It is said that if you reach for the Moon and miss, you will at least end up among the stars.
And for people hoping to shed the kilos next year, setting out with unrealistic expectations could be the key to losing weight.
A study of 24,000 obese people who were on a 12-month slimming programme found that those with an ambitious "dream weight" target dropped an average of 20 kilos, around 19 per cent of their body weight. In contrast, slimmers who set themselves "achievable" goals lost much less.
The study, carried out by the University of Nottingham on behalf of Slimming World, challenges NHS advice that overweight and obese people should aim to lose 5 to 10 per cent of their body weight.
Instead, authors say slimmers planning a new year purge should "shoot for the Moon" to gain the best results, and are calling for a review of the current guidance.
"January is the most popular time of the year to start a healthy weight loss programme and so it's really important that people have the information they need to maximise their chances of success," said study author Amanda Avery, an academic in nutrition and dietetics at Nottingham University and consultant dietitian for Slimming World. "We know that current NHS and National Institute for Health and Care Excellence (Nice) advice around realistic weight loss targets is designed to protect slimmers from disappointment.
"However, suggesting that people place limits on their weight loss aims could stop people from seeing what they're capable of. It's important that people have aspirations and can visualise themselves achieving success.
"This will help with their motivation as, if it is really their dream weight, they'll be far more committed to achieving it."
In Britain around a quarter of people have an obese Body Mass Index (BMI), meaning that their weight could be seriously affecting their health.
In 1975 the average Briton had a BMI of 23, considered a healthy weight. But today that has risen to 27, with the average person now overweight.
The new study, published in The Journal of Human Nutrition, showed that people who set a target of losing 27 per cent of body weight lost an average of 19 per cent. Those who set a target of around 16-21 per cent hit 14 per cent, while those who set a target of 10 per cent only achieved their goal amount.
The NHS said current guidance had been set to stop people feeling disappointed and giving up when they realised they would not achieve their goal.