researchers concluded that the same optical and size-contrast illusions that affect our own portion control are at play when we feed our pets.

Pet Store Behavior

The study seems obvious and common sense would conclude it probably wasn’t necessary. But apparently this concept isn’t that obvious. When I question pet owners about food bowl size or watch shoppers at pet stores, I encounter a consistent behavior: Owners always choose a food bowl much larger than necessary for the size of their pet, with large breeds given enormous containers. A correctly portioned meal looks miniscule (those optical and size-contrast illusions) in a large bowl and hence the tendency to "top off."

Since so few owners use a "true" measuring cup as a scoop (I have never seen feeding instructions on a bag that used the word scoop instead of "8 oz. measuring cup"), our pets are consistently receiving more food than they need. I won’t even get into the calories from treats. Interestingly, the same owners purchase or use a much smaller water bowl than food bowl. Water, the most important nutrient, gets the smallest container! Again, this is just another psychological indicator of our fixation on food.

The Solution

As I have mentioned in other blogs, the food bowl should only be as large as necessary for a pet’s snout to comfortably lick or grab the food. No dog, not even a Mastiff, needs a 9 inch diameter food bowl. Chihuahuas, toy poodles, and cats need little more than a food bowl the size of a tiny dessert parfait cup. And the water bowl should dwarf the food bowl by 2-4 times.

An 8 oz. measuring cup should be the only utensil used as a scoop. Weighing the meal on a kitchen gram scale would even be more accurate and give more consistent meal sizes.

And always remember to follow feeding instructions of the new food when you change pet foods. Foods vary enough in calorie content that feeding a new food in the same amount as the old could be adding too many calories to your pet’s diet.

Dr. Ken Tudor

Image: Graça Victoria / via Shutterstock

Comments  8

Leave Comment
  • Bowl Size
    07/12/2012 10:17am

    "cats need little more than a food bowl the size of a tiny dessert parfait cup"

    Some cats don't like their whiskers to touch the sides of a bowl. I have a couple that wouldn't eat or drink from something that small.


  • 07/12/2012 01:06pm

    Maybe for your sensitive cat, use a plate, but a tiny plate where the proper amount of food completely fills it .. maybe from a child's toy tea set?

  • 07/12/2012 02:23pm

    Or a tea cup plate.

  • Bowl Size
    07/12/2012 01:33pm

    I agree about the size of a cat's food bowl--a few will dig into anything, but many will not put their muzzle into anything once it starts to push their whiskers back. I've regularly seen people put food in straight-sided dishes or custard cups and wonder why the cat doesn't finish their food.

    I have found small relatively flat dessert dishes work best, the sort we used to call "monkey bowls" in the college cafeteria, or even the tiny plates mentioned above from a child's tea set.

    For water I have a fountain but also a bowl or two in each room, and keep them filled to within 1/4" of the top so they don't need to dip too far.

    I'm careful about the finish too--I love vintage things but no vintage ceramics for my cats. I use tempered glass or stainless.

  • Bowl size
    07/12/2012 09:51pm

    I've always used a measuring cup when feeding my cats, and both are of a good weight and size. My vet is always telling me they are at their best weight. On the other hand my Mother free feeds her cats and both are extremely over weight. One more than the other since she chases the other one away from her bowl and eats all of hers too. I try to explain to my Mom that she's just hurting her girls the way she feed them, but I get the line, but they just love to eat and I can't deny them all that they want. So the battle of the bugle goes on in her household, while I have to active and healthy cats. One age 11 and one age 15 months.

  • Scale and cups
    07/13/2012 12:22am

    I've always used a kitchen scale (in grams) and measuring cups and spoons for my dogs and cats. When people see me doing that, they think I must have obsessive compulsive disorder!

    They can think what they want! I'll continue with my scale and cups!

  • Martha Stewart bowl
    07/13/2012 03:13am

    At the recommendation of my vet, I recently purchased the Martha Stewart "obstacle" bowl to help my dog slow down in eating because I was always worried she inhales her food like she's starving. She also gained a little weight.

    Seems to help and now I use measuring cup.

  • Everybody
    07/13/2012 03:21am

    Thank you for your great comments. I am not insensitive to the whisker sensitivity of our feline babies. But if they need a plate then 3Dogs1Cat is right. You have to weigh the food on a kitchen scale. Otherwise you will be victim to the same optical illusions that occurs with food bowls. Plates are extremely, no matter how small, subject to an overfeeding tendency.
    Dr. T

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