Fitness trackers have gained popularity in recent years, but it's not clear whether all this tracking is actually helping people become healthier. 

New study suggests the devices can help people become more active. In the study, women who wore a Fitbit saw a boost in their physical activity over a four-month period.

The study involved about 50 women in their 50s and 60s who were overweight and generally not very active. About half of these women were given a Fitbit One, a fitness tracker that clips to a person's waistband and tracks a number of metrics: how many steps they take, the total distance they move, the number of floors they climb, the calories they burn, and the total number of minutes during the day that they are active. 

The other half of the women in the study were given a standard pedometer, which tracks only the number of steps taken. Both groups were asked to try to do 150 minutes of moderate to vigorous physical activity per week. 

The Fitbit group had a little help with their goal-setting — the women decided whether they wanted to start out with a goal of 150 minutes per week, or work up gradually to that goal, and a researcher checked in with them a month later to see if their goal needed to be adjusted. 

The pedometer group was given handouts with tips on how to increase their daily step count.

Sixteen weeks later, women in the Fitbit group were doing an extra 62 minutes of moderate to vigorous activity per week, compared with the amount of activity they were doing before the study started. 

They were also taking an extra 789 steps per day, according to the study. In contrast, women in the pedometer group did not have a meaningful increase in their physical activity during the study. 

It's known that tracking your behavior, and getting feedback, can help change habits, said study researcher Lisa Cadmus-Bertram, an assistant professor of kinesiology at the University of Wisconsin-Madison. 

Both a Fitbit and a simple pedometer provide users with "feedback" in terms of how many steps they are taking per day.

But "the Fitbit provides quite a bit more depth, because it also gives feedback on intensities of physical activity," and the patterns of a person's activity throughout the day," Cadmus-Bertram said. 

The fitness tracker also puts those data in context of the specific goals a person wants to reach, she said. For example, the Fitibit shows users visuals so they can see how much farther they have to go before they meet their goal. 

On the device itself, a flower grows as users become more active, and in the app, users see a circle that fills with color the more active they are.

"It’s a richer and more engaging experience overall," Cadmus-Bertram said.

The new study was small, and included only postmenopausal women, so more studies are needed to confirm the findings, and see if they apply to other populations, the researchers said. 

In addition, the Fitbit group received a little more personal help with their goal-setting than did the pedometer group, and this could have played a role in the activity differences seen between the groups.

The researchers want to conduct a follow-up study where participants are given a little more feedback from an actual person, in addition to the feedback from the fitness tracker. 

Cadmus-Bertram noted that if a device gives feedback based on data that are not accurate, this could be detrimental. "When you get messages that aren't quite right, it's sometimes worse than no feedback at all."

It can be expensive to give people personalized, human coaching, but devices like fitness trackers may help lower the cost, because they can provide data to the researchers, and automate some of the process.

"It’s about taking it to the next level of providing appropriate, responsive support and leveraging the technology to try to create effective interventions that are cheap enough to be used on a broad scale," Cadmus-Bertram said.

The study was published online June 10 in the American Journal of Preventive Medicine.