Fitness trackers play a crucial role in some people’s weight loss plans, but new research suggests they may not help. The study, which was published in JAMA and covered by NPR, found that people wearing a fitness tracker while following a standard weight loss plan lost less weight than people using other tracking techniques. The 471 study participants were between the ages of 18 and 35 and had body mass indexes (BMIs) from 25 to 39, which is considered overweight. Participants were assigned a low-calorie diet, gradually increasing amounts of exercise, and group counseling sessions. After six months, researchers added phone counseling sessions, text messages prompting healthy behaviors, and access to online study materials. Also at six months, researchers randomly assigned the participants to track their diet and exercise either online or via a wearable fitness tracker and app. Every six months for the rest of the two-year study, researchers measured both groups’ changes in weight, BMI, cardiorespiratory fitness, physical activity level, and diet. At the end of the study, they found that:
Participants with a fitness tracker lost significantly less weight than participants without a fitness tracker: On average, those wearing one lost 7.7 pounds, while those not wearing one lost 13 pounds.
All participants had significant improvements in BMI, cardiorespiratory fitness, physical activity level, and diet, with no difference between the two groups.
It’s unclear why wearing a fitness tracker was associated with less weight loss. One explanation may be that, since fitness trackers log physical activity stats like steps and heart rate, participants may have felt they could eat bigger portions on days they exercised more. Another reason may be that closely tracking exercise was discouraging, rather than encouraging, when goals weren’t met. Does this mean you should throw out your device? Not necessarily. While they may not be for everyone, they could help motivate people who are already dedicated to tracking their fitness.