A new obesity drug, which has been found to reduce body weight by three to four stone (19-38kg), has been approved for use in Ireland.

The European Medicines Agency said the new drug - Wegovy - has been approved for patient use in all EU countries, for adults with obesity who have at least one weight-related health issue.

The drug is administered through weekly injections.

Clinical trials found that Wegovy was found to affect weight loss of 17% in patients who took it every week for a year.

However, the weight loss was only sustained if the drug is continued long-term.

In a statement, Obesity Specialist at St Vincent's University Hospital Professor Carel le Roux said that the approval of Wegovy provides great promise for people with obesity.

"The unprecedented level of weight loss this medication achieves marks a new era in the treatment of this disease.

"Wegovy may be a foundation drug that can revolutionise the management of obesity.

"The drug was found to be safe and well-tolerated during trials, with the most common side effects including mild to moderate gastrointestinal upset."

Obesity affects more than one million people in Ireland and is a contributing factor to Type 2 diabetes, which affects around 200,000 people.

Prof Le Roux said there has been a ten-fold increase in the uptake of the drug in the US because it is so effective and easy to use with very few side effects.

He said the drug may not work for people who have what is termed a "cultural desire for thinness" because it works really only for people with the disease of obesity.

Speaking on RTÉ's Today with Claire Byrne, he said it is not a weight loss drug but rather a "health gain" drug.

"This is biology and really gets us away from this idea that obesity is the fault of an individual.

"Rather, it's not their fault, but it is our responsibility as healthcare professionals and the patient's responsibility to find a treatment that really works.

"Obesity is a chronic disease, and we can tell that in three months if we start this medication and patients come back and they say, look, I'm not feeling hungry, I'm feeling satisfied, I'm eating the same food I've always eaten I just eat less of it, and I've lost a lot of weight. Then we know the medication is working."

It is a drug that must be taken for life, so if someone does take it to lose a small amount of weight, they will likely gain back the weight and more when they stop taking it, Prof Le Roux said.

The drug is "very expensive", he said, but authorities all over the world are working to get the costs reduced.