A new study has found that human and canine obesity share some similarities, according to Science magazine. Obese people have a less diverse array of bacteria living in their guts than do thin people—and the same holds true for dogs.

According to the study abstract, which was published in December 2014 in the "Journal of Veterinary Internal Medicine," seven Beagle dogs were fed commercial petfood over a period of six months to increase their weight and seven other Beagle dogs were fed a restricted amount of the same diet to maintain optimal body condition over a period of six months. Researchers found that the seven Beagles in the first group gained an average of 4.93 kilograms—about 67% of their initial average weight.

"When the researchers examined the fecal samples collected from both groups after six months, they found that the guts of obese Beagles contained a smaller diversity of bacteria than those of the other dogs," said Science magazine. "What's more, microbes from the phylum Firmicutes were the predominant group in the lean dogs, whereas gram-negative bacteria called Proteobacteria were prevalent in the obese group."

The study says that decreased serotonin levels in the obese group might increase the risk of obesity because of increased appetite, and that microflora enriched with gram-negative might be related to chronic inflammation status in obese dogs. However, according to the study authors, more research is needed to examine what role gut bacteria may play in the development of obesity.