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The key to losing weight could be as simple as drinking a pint of water before mealtimes , researchers have said.

A study in which obese adults consumed 500ml of water half an hour before eating main meals saw them report an average loss of 4.3kg (9.48lbs) over a 12-week period.

Researchers at the University of Birmingham said the simple trick could be hugely beneficial, and easily promoted by healthcare professionals and through public health campaigns.

The trial saw obese adults recruited from GP surgeries and monitored for 12 weeks.

Each of the participants was given a weight management consultation, where they were advised on how to adapt their lifestyle and diet and improve their levels of physical activity.

Around half were also asked to "pre-load" before meals with water, and half advised to imagine that they had a full stomach before eating.

Those in the first group lost 1.3kg (2.87lbs) more than those in the control group on average.

(Image: Getty)

Participants who reported pre-loading before all three main meals of the day reported a loss of 4.3kg (9.48lbs) over the 12 weeks, whereas those who only pre-loaded once, or not at all, only lost an average of 0.8kg (1.76lbs).

They were encouraged to drink tap water as sparkling water, sodas or sweetened drinks were not allowed as part of the study.

Dr Helen Parretti, National Institute for Health Research (NIHR) clinical lecturer at the University of Birmingham, said: "The beauty of these findings is in the simplicity.

"Just drinking a pint of water, three times a day, before your main meals may help reduce your weight.

"When combined with brief instructions on how to increase your amount of physical activity and on a healthy diet, this seems to help people to achieve some extra weight loss - at a moderate and healthy rate.

"It's something that doesn't take much work to integrate into our busy everyday lives."

The research is published in the journal Obesity.