Wegovy, also known as semaglutide, mimics a hormone released by the body after a meal to flip one appetite switch in the brain. Mounjaro, or tirzepatide, flips two.

The trial, which was paid for by Eli Lilly, the manufacturer of Mounjaro, involved 750 obese people, with an average weight of 113kg (nearly 18 stone).

They were asked to take the highest dose they could tolerate of one of the two drugs.

The findings, presented at the European Congress on Obesity in Malaga and in the New England Journal of Medicine, external, showed:

32% of people lost a quarter of their body weight on Mounjaro compared to 16% on Wegovy

Those on Mounjaro lost an average of 18cm from their waistlines compared with 13cm on Wegovy.

Those on Mounjaro had better blood pressure, blood sugar and cholesterol levels.

Both had similar levels of side-effects.

Women tended to lose more weight than men.

Dr Louis Aronne, who conducted the trial at the Comprehensive Weight Control Center at Weill Cornell Medicine in New York, said: “The majority of people with obesity will do just fine with semaglatide (Wegovy), those at the higher end may ultimately do better with tirzepatide (Mounjaro).”