Super Size Me?
By Deborah S. Greco, DVM, PhD, Diplomate ACVIM

It is estimated that more than 100 million Americans are overweight and that 25% to 45% of our pets are overweight.  So the question is why?  Is it lack of exercise, consumption of fast food or diets high in fat or carbohydrates?  A recent film documentary, Super Size Me, chronicles the journey of a healthy 185-pound; 6-foot, 2-inch man who embarks on a fast-food odyssey of epic (or super-sized) proportions.  Protagonist Morgan Spurlock consumes all his meals at McDonald's for one month, despite protests from his girlfriend (a vegan), his doctors, and, yes, even his stomach (he begins vomiting out the window of his car soon after instituting "le diet").  Unfortunately his body and health are on the losing end of this project as he gains weight, his liver becomes toxic, his cholesterol increases, his libido sags, and he becomes depressed.  Aptly, he describes the unique combination of hunger and revulsion that is all too familiar to those of us who have eaten bite after bite of calorie-laden, nutrient-poor fast food (i.e., the Big Mac Super Size meal).   And yet we go back for more.  Maybe we overeat because we have to, because we are not getting the nutrients our bodies crave!

FAT CATS
Clearly fast food isn't the cause of feline obesity---or is it?  What is the equivalent of a kitty Big Mac?  Could it be the tower of dry cat food lurking in the corner?  It's convenient (like fast food), it's full of carbohydrates (like fast food), and it's available 24 hours a day (like fast food).  In the wild, cats maintain normal to low bodyweight because they do not overfeed: the body composition of a mouse is approximately 45% to 50% protein, 3% to 5% carbohydrates and 40% to 45% fat---in other words, low in carbohydrates, high in protein.  One of the theories behind feline obesity is that some feline diets are relatively deficient in protein and therefore cats overeat when fed ad libitum in an effort to maintain adequate protein homeostasis.

Why be concerned about obesity in our cats?  Like human beings, obese cats are over 4 times more likely than those of optimal weight to become diabetic, arthritic, and have nonallergenic skin disease.  Cats that are especially at risk for becoming obese are indoor, neutered, middle-aged cats.  Indoor cats tend to do very little in the way of physical activity and there is not much a cat owner can do to make them exercise.  High-protein, low carbohydrate diets (less than 10% on a dry matter basis) allow the cat to self-regulate food intake.  My advice is to feed canned food only as dry foods tend to be higher in carbohydrates; they will love you for it and it will help keep the weight off.

OBESITY IN DOGS
Obesity in dogs may also be a consequence of overeating to obtain optimal nutrients in the diet, but social factors may also play a role.  More often, dog owners are simply unaware of the number of calories in dog snacks and overfeed out of ignorance.  An average-sized 40- pound dog should be eating about 1200 kcal (3 cups of dry food) per day.  If the owner divides that amount and puts the food down twice daily, the dog summarily eats it.  However, if the dog also gets 3 treats per day (200 kcal/treat) or the owner is feeding a "rounded" cup as opposed to a "level" cup of food, the extra calories add up to 4200 per week for the treats and 600 per week for the kibble (calculated based on 3 cups of extra food).  If the dog is sedentary and walked only once a day, those calories will soon translate to extra pounds.  Once clients understand the math behind overfeeding, they can prevent obesity in their dogs by feeding less maintenance food and supplementing treats or by eliminating treats altogether (not likely).

The next time I drive through the neighborhood fast food joint, I'll try ordering the child's meal or maybe just a salad.  In other words, instead of yelling "Super size it" maybe I'll simply say, "No thanks; I'm full"!

Deborah Greco, Advisory Board

August 2004....NAVC Clinician's Brief