Those who have them – and millions do – swear by them, but a new study suggests fitness trackers that monitor physical activity don’t actually make any difference when trying to lose weight.

In fact, according to the two-year study, which monitored nearly 500 people during a behavioral weight loss program, those who didn’t wear a weight loss tracker lost nearly twice as much weight as those who did.

The study, published in the Journal of the American Medical Association, set out to investigate whether commercially available activity trackers are actually effective for initiating and sustaining weight loss.

Unfortunately for those looking for a quick fix, they concluded that wearable devices that monitor and, in some cases, provide feedback on physical activity, do not offer any kind of advantage over standard weight loss approaches of diet and exercise.

The researchers, from the University of Pittsburgh, followed 470 overweight or obese people aged between 18 and 35 who were put on a low-calorie diet, given an exercise plan, and offered counseling sessions on diet and nutrition. After six months, the group was split into two, with half offered monthly health counseling sessions but otherwise left to monitor their progress themselves, and the other group receiving wearable devices to track their physical activity and diet.

Over the following 18 months, both groups showed significant improvement in their overall health, with no marked difference, except for weight loss. The group who wore the fitness trackers averaged a loss of 3.5 kilograms (7.7 pounds) over the 2 years, while the group who didn’t averaged a loss of 5.9 kilograms (13 pounds).

_{This isn't really how they work... Monkey Business Images/Shutterstock}

The researchers warn that although they can make it easier to track your physical activity, people can become overly dependent on their gadget and lulled into a false sense that they are being proactive just by wearing the device and monitoring themselves, rather than making any actual changes in their lifestyle and habits.  

“While usage of wearable devices is currently a popular method to track physical activity – steps taken per day or calories burned during a workout – our findings show that adding them to behavioral counseling or weight loss that includes physical activity and reduced calorie intake does not improve weight loss or physical activity engagement,” said Dr John Jakicic, lead author and chair of Pittsburgh’s Department of Health and Physical Activity, in a statement.  

“Therefore, within this context, these devices should not be relied upon as tools for weight management in place of effective behavioral counseling for physical activity and diet.”

As to why this could be the case, Dr Jakicic suggested it could be as simple as people who use fitness trackers become fixated on their exercise goals and ignore other aspects of a healthy lifestyle, like diet advice.

"You might think to yourself, 'I'm being so active I can eat a cupcake now,'" he told the BBC.

The rise in wearable technology is undeniable, with sales of fitness trackers, smart watches, and downloads of pedometer apps seeing sharp increases. Unsurprisingly, representatives of the popular health tracker devices are pointing out that anything that encourages people to do more physical exercise is a good thing.

A spokesperson for Fit Core – the fitness tracker used in the study – told the Daily Mail: “The results of the study do not suggest that wearable devices should not be used for positive weight-loss outcomes.

“In fact, the study demonstrated positive weight loss in both groups. Wearable tech helps to bridge the gap between patients who have access to rather intensive weight loss treatments and the very many who don’t.’”