The author call the dental chews she gives her dog "guilt-a-bones," because she can't help but give her one every time she leave. Picture: Jenna Gallegos, Washington Post

Washington - Losing weight is tough. It would be easier if a benevolent someone concerned about your health controlled exactly how much you ate and how often you exercised, right? That's the situation for most dogs and cats, and yet the majority are overweight or obese.

As with our own dieting woes, the unpleasant prospect of the simple solution - feeding our furry friends less - makes us reach for alternative, quick-fix strategies. Many pet parents have turned to radically new menus. These grain-free, all-meat and raw-food diets are inspired by the meals eaten by wild relatives of our fidos and felixes.

But are these diets really better for our pets? Veterinarians and pet nutrition researchers say probably not.

According to clinical veterinary nutritionists at Tufts University, grain-free foods were one of the fastest-growing sectors of the pet food market in 2016. "All I ever hear is, oh, on a good diet, it's grain free," said Dena Lock, a veterinarian in Texas. The majority of her pet patients are overweight.

Why have these pet diets become so popular?

"It's a marketing trend," Lock said.

"Grain-free is marketing. It's only marketing," said Cailin Heinze, a small-animal nutritionist at Tufts University's Cummings School of Veterinary Medicine. "A lot of foods market themselves by what they're not including," and the implication is that the excluded ingredient must be bad.

"Grain-free is definitely a marketing technique that has been very successful," said Jennifer Larsen, a clinical nutritionist at the University of California Veterinary School in Davis. (Disclosure: I went to graduate school at the University of California at Davis, but studied plants, not pets.) People think that if they pay a lot for food and there are a lot of exclusions on the bag, that the food is healthier, but "they're buying an idea," she said, "not necessarily a superior product."

There is absolutely no data to support the idea that grain-free diets are better for pets, Heinze and Larsen noted.

Some pet owners have a false impression that grains are more likely to cause an allergic reaction, but "it's much more common for dogs to have allergies to meat than to grain," Heinz said. Chicken, beef, eggs, dairy and wheat are the most common allergies in dogs. And it's not that there's anything particularly allergenic about these foods, she said, they're just the most frequently used ingredients.

Many grain-free pet foods are made with starch from potatoes or lentils and they may be higher in fat. If you cut grains but increase calories, your pet is going to gain weight, Heinze said.

Dogs and cats also have a drastically different lifestyle from wolves or tigers. Pets are almost always spayed and neutered which is in itself a risk factor for obesity. And most live inside or in pens, so their energy needs are reduced dramatically.

Experts especially caution against feeding pets raw meat. "It's not uncommon to find things like salmonella and E. coli and listeria in raw meat," Larsen said. There are a lot of microbes present in our farming systems, and unlike when an animal is hunting in the wild, there are many opportunities for bacteria to contaminate meat between the time an animal is slaughtered and when it reaches our kitchens.

Raw diets tend to be lower in fibre, and high fiber probably results in larger stools. But we don't have a sense of whether stool quality and quantity correlate with health, Fascetti said. And that shiny coat probably is because of high fat, Heinze said.

If pet owners wish to formulate their own diets, they should work with their veterinarian and a board-certified nutritionist. If you're feeding your pet a balanced diet such as in a commercial chow, obesity is the biggest nutrition issue pet owners should worry about, Heinze said.

We want our pets to enjoy what they're eating, so many foods and especially treats are formulated to be high in fat, Larsen said. Most people don't realize that a milk bone has about as many calories as a candy bar, Lock said.

I know the struggle. My own hefty husky mix stares at me with her big brown eyes and licks the window whenever she wants food. I've taken to calling the dental chews I buy her "guilt-a-bones," because I can't help but give her one every time I leave.

But studies have found that feeding dogs to maintain a lean body weight has very positive effects on their overall health and can even increase life span. This is also the case in mice and rats, and "we believe that these findings apply to cats as well," Fascetti said.