Activity trackers fall short in weight-loss trial

In surprising result, those who didn’t monitor steps lost more pounds

Jogger with fitness tracker

TECHNOLOGY FAIL  In a two-year trial, people who wore activity monitors lost less weight than people who didn't wear the devices. 


Carefully counting steps, stairs and sprints might backfire for some people. At the end of a two-year weight-loss trial, people who used activity monitors had lost less weight than people without the device. The results, described in the Sept. 20 JAMA, are the exact opposite of what researchers expected to find.

Going into the study, researchers thought that wearable technology would help people, particularly tech-savvy young adults, keep extra weight off. “It turns out that it actually worked against us,” says study coauthor John Jakicic, a weight-management researcher at the University of Pittsburgh.

Jakicic and colleagues followed 470 overweight or obese young adults, ages 18 to 35, over two years as they completed a weight-loss program that focused on healthful eating, exercise and support through meetings, phone calls and texts. During the first six months, participants lost fairly comparable amounts of weight.

The real challenge, though, is in keeping extra weight off. And that’s why researchers turned to an exercise monitor. At the six-month mark, half the participants received an armband device that monitored their activity levels, providing readouts to both participants and researchers. But unexpectedly, by the end of the study, people without the device had maintained a better weight loss — 5.9 kilograms on average, or about 13 pounds. People with the device lost only 3.5 kilograms on average, or about 7.7 pounds.

Other factors, however, such as overall fitness, body fat and diet were similar for both groups at the study’s end. These factors “are just as, if not more, important than solely weight,” points out developmental psychologist Amanda Staiano of Louisiana State University’s Pennington Biomedical Research Center in Baton Rouge. It’s puzzling why only weight seemed to be affected by the technology.

“We’ve been scratching our heads,” Jakicic says of the finding. He and colleagues have a few possible explanations. Perhaps the device encourages people to lean too heavily on the technology and its emphasis on moving, and users let other aspects of weight loss slip. “Everyone is looking for a magic bullet,” he says, but weight loss is hard. Or, instead of getting motivated by a challenge, people trying to lose weight might be discouraged if their activity level readouts are low. What’s more, after a few months of using the gadget, people might become bored and stop using it as much. “Maybe these technologies lose their luster,” Jakicic says. “If you’re not wearing it, it won’t be helpful to you.”

A lack of engagement could help explain the results, says physical activity epidemiologist Lisa Cadmus-Bertramof the University of Wisconsin‒Madison. “Technology can be helpful, but we should absolutely expect that it could backfire if the device isn’t ideal,” she says. On days when people wore the armband monitor, they typically wore it for only about four hours — far less than people usually wear a wristband Fitbit, she adds.

The good news is that a small number of people with the technology kept off more weight than the average of people with the device. Jakicic and colleagues are analyzing why those people seemed to benefit while others did not.

A strength of the new study is its focus on young adults, about a quarter of whom were not white. Young people, and particularly young minorities, are “in need of creative, effective strategies to combat their historically high rate of obesity,” says Staiano, who is also a spokesperson for the Obesity Society. Because young adults spend much of their days using technology, scientists shouldn’t give up attempts to figure out how to enlist devices to help manage weight, she says. Today’s gadgets, which look like jewelry on the wrist and can track not just activity but also diet, sleep and mood, may still hold promise.  

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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