Researchers say fitness trackers can help people to lose weight and reduce their body mass index (BMI).

Experts from the University of Minnesota Twin Cities in the US examined previous research on the topic, analysing data on 31 studies, which included a total of 2268 people.

Each study varied in length - between four and 52 weeks - and required participants to set and meet goals based on daily steps and/or to reach the recommended weekly minimum of 150 minutes of moderate-to-vigorous intensity physical activity - usually through brisk walking.

They found people who used trackers for at least 12 weeks were likely to reduce their BMI and lose weight.

The study, published in the British Journal of Sports Medicine, found that research-grade step counters or accelerometers by themselves resulted in the most weight loss - an average of 4.4 kilograms - while the commercial fitness trackers by themselves produced an average loss of nearly 3kg.

Both types of devices by themselves resulted in a reduction of BMI but the result was even more profound when the wearers were also given counselling and advice on dietary changes.

"While research grade step counters and accelerometers aren't available to the public, commercial wearable fitness trackers are, and represent a practical option for people who are overweight/obese and who have weight-related conditions," the researchers said.

Australian Associated Press