Choose walking, biking and public transportation over driving may be a wise decision if you do not want to gain any more weight, as a new study suggests that people who drive to work tend to be heavier than people who use other modes of transportation.

Researcher Ellen Flint at the London School of Hygiene & Tropical Medicine in England and colleagues reviewed data on more than 150,000 participants between the ages of 40 and 69. They compared the weight differences between the adults based on how they commuted to work.

The researchers found that men who biked to work had a body mass index (BMI), which measures obesity based on one's weight and height, that was 1.7 points lower than the BMI recorded in the group of male adults who drove. The difference was also apparent in women, as women who biked had a BMI that was 1.65 points lower than women who drove. In terms of weight, people from the biking group, in general, tended to weigh less than the people from the driving group. The researchers also found, as expected, that the distance to work affected the degree of health benefits in people who did not drive.

After biking, the mode of transportation that led to the second greatest dips in BMI and weight was walking. People who walked generally had a BMI that was around one point lower than the BMI recorded in people who drove. When the researchers examined the health benefits of using public transportation, they were surprised to find that this group of people also had a lower BMI and weight when compared to the driving group.

"We found that, compared with commuting by car, public transport, walking and cycling or a mix of all three are associated with reductions in body mass and body fat percentage, even when accounting for demographic and socioeconomic factors," Flint said. "Many people live too far from their workplace for walking or cycling to be feasible, but even the incidental physical activity involved in public transport can have an important effect."

The associations between transportation and health persisted even after factors such as income, education level and smoking were accounted for. The researchers reasoned that the differences between the participants' health could be attributed to higher physical activity levels. People who have to move more to get to work might be burning additional calories and getting their heart rates up.

The study was published in the March 16 issue of the journal The Lancet Diabetes & Endocrinology.