WARNING SIGNS

There are pads of fat over the hips and base of the tail, he waddles while walking, he finds it difficult to move or is short of breath.

Even a slight weight gain can be serious for your pet. An extra five pounds on a dog that should weigh 17 pounds or an extra three pounds on a cat that should weigh 10 pounds is equivalent, for example, to an extra 50 pounds on a person who should weigh 170 pounds.

FACTS & TIPS

The new book, "Fitness Unleashed! A Dog and Owners' Guide to Losing Weight and Gaining Health Together," contains these tidbits:

Breeds that are at especially high risk for easy weight gain are Labrador retrievers, Cairn terriers, cocker spaniels, dachshunds, corgis, shelties, basset hounds, beagles and King Charles spaniels.

Spaying or neutering reduces a dog's need for calories by 5 percent.

Healthy snacks for always-hungry dogs could include small amounts of baby carrots, frozen green beans, blueberries, small shredded wheat squares, Cheerios, apple slices or small pieces of flavored rice cakes.

You'll want to consult your vet for advice on brand of food and portion size, but here's a guideline: 40 calories per pound of body weight for small dogs; 30 calories per pound for medium dogs; 20 calories per pound for large dogs. Most dry dog foods contain an average of 350 calories per cup.

MORE ON THE PETFIT CHALLENGE

For details on the Hill's 2006 National PetFit Challenge, go to www.petfit.com. All participating pets must be under the care of a veterinarian.

And one eligibility requirement that might deter you from participating because of the blatant marketing: All competitors must be eating food made by Hill's Pet Nutrition -- either Science Diet Light Adult or Prescription Diet, which is available only from vets. The Web says contestants should expect to pay $150-$225 for dog food and $45-$65 for cat food for the duration of the contest.