Tipping the scales at 97 pounds, Sam was a chubby black Labrador retriever. Partial to meat, potatoes and the occasional mouthful of popcorn, he was a fine dinner companion and not very old when walking became difficult because of excessive weight. Today, Sam is a trim 85 pounds, much closer to the recommended weight range for his breed. His owner did it the old-fashioned way -- guessing what might be the right amount of food to feed for healthy weight loss.

Now, an iPhone app, developed by Cornell students, takes the guesswork out of achieving a dog or cat's appropriate weight.

CUPetHealth, available for $3.99 from the iTunes store and distributed by the College of Veterinary Medicine at Cornell University, allows caregivers to track what and how much they feed their cats or dogs. After inputting the daily diet and noting several lifestyle variables that must be factored into the calculation to determine the appropriate number of calories each day, the app responds with "overfeeding," "underfeeding" or "appropriate."

Caregivers select food items from a ready-made list (which includes table food) or they can enter additional food items before the app completes the calculation. The app also provides suggested diets with the click of a button. In addition, the app electronically tracks companion animals' vaccinations, including heartworm, notifying the owner when it's time to revaccinate or administer another heartworm pill.

"Nutrition is an ever-growing concern for pets," said Joe Wakshlag, D.V.M. '98, Ph.D. '05, assistant professor at the Vet College. "The Centers for Disease Control says that America has become 'obesogenic,' meaning that we live in a world that promotes increased food intake, unhealthy food choices and reduced physical activity. Our pets live in the same world and are suffering the same consequences of obesity."

The app, which is compatible with the iPhone, iPod Touch and iPad, was developed by seven students enrolled in a computer science class at Cornell who partnered with Wakshlag to ensure the medical accuracy of the application. The students earned credit for the class project and will also share in any revenue generated by sales of the application. The application requires iPhone OS 3.1.3.