The continued use of a new obesity treatment can lead to weight loss of up to 23 per cent and a 94 per cent reduction in diabetes after three years, a study involving Irish researchers has found.

The research in The New England Journal of Medicine was carried out on tirzepatide, a new obesity medication, which is taken weekly by injection, and manufactured by the pharmaceutical company Lilly.

“The findings show that weight loss was the same after one and three years, suggesting that continuing medication achieves weight loss stability,” said Irish Society for Clinical Nutrition and Metabolism (IrSPEN) spokesperson Prof Carel le Roux, who is a co-author on the paper.

Prof Carel le Roux

“If 100 people with prediabetes and obesity are treated for three years with the medication, only one will develop diabetes in comparison with 13 patients if they were not treated.

“While weight loss is a marker of the effectiveness of a treatment, the real value for patients are the substantial functional gains (improved quality of life) they achieve because of their weight loss is sustained.

He added: “Patients tell us the biggest benefit is that they can do things again, play with their children or grandchildren and go out with friends.”

Tirzepatide is a GLP-1/GIP agonist – branded as Mounjaro when used as a diabetes medication, and Zepbound when used for obesity treatment. The medication is approved by Ireland’s Health Products Regulatory Authority for the treatment of obesity, but will only be available here in 2025. It has been used to treat patients with obesity in the USA, Europe, and the UK for more than a year.

IrSPEN spokesperson and Bariatric Surgeon Professor Helen Heneghan commented that: “Having more effective treatments for obesity, which can maintain weight loss and health benefits similar to bariatric surgery, can only be helpful to patients with the disease of obesity, especially those that also have the complications of obesity.”

IrSPEN spokesperson and Dietitian Dr Werd Al-Najim said that: “These long-term results are reassuring because there were no new safety concerns, and the medications were well-tolerated. It is especially reassuring that there was no difference in nutritional deficiencies, compared to those treated with the placebo.”

IrSPEN member, GP and specialist in Obesity Management Dr Mick Crotty added that: “Like treatments for other chronic medical conditions, Obesity medications only work while patients take them. Hence, long-term use is required to maintain the health benefits.

“An issue with obesity treatment is that many people do not continue them long-term, this low adherence is affected by many factors including high costs to patients, shortages of the newer medications, side effects and a lack of awareness that Obesity is a medical condition.”

Obesity patient Belinda Hogan concluded: “The HSE should carefully examine the health economic case to allow patients like me with obesity, who also have prediabetes, to have access to new medications which can prevent us from developing diabetes. This may not only help other patients like me but also help the health service if we have fewer patients with diabetes.”