Fitness trackers don’t improve weight loss, study finds

Participants who added ‘wearables’ to diet and exercise plans actually lost fewer pounds than those who stuck with traditional tactics
Wearables are getting scrutiny Stock photo by FeaturePics

They’ll crunch your steps, tally your calories, and measure how long you move or snooze. What fitness trackers won’t do: give you a weight-loss edge, according to a study published Tuesday.

Young adults who are overweight or obese and who added wearable activity sensors to their diets and exercise plans actually lost fewer pounds after two years compared to similar-sized people who stuck just to traditional weight-loss tactics, scientists reported in the Journal of the American Medical Association.

The study involved fitness trackers made by a now-defunct company called BodyMedia but the findings may apply to all mobile health devices, including the popular brand Fitbit, said the study’s authors at the University of Pittsburgh.

“Fitbit and their competitors take note: tracking physical activity and energy doesn’t work when combined with a real diet and physical activity program,” said Dr. Jonathan Bricker, a psychologist and public health researcher at Fred Hutchinson Cancer Research Center who was not involved in the new study.

Researchers followed 471 participants who were between ages 18 and 35 and who had a body mass index of 25 to less than 40. They were each placed on low-calorie diets and prescribed increases in physical activity. They also received group and telephone counseling plus text prompts, and they had access to online study materials.

After six months, about half the participants were randomly placed into a “standard intervention” group that continued following those same, proven weight-loss strategies. The other half was randomly placed into an “enhanced intervention” group that also received the fitness trackers.

Among those in the “enhanced” group, average weight loss after 24 months was 7.7 pounds. Among the device-free participants following the standard methods, average weight loss after 24 months was nearly double — 13 pounds.

“Our findings suggest that (fitness trackers) will not necessarily improve weight-loss efforts beyond what can be achieved with a strong, comprehensive weight-management program,” lead author Dr. John M. Jakicic said via email. He is chair of the department of health and physical activity at the University of Pittsburgh.

'Clearly not helpful' for some 

“For some, (trackers) may be helpful and for others they clearly are not. So, we need to be careful about simply recommending that everyone seeking to lose weight go out and purchase a wearable device,” Jakicic said.

Instead, health advocates should send a message that appropriate nutrition and diet, when combined with sufficient physical activity, must be the centerpieces of weight-loss efforts, he said.

“If a wearable device is helpful then, by all means, use it. But do not simply think that having a device will allow you to pay less attention to these key behaviors to control your weight,” Jakicic said.

Dr. Jonathan Bricker
Dr. Jonathan Bricker Fred Hutch file photo

The University of Pittsburgh study, Bricker said, revealed that fitness devices have “huge limitations.” Roughly, one in eight U.S. consumers own a fitness band or a smartwatch. 

“What we need now is to think carefully about how to make wearables more than just ‘trackers.’ That means designing and testing wearables that get deep into the psychology of what motivates people to stay active, eat healthy and deal with cravings,” Bricker said. He is investigating another type of wearable health device, a smoking-cessation smartphone app called SmartQuit.

“I hope the wearable device companies embrace this study and learn from it,” Bricker said.

Fitbit executives did look at the study on Tuesday. They pointed to past weight-loss metrics reported to the company by its users as proof that the devices can help people shed pounds. 

“The University of Pittsburgh study published in JAMA did not use Fitbit devices or the Fitbit app, so we cannot speak to their specific findings. As the leader in the wearables category, we are confident in the positive results users have seen,” said Lauren Morrison, a media relations specialist who speaks for Fitbit. Among the positive results she cited: Indiana University Health, a Fitbit corporate wellness customer, reported in 2014 that 40 percent of its corporate participants had decreased their BMI over a three-year-period.

So, why did the fitness trackers provided to the study participants fail to help them cut as much weight? 

One answer lies in an exercise study published in 2007 by Fred Hutch researcher Dr. Anne McTiernan and colleagues.

In that trial, conducted to examine the effects of exercise on weight and cancer-related biomarkers, McTiernan and the team found the strongest predictor of weight loss was the number of steps taken per day as recorded on a pedometer. 

Dr. Anne McTiernan
Dr. Anne McTiernan Fred Hutch file photo

“The amount of weight loss produced was quite small — a few pounds over a year. So this just told us that more physical activity produced more weight loss, but the effect was modest at best,” McTiernan said. “If you have a very strong weight-loss intervention — as the new Jakicic paper reported — the amount of exercise isn’t likely to have an effect.”

Should consumers ditch their fitness trackers, which usually retail for between $100 and $250?

“No reason to stop using them, but no reason to spend a lot of money on them either,” McTiernan said. “I’d feel comfortable saying they don’t produce long-term weight loss benefits.

“There are health benefits to being active beyond losing weight, so if a monitor helps you increase the amount of time you spend being active, go ahead and use one,” she said.

McTiernan uses the free fitness tracker on her phone. But the primary data point she watches: time spent exercising. She aims for one hour a day of walking with friends or her husband plus 30 minutes a day on a stationary bike, she said.

What does work for losing weight?

There are scientifically proven methods for cutting pounds and maintaining a healthy weight, McTiernan said.  

The most crucial change is to reduce calories. It’s also important to: monitor your own diet and exercise, whether on paper or online; increase activity; weigh yourself regularly; create weight-loss goals; and seek oversight or guidance from a professional with experience in changing behavior and weight loss, such as a nutritionist or exercise physiologist.

A healthy and typical weight-loss goal is 10 percent of body weight over the first six months.

“We also found that people who prepared their own meals and ate out less often had better weight loss,” McTiernan said. “But that was likely because they were better able to count calories.”

Have a fitness tracker? Has it helped or hindered your weight-loss efforts? Tell us on Facebook.

Bill Briggs is a former Fred Hutch News Service staff writer. Follow him at @writerdude. Previously, he was a contributing writer for and, covering breaking news, health and the military. Prior, he was a staff writer for The Denver Post, part of the newspaper's team that earned the Pulitzer Prize for coverage of the Columbine High School massacre. He has authored two books, including "The Third Miracle: an Ordinary Man, a medical Mystery, and a Trial of Faith." 

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