But even a luxury spa environment can't mask the hard work of working out. For Abbe, a 6-year-old yellow Labrador retriever who is about 20 pounds overweight, a short tussle with a toy leaves her panting. She does better retrieving a ball from an indoor pool, a task that continues to engage her after three dozen tosses. "The will is so there," said Lisa Tims, her trainer at the Morris Animal Inn, as Abbe swam to get the ball before lumbering out of the water.
Cesar Millan, the popular dog trainer whose books and television shows promote a philosophy of "exercise, discipline, affection," said most dogs were overweight because of lazy owners who confuse food with affection and attention. Letting the dogs out in the backyard is no substitute for a walk, he added. And giving the dog a cookie doesn't make up for not playing with him.
"Dogs today have butlers and maids," Mr. Millan said. "They don't hunt for their food anymore, but they should work for food." And that work needs to include walks during which the dog is focused on obeying commands to be physically and mentally engaged.
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For the last seven years, the University of Tennessee College of Veterinary Medicine has offered a fat camp for dogs, inpatient and outpatient. But the dogs who live at the clinic tend to be more successful, said Dr. Angela Witzel, a veterinarian at the university who specializes in animal nutrition. "A dog can give me big puppy-dog eyes, and I'm still not going to give him a piece of chicken," Dr. Witzel said, whereas an owner may not be able to resist the appeal.
In choosing dog food, she recommended checking the label on store-bought food for the endorsement of the Association of American Feed Control Officials, an organization that helps develops nutritional standards for animal food.
And "if you are going to use a homemade dog food, consult a veterinarian," Dr. Witzel said, because different dogs have different nutritional needs. "For instance, a dog doesn't need carbohydrates unless she is pregnant or lactating."
Lisa Walsh, the owner of Loyalville, a kennel and training center in Hatchbend, Fla., estimated that two-thirds of her canine clients were overweight when they arrived. She cited inactivity and foods high in carbohydrates as causes. To solve the problem, Ms. Walsh offers one-on-one, 24-hour care and training at $1,250 a month.
She advocates a diet that includes what she called "the prey model" of raw, meaty bones and organs. "It's going to gross some people out," she said, "but the ideal meal would be a whole rabbit. Or a whole squirrel for a fox terrier." (For squeamish owners, Ms. Walsh recommended serving dogs dehydrated or frozen raw-food diets; raw chicken is another option.)
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Indigo Ranch in Vernonia, Ore., is a kennel that offers what it calls a doggy fat camp. The camp began about two years ago, shortly after a county shelter contacted Indigo Rescue, the nonprofit rescue organization financed by Indigo Ranch, about a 3-year-old Lab aptly named Butters. At 142 pounds, he was considered unadoptable and was about to be euthanized, said Heather Hines, the director of Indigo Ranch.
"He was a friendly, wonderful dog, but he was huge, his coat was greasy, and he had to lie down to eat his food," Ms. Hines said. She focused on his diet first because, as she explained, "he couldn't stand up for long."
Once Butters started losing weight, Ms. Hines began increasing his activity. About five months after he arrived, he had slimmed to 84 pounds.
The newly trim Butters discovered he had a knack for catching a ball in midair, said Paige Reed, whose family adopted him in 2011. "He didn't know he could run or jump until he lost the weight," Ms. Reed said. "Now he's athletic, loves playing with us and with other dogs."
Ms. Hines, who has seen all manner of excesses in her line of work, said: "People think it's funny or cute when their dog is fat. One woman told me she saw her husband feeding Häagen-Dazs leftovers to her dog."
Bad diets like that are responsible for 60 to 70 percent of weight gain in dogs, said Dr. Ernie Ward, a veterinarian in Calabash, N.C., who founded the Association for Pet Obesity Prevention and is the author of the 2010 book "Chow Hounds: Why Our Dogs Are Getting Fatter." Instead of ice cream, Dr. Ward recommended feeding your dog more of what you might eat if you were on a diet: vegetables like carrots, broccoli, asparagus and green peas.
"This is a human problem," he said. "No pet is making a sandwich and eating a bowl of ice cream at midnight."
Fat Dog Slim
Put down the bag of treats and get off the sofa: the same advice that is good for you is good for your dog, say those who treat obesity in pets. Besides common-sense wisdom about eating less and moving more, there are a number of strategies and practices to slim down dogs or keep them from gaining weight. But before starting a new diet and fitness program, a checkup is important, said Deborah E. Linder, a research assistant professor at the Tufts Cummings School of Veterinary Medicine and head of its Obesity Clinic for Animals. Weight gain in a dog may be a symptom of a disease or an underlying problem like a low thyroid level.
Once you have the go-ahead, begin with what experts call a touch test: run your hand over your dog's ribs; the area should feel no more padded than the back of your hand, Dr. Linder said. Then weigh your pet. If your dog is small, use a baby scale or weigh yourself and your dog together, and do some subtraction. For larger breeds, ask to use your veterinarian's scale.
Exercise is vital to a pet and to any weight-loss program, said Cesar Millan, the dog trainer. Basically, anything "that makes a dog a dog is good exercise," Mr. Millan said. That means walking, running, swimming, herding, jumping in agility training, search-and-rescue work. The optimal amount and intensity of exercise depends on the age, breed and health of the dog; some are so overweight that short walks are the only option. And shorten exercise and increase access to water in hot weather.
Find out from your veterinarian how many calories your dog should consume every day and then contact the manufacturer of your dog food to determine its calorie content. An active adult Lab, for example, may consume 1,000 calories a day, Dr. Linder said, but no more than 10 percent of it should be treats. And some chew treats, she added, are 1,000 calories. Aim for a safe rate of weight loss, generally 1 to 2 percent of a dog's body weight per week. (The American College of Veterinary Nutrition has more advice and a list of certified nutritionists at acvn.org.)
And don't let pets appeal to your guilt to get you into overfeeding them. Dr. Linder suggested hiding some of your dog's daily food in toys, so nosing, poking or prodding is required to obtain it. She added, "Making them find some of their food exercises their mind and body."