The must-have fitness gadgets that could make you fatter

Unlike the purely decorative loom band, these sleek rubber bands — some with a watch-like face, some just a simple bracelet — have a function.

Acting like mini personal trainers, these high-tech pedometers register calories burned, steps taken, distance travelled and even how well you’ve slept, handily logging all of the data on to an app on your smartphone.

They’ve been a huge hit with fitness freaks and desperate dieters alike, and look set to become even more prevalent as both Apple and Google launch their versions this year.

By 2018, it’s estimated that 130 million fitness trackers will have been sold worldwide — and they’re particularly popular in the UK, with more Britons wearing one than in any other country in Europe.

But sales figures aren’t the only things on the up. A growing body of rather worrying research suggests that, when it comes to counting calories, some of these high-tech, high-priced gadgets — which start at around £80 and can cost several hundreds of pounds — could, in fact, be completely wide of the mark.

Just last week, a study by Iowa State University in the U.S., revealed some of the bands could overestimate wearers’ calorie burn by as much as 40 per cent — a huge margin of error when you’re trying to work out how many calories you should be consuming.

Could this be why a raft of dieters on weight-loss forums across the web are joining discussions entitled such things as ‘My Fitbit [one of the most popular brands] is making me fat!’ with tales of gaining, rather than losing, pounds?

As someone who has become a devotee of the gadgets over the past six months, I didn’t want to believe the stories.

As the editor of the women’s health website healthista.com, I get sent new health products to test every day.

After a stint trialling the Nike+ FuelBand (£89, nike.com) — dubbed the A-list fitness accessory by Vogue, no less — I had become obsessive about tracking my calories and steps, and competing with myself to increase my daily activity.

But despite my slavish devotion to the technology, even I had begun to have my doubts.

(dailymail.co.uk)