A combined course of two treatments has double the slimming power of leading anti-obesity pill orlistat, according to research.
Trial users also experienced a number of other health benefits, including lower blood pressure and reduced harmful fatty molecules and sugar in the blood.
The study, published in the The Lancet, tested two drugs – phentermine and topiramate – on almost 2,500 overweight and obese adults from 93 US centres.
Participants in the trial were split into different groups to receive either varied doses of the treatments or a 'dummy' placebo.
Results from the Conquer Phase III trial revealed that patients on higher doses of the drugs lost 10.2 kg, or 22 pounds, on average.
A majority of 70% of those on the higher dose achieved a 5% weight loss, compared with 61% on the lower dose and 21% for those in the placebo group.
These findings show that the course of treatment is more effective than orlistat, which is currently the only anti-obesity drug available on the NHS.
In some diabetic patients, it achieved more than double the weight loss seen after up to four years treatment with orlistat.
The scientists, led by Dr Kishore Gadde, from Duke University Medical Centre in Durham, US, wrote: "Most importantly, weight loss achieved with phentermine and topiramate was sustained during 56 weeks with improvements in blood pressure, lipids (blood fats), glycaemia (blood sugar) and inflammatory markers.
"The combination of phentermine and topiramate, with office-based lifestyle interventions, might be a valuable treatment for obesity that can be provided by family doctors."