Fitness trackers from Fitbit, Garmin, and other manufacturers are big business. Millions of the devices are sold each year to help people monitor their physical activities and the number of calories burned. But how effective are they in actually improving an individual’s health?

According to Dr. Greg Hager, an expert in computer science at Johns Hopkins University, users should be particularly aware of devices that track people’s steps and advise them to walk 10,000 steps a day, which equals about five miles. Hager explained at the American Association for the Advancement of Science annual meeting that the 10,000 steps protocol was birthed from a study examining Japanese men dating back to 1960.

Hager said, "Some of you might wear Fitbits or something equivalent, and I bet every now and then it gives you that cool little message, 'You did 10,000 steps today.' But why is 10,000 steps important? Is that the right number for any of you in this room? Who knows? It's just a number that's now built into the apps. I think apps could definitely be doing more harm than good."

Even the official Fitbit blog acknowledges that 10,000 steps a day is not a one-size-fits-all strategy. "10,000 steps per day might not make sense for you. You may need to nab more if you want to lose a certain amount of weight, or take fewer steps if you’re new to fitness or recovering from an injury," writes fitness editor Lara Rosenbaum. "Your step goal can vary depending on your needs, and it can also shift over time."

A 2016 study from the University of Pittsburgh School of Education’s Department of Health and Physical Activity concluded that fitness trackers alone are not a reliable tool for losing weight and should not replace behavioral counseling, diet and physical activity. In fact, the study revealed that participants who didn’t use fitness trackers showed nearly twice the weight loss benefits at the end of a 24-month trial.

Lead author John Jakicic explained, "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. 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."

The study participants were put on low-calorie diets and were asked to exercise more. After six months, half of the 470 participants were given fitness trackers. After two years, those with the devices lost less weight — 7.7 pounds compared to 13 pounds.

Jakicic added, "These technologies are focused on physical activity, like taking steps and getting your heart rate up. People would say, 'Oh, I exercised a lot today, now I can eat more.' And they might eat more than they otherwise would have."

He also believes that while meeting daily fitness goals and step counts may motivate some people, others may become discouraged.

That doesn't mean people should completely give up walking 10,000 steps a day. A 2010 study published by The National Center for Biotechnology Information showed that walking "improves cardiovascular performance and personal growth and also positively influences many variables that are indicators of health, fitness and psychological well-being." In addition, walking briskly can lower a person’s risk of high blood pressure, high cholesterol and diabetes, which are risk factors for heart disease and stroke.

If fitness trackers help motivate people who otherwise wouldn’t be physically active, than they are providing a good service. The American Heart Association recommends that adults do 30 minutes of physical activity a day, 150 minutes of moderate activity per week or 75 minutes of vigorous activity per week.