Once-a-week obesity shot 'holds promise for effective weight loss'

Tirzepatide use leads to significant reduction in body weight and improvement in body composition across all BMI categories

The study, although not yet peer reviewed, offers encouraging results. Getty Images

A new obesity treatment that requires just a single injection a week appears to lead to significant weight loss.

In a study presented at the European Congress on Obesity in Dublin, researchers analysed the effect of tirzepatide – produced by Eli Lilly and Company, and marketed under the brand name Mounjaro – on 2,539 adults who were overweight or obese, and who had at least one weight-related complication, excluding diabetes.

The study, although not yet peer reviewed, offers encouraging results.

Participants in the study were divided into groups to receive either a placebo or varying doses of tirzepatide: 5mg, 10mg, or 15mg.

The researchers evaluated the proportion of individuals who lost weight from the start of the study and those who lost more than 5 per cent of their total body weight in various BMI categories.

In addition, body composition was assessed in a smaller group through advanced scans, determining fat mass and lean mass.

Participants at the start of the study had an average weight of more than 104.8kg and a BMI of 38.

At the conclusion of the 72-week study, average body weight loss among the groups taking tirzepatide was 16 per cent for the 5mg dose, 21 per cent for the 10mg dose, and 23 per cent for the 15mg dose.

This was compared with a 2 per cent weight loss for those on the placebo.

An impressive 89 per cent of those on the 5mg dose, 96 per cent on the 10mg, and 96 per cent on the 15mg lost 5 per cent or more of their body weight.

This was a stark contrast to the 28 per cent of participants on the placebo who achieved this level of weight loss.

More than half of those in the 10mg and 15mg groups lost a fifth or more of their body weight, again outpacing the 1 per cent who achieved this on the placebo. All doses of the drug led to weight loss regardless of original BMI.

The researchers also examined a small sub-set of participants to see how much fat they lost compared with non-fat lean body mass.

Their findings revealed that only a quarter of the weight loss was lean mass, indicating an overall improvement in body composition.

Notably, this change was nearly identical across age groups, suggesting no evidence of excess lean mass loss in older individuals.

“In this 72-week trial in participants with obesity, tirzepatide once weekly provided substantial reductions in body weight, consistent across all BMI categories, with improvement in body composition that was clinically meaningful and consistent across age groups,” the authors noted.

Dr Louis Aronne, from Weill Cornell Medicine in New York and a consultant to Eli Lilly, emphasised the significance of understanding the effect of weight loss on fat mass and lean mass, particularly in older people.

He affirmed that approximately three quarters of the weight lost in the study was fat mass, a result consistent across different ages.

It is worth noting that recent research from Eli Lilly demonstrated that tirzepatide also helped people with type 2 diabetes who were overweight or obese lose up to 16 per cent of their body weight over nearly 17 months.

As the obesity epidemic continues to grow worldwide, with the World Health Organisation reporting more than 650 million adults as obese in 2016, breakthroughs in treatment methods such as this are urgently needed.

Obesity has severe health implications, increasing the risk of noncommunicable diseases such as cardiovascular disease, type 2 diabetes, and certain types of cancer.

The potential benefits of tirzepatide, as indicated by this research, could be transformative for millions of people dealing with obesity.

Before this treatment can be widely implemented, however, there are regulatory hurdles to overcome.

The drug, tirzepatide, produced by Eli Lilly and marketed under the brand name Mounjaro, is currently approved by UK regulators for the treatment of type 2 diabetes and is now being considered for obesity treatment.

The National Institute for Health and Care Excellence (Nice) in the UK is currently evaluating whether irzepatide would be a worthwhile use of NHS funds. Once that determination is made, Nice will either recommend or reject the drug's use in the health service.

Nice has already approved a different drug, semaglutide, sold under the brand name Wegovy, for use in the NHS for obesity. If Ttirzepatide gets the nod, it would be another significant tool in the NHS's arsenal against this growing health crisis.