I just finished listening to a podcast produced by the Public Radio show Science Friday called “Fallacies of Fat.” In it, Dr. Robert Lustig talks about diet, exercise, weight loss, and health and how they are not all related in the ways that you might think.
Dr. Lustig is a medical doctor, not a veterinarian, but I think some of his points could have important implications when it comes to the well being of dogs and cats. I’m going to talk about obesity and dogs here. For my take on diabetes and cats, head on over to today’s feline version of Nutrition Nuggets.
According to the Association of Pet Obesity Prevention, an estimated 36.7 million dogs (52.5% of the 70 million U.S. pet dogs) are overweight or obese. I can think of no other health condition that has such a profound negative effect on the health of so many dogs. Dr. Lustig takes issue with the common recommendation to exercise in order to lose weight, citing the following facts:
- The largest percentage of calories that a person burns during the course of a day occurs while he or she is sleeping and watching TV. (I suspect that since dogs’ lifestyles tend to mirror their owners’, the same is true for the canine companion curled up on the couch next to us.)
- There is not one study demonstrating that exercise alone will result in significant weight loss.
It basically comes down to math. To lose a pound of fat, we need to burn about 3,500 calories more than we absorb. According to the Mayo Clinic, a 160 pound person would have to walk briskly for more than 11 hours over their normal activity level to burn 3,500 calories, while cutting just 500 calories from their daily intake has the same effect in just one week. 500 calories equates to a single large McDonald’s fries, or a cup or two of most ice creams. Neither option is easy, but cutting 500 calories a day is doable for many people; walking for an additional hour and a half every day (or the equivalent for more vigorous forms of exercise) is not. Now, the situation isn’t exactly the same for dogs, but the general idea that it takes a lot of exercise to equate to a relatively small reduction in calories holds.
This is not to say that exercise is not beneficial. As Dr. Lustig says, it is pretty much the best antidote for anything that ails you. I’d say the same is true for dogs. Exercise can help with musculoskeletal problems, behavioral issues, and so much more. Doctors and veterinarians simply need to stop touting it as being effective for weight loss and start emphasizing its health benefits instead.
When a dog needs to lose weight, veterinarians and owners should focus almost exclusively on cutting calories. Any weight loss that is attributable to an increase in exercise should be seen as the icing on top of the cake. (Sorry, bad analogy for this subject matter.)
Dr. Jennifer Coates