The apps that claim to help lose weight
January is a peak time for downloading health and fitness apps and putting those Christmas present fitness trackers to work. But do they actually help you stay motivated?

After the Christmas self-indulgence comes the inevitable New Year's resolution to get fit, lose weight, and eat more healthily.

But while 65% of us make resolutions, only 12% successfully keep to them, polling firm ComRes finds. Can tech help?

When Sarah, 34, a law professor from Australia, wanted to lose weight last year, she took the unusual approach of placing bets that she would achieve her exercise goals.

Breast cancer had stopped her exercise routine, and she'd gained weight during a year which included three operations, she says.

"I was returning to exercise by hiking and trying to lose some of the weight I'd put on while being sedentary," she says.

She began a new exercise routine eight weeks after finishing breast reconstruction surgery. With a wearable activity tracker, she monitored the steps she took each day and the calories she burned.

But she also motivated herself with an app, Step Bet, that let her wager whether she would achieve her exercise goals.

"I did three one-month bets and three six-month bets, and lost 7kg [15 lbs] - 10% of my body weight," says Sarah.

She also says she made £358 [$458; €403].

"I like losing fat. I don't like losing money. The effect? Motivation!" she explains.

For the data-minded, tracking your progress with reams of measurements is enough to stay motivated.

Arshia Gratiot, who is 40 and originally from Bangalore, has been using a fitness tracker for a year, "to measure biometrics such as my heart rate, associated with my level of fitness," she says.

In 2016, she founded a technology start-up with offices in Finland, India, and London. 

Frequently travelling across time zones made her decide to go running each evening - sometimes in the middle of the night - while listening to podcasts.

"It was either lie in bed like a zombie, totally jet-lagged, or hit the road. It was the only way I could stay sane," she says.

Tracking her heart rate and metabolism offered "a visual way to track progress over time" and encouraged her, says Ms Gratiot.

But it's how we use such data that matters, argues Anil Aswani, an assistant professor in industrial engineering and operations research at the University of California, Berkeley.

"Personalized goal setting is a very important aspect of these apps," he says

The better exercise apps learn from how you've done in the past to tailor your goals, he argues. And doing this builds a sense of achievement, which behavioural psychologists say is important in altering your habits.

"If you're effective at meeting goals today, it boosts your confidence and makes you more likely to meet your goals in the future," says Prof Aswani.

In his own research, one group of test subjects was given a changing number of steps as a goal each day, based on their previous progress. Another was assigned the same number of steps every day.

The group given adaptive goals averaged about 1,000m more each day, he says.

Joseph Laws, a former US army Ranger who served in Afghanistan and afterwards worked as a software engineer at Google, has developed his own way of setting adaptive goals.

Based on his army experience, he began developing fitness routines for friends and family. Later, he started developing machine learning algorithms to find out which exercises best built fitness, based on age, sex, height, and weight.

Mr Laws released the official version of his app, Optimize, six months ago.

The challenge was "developing a model of fitness, and mapping those equations to actual exercises," he says.