Shopping vouchers and online social networks may be powerful, modern tools to help people quit smoking and lose weight, two unusual experiments suggest.
Pregnant women promised vouchers were much likelier than non-rewarded peers to kick the smoking habit, a study in Scotland showed.
And American researchers found that people shed more kilos the more online friendships they formed with fellow weight-watchers.
Both projects sought to find innovative and cost-effective ways of tackling lifestyle behaviours that are inflicting an ever-heavier toll in lives lost and healthcare costs around the world.
In the Scottish study, published in The BMJ on Wednesday, researchers offered 612 pregnant smokers in Glasgow free nicotine replacement therapy and professional quitting aid.
Half the volunteers were also promised STG400 ($A766) in shopping vouchers.
A first voucher of STG50 was earned for showing up for a meeting with a professional and setting a quit date, another STG50 for not smoking for four weeks, another STG100 for 12 weeks and STG200 at 34-38 weeks.
Saliva or urine tests were used to confirm abstinence from cigarettes.
"Significantly more" of the voucher recipients stopped smoking - 69 out of the first group of 306, compared to 26 from the non-rewarded half, said the study - 23 per cent and nine per cent respectively.
"After 12 months, 15 per cent of women who were offered financial incentives remained off cigarettes compared to only four per cent" of the other group, said a statement.
Most of the women were from lower-income categories, but study co-author David Tappin of Glasgow University said the idea of a financial incentive "seems to work in all groups".
Scaling up the experiment would cost lots of money - but the bill should ultimately be far cheaper than the soaring cost of smoking-induced foetus and infant deaths and illness, the team argued.
Some 5000 miscarriages a year can be attributed to smoking during pregnancy in Britain alone.
In the other study, published in the journal Proceedings of the Royal Society B, researchers in the US looked at more than 2000 people who joined an online weight management (OWM) social networking site.
After six months, people with a single contact reported having lost on average 4.1 per cent of initial body weight, rising to 5.2 per cent for those with two to nine friends.
It rose further to 6.8 per cent for those with a bigger group of contacts, and a whopping 8.3 per cent for those with the highest connectivity.
Previous research had found that meetings in real life, where like-minded people offer each other tips and support, are highly effective against bulging waistlines.
But cyber support, too, may be an answer, the authors said.
"OWM programs hold the potential to foster the spread of weight loss among large numbers of people at low cost," they wrote.
"It is essential to continue exploring and optimising this important new tool in the arsenal of public health interventions."
Over half a billion adults worldwide are considered obese, a condition closely linked to cardiovascular disease, diabetes and cancer, said the study.
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