In the wake of COVID-19, it is easy to forget that America is also dealing with another epidemic. Between 1990 and 2018, the percentage of adults in the United States considered clinically obese quadrupled from 11% to 40%. According to a study in the American Journal of Public Health, nearly one in five deaths in the country each year are obesity-related. Experts disagree about the causes of the increase in the average weight of Americans, but they agree on the health consequences. Obesity is associated with high blood pressure, type 2 diabetes, heart attacks, strokes, depression, sleep apnea, and 13 kinds of cancer. No wonder doctors tell their patients to shed the pounds.
But while losing weight is relatively easy in the short run, keeping it off is difficult and, for many people, it is nearly impossible. Could pets help fight the obesity health crisis? Perhaps, if you believe headlines such as “Studies Show Having A Dog Can Help Drive Weight Loss.”
A report commissioned by the Human-Animal Bond Research Institute claims dog ownership is responsible for a million fewer cases of obesity in the United States annually. Further, the report claims, “The reduction in health costs associated with a lower incidence of obesity among American dog-owners is more than $419 million per year.”
The idea that pet ownership translates into lower doctor bills assumes that pet owners are less susceptible to obesity than non-owners. But is this true? A team of Japanese researchers recently reviewed 21 studies on the link between pet-keeping and obesity. Published in the International Journal of Environmental Research and Public Health, their results were fascinating.
Studying the Studies
Hundreds of papers on the impact of pets on human health and happiness are published each year, but they often produce inconsistent results. For example, in a 2008 report, Australian researchers found that kids raised with pets had lower levels of obesity. But a similar study in the United Kingdom by Dr. Carri Westgarth's research group found no differences in the obesity rates of children who had pets and children who did not.
Inconsistent research results are common in science. That’s why investigators usually don’t take the findings of a single study too seriously. Rather, they look for the patterns of results over multiple studies. To do this, investigators conduct a “study of studies.” A widely used method for comparing the results of different studies is called a systematic review. Researchers also use a statistical technique called meta-analysis to combine the results of studies on the same topic. The Japanese research team used both techniques to evaluate research on the relationships between pet ownership and obesity.
The researchers located 21 published studies comparing obesity rates between people who lived with any kind of pet and non-pet owners. In all, 218,192 people participated in the studies. Several of the studies examined differences in obesity by age groups. The researchers evaluated the results of 25 separate comparisons between pet-owners and non-owners.
They found that in 17 of the 25 comparisons, living with a pet made no difference in obesity rates. Three of the studies, however, reported that pet owners were more likely to be obese, while five of them found that pet owners were less obese. The researchers were able to combine the results of nine studies using meta-analysis. They reported that when pooled over 24,555 subjects, the chances a pet owner was obese were no different than those of a person who did not have a pet. (For stat geeks, the pooled Odds Ratio = 1.038).
What About Dogs?
I was not surprised by these findings. After all, the category “pet owners” includes people who have pets that you would not expect to provide opportunities for exercise and weight loss—cats, fish, birds, hamsters, and even pet rats and snakes. But I figured dog owners might be different. After all, a 2019 study found that dog owners spent twice as much time each week walking as people who did not have a dog.
Fortunately, 18 of the studies only included people who lived with dogs. By analyzing these studies separately, the researchers were able to test the hypothesis that dog owners are less likely to be obese than people who did not have pets. They found this was not the case. The pattern of results in the dog-owner-only studies was the same as for the “all pets owners.” Thirteen of the dog studies found no differences in levels of obesity in pet-owners and people who did not have pets. Two reported that dog owners were more likely to be obese, and in three of the studies, dog owners were less prone to obesity. A meta-analysis of seven of the dog studies found that the chances that dog owners would be obese were the same as for people with no pets (pooled Odds Ratio = 1.001).
Three of these studies involved children. When the kids' data were pooled, a meta-analysis revealed no differences in obesity levels in children who lived with dogs and kids who did not.
The Bottom Line
After reviewing the results of 21 studies from seven countries involving over 200,000 subjects, what did the research team conclude? They wrote, “There was no significant association between pet ownership and obesity regardless of age group. Furthermore, no association was observed between dog ownership and obesity.” These findings pull the rug out from the pet industry claims that companion animals save Americans nearly half a billion dollars a year in obesity-related health care costs.
As I have said before in this column, there are lots of reasons to bring a pet into your life. But losing weight may not be one of them.
Miyake, K., Kito, K., Kotemori, A., Sasaki, K., Yamamoto, J., Otagiri, Y., ... & Ishihara, J. (2020). Association between Pet Ownership and Obesity: A Systematic Review and Meta-Analysis. International Journal of Environmental Research and Public Health, 17(10), 3498.
Timperio, A., Salmon, J., Chu, B., & Andrianopoulos, N. (2008). Is dog ownership or dog walking associated with weight status in children and their parents?. Health Promotion Journal of Australia, 19(1), 60-63.
Westgarth, C., Heron, J., Ness, A. R., Bundred, P., Gaskell, R. M., Coyne, K., ... & Dawson, S. (2012). Is childhood obesity influenced by dog ownership? No cross-sectional or longitudinal evidence. Obesity Facts, 5(6), 833-844.