An experimental drug by US pharma major Eli Lilly may help people fight obesity and also act as an alternative to bariatric surgery.

The drugmaker claimed that the new drug Tirzepatide has enabled people with obesity or who are overweight to lose about 22.5 per cent of their body weight, about 24 kg on average compared to a placebo at 72 weeks of treatment.

The large trial enrolled 2,539 participants from across the US, Argentina, Brazil, China, India, Japan, Mexico, Russia and Taiwan to evaluate the efficacy and safety of tirzepatide in adults with obesity, or overweight with at least one comorbidity, who do not have diabetes.

On average, participants in the study weighed 105 kg at the outset and had a body mass index (BMI) of 38. At the end of the study, those taking the higher doses of tirzepatide weighed about 81 kg and had a BMI just below 30, on average.

While Eli Lilly is yet to submit the data for publication in a peer-reviewed medical journal or presented them in a public setting, the claims nonetheless amazed medical experts, The New York Times reported.

"Wow (and a double Wow!)" Dr Sekar Kathiresan, chief executive of Verve Therapeutics, a company focusing on heart disease drugs, wrote in a tweet. Drugs like Eli Lilly's, he added, are "truly going to revolutionise the treatment of obesity".

The drug's effect "appears to be significantly better than any other anti-obesity medication that is currently available in the US", another obesity expert at the Massachusetts General Hospital Dr Lee Kaplan was quoted as saying. The results are "very impressive", he added.

They exceed those usually seen in trials of weight-loss medications and are usually seen only in surgical patients, the report said. Because obesity is a chronic medical condition, patients would need to take tirzepatide for a lifetime, as they do for blood pressure or cholesterol drugs, for example.

Diet and exercise, combined with earlier obesity drugs, usually yield perhaps a 10 per cent weight loss in patients. That is enough to improve health, but not nearly enough to make a big difference in the lives of people who are obese.

The only other treatment is bariatric surgery, which can result in substantial weight loss. But many people are ineligible or simply do not want the surgery.