The United States faces a growing weight problem, and it’s crossed species lines.
Twenty-seven years ago, only about 1 in 6 people in the country were obese. Since then, that rate has more than doubled — to more than 1 in 3 — according to the Centers for Disease Control and Prevention. Obesity is a problem associated with a raft of medical conditions that include heart disease, cancer, and type 2 diabetes. It’s also become an area of interest for microbiologists, who in recent years have published studies that connect serious medical conditions to a bacteria imbalance in the intestines. Knowledge of the relationship between diet and gut flora could help shape treatments or nutrition guidelines.
The obesity epidemic is also, increasingly, a problem for our pets. The Association for Pet Obesity Prevention, or APOP, conducts an annual survey of veterinarians in the U.S., and the group’s most recent published numbers estimate that 54 percent of dogs and 58 percent of cats are overweight or obese. In pets as in people, it follows that a better understanding of the gut microbiota of furry friends could help us make better decisions about their diets. Biologists have only recently begun to explore this research area.
“There are many gut microbiome studies on humans and rodents, but not a whole lot on dogs, in particular,” says Johnny Li, a computational biologist at the Nestle Purina PetCare Company, in St. Louis. He recently led a study on the connection between diet and intestinal bacteria on 64 dogs — 32 Beagles and 32 Labrador Retrievers. Half the dogs in the study were obese or overweight, and half were lean or of normal weight. Li sees his study as an initial step toward using microbiotic information to customize pet diets.
All the dogs ate the same diet for four weeks; afterward, Li and his collaborators used fecal samples to get a baseline analysis of the canines’ gut microbiomes. Then, the dogs were fed a diet for four weeks that was either high in protein and low in carbohydrates, or vice versa. At the end of this second phase, the scientists again analyzed the microbiomes to look for changes. All diets provided all the nutrient requirements for the dogs.
They report this week in mBio that a high protein, low carb diet doubled the abundances of three Gram-positive bacteria: C. hiranonis, C. perfringens, and R. gnavus. The first is believed to be associated with bile acid metabolism. Abundance of the second, in a previous study on over 150 dogs, has been associated with healthy dogs and is likely commensal. The third is a common core species of the human intestines. A low protein, high carb diet favored other species — specifically B. uniformis and C. butyricum.
Li says his group’s study, on its own, is insufficient to make broad recommendations for how to manage a pet’s obesity through its diet. However, their tests do suggest the findings apply to large and small breeds alike. And in yet-unpublished data, the researchers found that a high protein, low carb diet can reduce weight gain in lean dogs without cutting down on calories.
Li says he hopes that this study provides a framework for exploring how adding probiotics or prebiotics to an animal’s food might help keep its weight under control. He also leaves open the possibility for doing similar studies on other animals. “Maybe in the future we’ll do cats,” he says.