People who walk, bike or take public transportation to work tend to be thinner than those who ride in their own cars, according to a new study from the UK.
The new findings - including that taking public transportation was just as beneficial as the other "active commuting" modes - point to significant health benefits across society if more people left their cars at home, researchers say.
"It seems to suggest switching your commute mode - where you can build in just a bit of incidental physical activity - you may be able to cut down on your chance of being overweight and achieve a healthier body composition as well," said Ellen Flint, who led the study.
Flint and her colleagues from London School of Hygiene and Tropical Medicine and University College London write at TheBMJ.com that physical activity has decreased along with the proportion of people taking active modes of transportation to work.
There is also evidence to suggest greater increases in obesity rates in areas with larger declines in active travel, they add.
Active travel or commuting typically refers to walking or biking to work, but Flint and her colleagues suggest the term should be expanded to include taking public transportation, such as buses and trains.
In their study, Flint said, they found people who reported walking to work weren't walking far - about a mile or less.
"The walking that goes into commuting to public transport is a similar amount," she told Reuters Health.
While there is evidence to support a link between walking and biking to work and reduced weight, there is little research that also looks at people who take public transportation.
For the new study, Flint and her colleagues used data collected from a national sample of people living in the UK who answered survey questions and were visited by a nurse. The researchers had data from 7,424 people on how much body fat they had and from 7,534 on their body mass index (BMI), a measure of weight relative to height.
In the survey, 76 percent of men and 72 percent of women reported taking a private mode of transportation - usually a car - to work. Ten percent of men and 11 percent of women reported using mostly public transportation and 14 percent of men and 17 percent of women walked or biked to work.
After adjusting for traits or behaviors that may influence weight or body fat, such as socioeconomic status and other exercise, the researchers found that people who walked, biked or took public transportation to work had lower average BMIs and body fat percentages than people who used private transportation.
"When you compare public transport to private transport the results are pretty similar to when you compare active transport to private transport," Flint said.
She and her colleagues write that the differences in body mass and fat would be noticeable. For example, men who actively commuted to work or took public transportation had a BMI score between 0.9 and 1.1 points lower than the men who drove themselves. That can be the equivalent of weighing about seven pounds less for a middle aged man of average height.
The men's body fat was also between 1.4 and 1.5 percentage points lower among active and public transport commuters, compared to men who drove.
Similar results were seen for women, whose BMI scores were between 0.7 and 0.9 points lower among active and public commuters compared to women who drove. For a 5-foot 4-inch woman the difference would translate to about 6 lbs.
Amy Auchincloss of Drexel University in Philadelphia said the study's results are strong because its data are from people living in many different areas, although the findings can't prove that walking, biking or taking public transportation causes people to lose weight.
"But at minimum it appears from these preliminary data that not driving/not using automobiles will at least aide populations in healthier weight maintenance - if not directly lead to healthier weight," Auchincloss, who was not involved with the new study, said in an email.
Other studies have also suggested that a more active commute to work has a variety of benefits, according to Anthony Laverty, who co-wrote an editorial accompanying the new study.
"This study focuses on weight," he said. "There are other studies that show people who don't drive to work are less likely to have high blood pressure and diabetes."
"If we had this big shift of people taking public transport, walking or cycling you would have these benefits add up," said Laverty, of Imperial College London.
With obesity prevention already a focus of policymakers, Flint said working on getting more people to walk, bike or take public transportation may be worthwhile.
"In Britain - in common with a lot of industrial nations - the vast majority of commuters use cars. Therefore there is a huge potential for an intervention of access to public transportation for health benefit," she said.
SOURCE: http://bit.ly/YuljgS TheBMJ, online August 19, 2014.