For Bella Walters, Thanksgiving begins the season of culinary splurge. From now until New Year’s Day, she eats what she wants, no matter the normal rules. Thursday will feature her favorites: turkey and dressing, collard greens and sweet potato pie.  The problem comes in January, when five-year-old Bella must learn how to eat dog food again.  Steven Walters, her owner, blames his uncles for feeding Bella, a Bichon Frise and poodle mix, human food. But he admits he’s part of the problem. “I just feel like everybody else is indulging, why can’t Bella?” says Mr. Walters, a school counselor and actor from Queens, N.Y.  As pets enjoy new status in the social pecking order (think dogs with more Instagram followers than you), Thanksgiving has become the ultimate time for people to pamper their four-legged friends. But with pet obesity rates on the rise, more folks are also grappling with how to share the holidays without making Fido fat, sick or simply more partial to human food.  Experts warn that certain delectables are truly harmful for dogs and cats, and cite anecdotal evidence that visits to animal hospitals spike around this time of year.  “Everybody seems to take a break from healthy habits during the holidays,” says Ernie Ward, a Calabash, N.C., veterinarian who is also founder and president of the Association for Pet Obesity Prevention. He says people don’t realize that a piece of cake is a lot of food for a small animal, and that fatty foods, bones, breads, chocolate and sugar are particularly risky.  “Before you know it, Uncle Bob has given your dog half a pie,” he says.  His group did a study and found that both dogs and cats gained weight over the holiday season. He and other animal-health types suggest that families treat their pets to lean turkey, green beans, sweet potatoes or pumpkin. (Sorry Rover: that’s pumpkin, not pumpkin pie.)  More than half of all dogs and cats are overweight, Mr. Ward’s research finds, yet owners don’t always realize it.  Writer Susan Orlean recalls how her veterinarian once asked if she wanted to bring her Irish setter, Molly, onto a television show. Ms. Orlean agreed—figuring Molly’s beauty and smarts made her the perfect guest.  It wasn’t until the show was under way that Ms. Orlean heard a teaser for her segment: pet obesity. She had figured Molly, now deceased, was “a little chubby” but not so corpulent. She guesses Molly was about 90 pounds at the time.  “I’m sitting in the audience ready to die,” she recalls.  Ms. Orlean—who has written a biography of Rin Tin Tin, co-authored a cookbook for dogs and penned articles about lions, tigers, mules and other critters—says she never gives her pets human dishes, mostly because she doesn’t want them begging at the table. Still, she understands why others succumb.  “When they look at you and you’re eating, say, a giant cheeseburger and you’ve given them a miserable bowl of kibble and they’re looking at you with remarkable pathos and sadness, you go, oh my God, I’m so mean, I’m not feeding my dog,” she says. “And they are so incredibly happy when you do.”  The dog-obesity epidemic has spurred its own thriving cottage industry. There are canine diet consultants, personal weight loss coaches, doggy fat camps, canine fitness boot camps and websites that celebrate the biggest losers. Dog fitness products monitor activity with GPS precision and plastic surgery can remove sagging skin after weight loss.  “Did your dog pack on a few pounds over the holidays?” asks the website for one fitness camp.  There are limits to what owners will do. A canine weight-loss drug called Slentrol was brought to market in 2007. It was discontinued last year due to sluggish demand, according to manufacturer Zoetis Inc. ZTS 0.09 %  As with humans, diet and exercise do work, experts and owners say.  When Kale Chips, a beagle, was rescued from a Chicago animal shelter, he weighed 85 pounds and couldn’t walk. He was placed with a foster family in nearby Downers Grove, Ill., and over the course of nine months of diet and exercise, he lost 40 pounds. His weight loss has been chronicled via his own Instagram account, @kalechipsthedog, which has more than 2,100 followers.  The key was reducing his intake to what a dog his size should eat. In his case, he needs about 1,100 calories a day, says Beth Staley, the owner of Happy Dog Barkery, a pet specialty store and bakery, who is fostering Kale.  He’s worked so hard, she says, that he’ll get a Thanksgiving treat—a turkey-shaped dog cake made of pumpkin or peanut butter, with a cream cheese and honey frosting.  For other owners of weight-challenged pets, Thanksgiving can be a hairy time.  Pam Begelman’s adopted pug, Captain Morgan, has lost about five pounds since May and she is considering giving him some people-food at dinner. She says her husband is known to slip him bits of steak under the table.  “I just came from the store with diet dog food. It’s a big dilemma,” says Ms. Begelman, a retired retail employee in Delray Beach, Fla.  Other owners may know there is a problem but just can’t bring themselves to turn tail with diet and exercise.  Max Fisher of Washington, D.C., says he realized that Indiana Jones, his four-year-old orange tabby cat, was gaining weight when he heard chairs crashing in the middle of the night because the feline was toppling them over when he jumped on them. Still, it is hard to claw back the food.  “The only thing he has ever not eaten was diet cat food. He’ll eat refuse out of the trash, off the floor, but he just went on a little kitty strike,” Mr. Fisher says, adding that Indiana has many techniques to get what he wants.  “He’ll get on the counter and swat my guests on the back of the head if he’s hungry,” says Mr. Fisher. “There’s this little terrorist running around my apartment and I’ve been completely cowed.”  As with children, dogs aren’t always interested in making healthy choices. Bill Portlock, a marine biologist from Sparta, Va., typically doesn’t feed his Labrador retriever human food. But one Thanksgiving, nobody really liked the Brussels sprouts so he put some leftovers into seven-year-old Annie’s bowl.  “She proceeded to lick the cheese sauce off and left (all) five Brussels sprouts,” he recalls.  At the Walters’ home in Queens, the biggest problem is getting Bella to go back to dog food after the holidays. The family mixes her dog food with turkey gravy and slowly tapers down until she’s back on her normal diet. It takes a month.  As long as the annual people feast goes on, says Mr. Walters, “Bella really, really won’t eat her food.”  Write to Laura Meckler at laura.meckler@wsj.com and Stephanie Armour at stephanie.armour@wsj.com
Even if your furry friend isn’t fat—and odds are it is—folks can’t resist letting dogs and other critters join in the feast.