Dramatic effects have been seen from a weight loss recipe that combines anti-addiction drugs with dieting and exercise.

A group of obese trial patients put on the programme lost up to 6% of their bodyweight over the course of a year.

The study authors said the improvements were “clinically meaningful” and may reduce the risk of death.

However, the treatment's success was tempered by a lack of significant reductions in blood pressure and cholesterol levels.

US researchers recruited 1,742 patients aged 18 to 65 for the 56 week trial, but only half saw it through to the end.

Participants were randomly prescribed either a combination of the drugs naltrexone and bupropion or “dummy” placebo pills.

Naltrexone is commonly used to treat alcoholics and heroin addicts, while bupropion is better known as anti-smoking drug Zyban. Both are known to reduce food cravings.

The findings, reported in an online edition of The Lancet medical journal, showed that treated participants lost between 5% and 6% of their bodyweight depending on which of two doses of naltrexone they were given. Patients in the placebo group lost 1.3%.