The first head-to-head trial shows Mounjaro helps people lose more weight than its rival Wegovy as scientists confirm why it seems to work better for tackling obesity
The “King Kong” of weight loss jabs has shown to be the best available on the NHS for shedding pounds.
The first head-to-head trial of the injections pitched Mounjaro – which targets a second hormone called GIP to boost its effect on appetite suppression – against the market leader Wegovy. Both are being slowly rolled out on the NHS and over half a million Brits are buying private prescriptions for the weekly jabs.
The new randomised controlled trial involved 751 adults with obesity, but without type 2 diabetes showed the typical drop in body weight at the end of the trial was a 20.2% reduction with Mounjaro and 13.7% with Wegovy.
Most weight loss jabs mimic the glucagon-like peptide 1 (GLP-1) hormone which regulates feelings of fullness. Mounjaro, also known as tirzepatide, also targets a hormone called GIP to boost its effect on appetite suppression.
Dr Louis Aronne, from Weill Cornell Medicine in New York, who led the work, said: “Our study shows that treatment with tirzepatide was superior to semaglutide with respect to reduction in body weight and waist circumference.
“Tirzepatide, while a single molecule, pharmacologically activates two metabolic receptors, GIP and GLP-1, which have both overlapping and non-overlapping expression and function. This dual agonism of tirzepatide may contribute to the higher weight reduction.”
The study also showed the drop in waist circumference was 18.4cm on average with Mounjaro compared to 13cm with Wegovy. People on Mounjaro were more likely to reach their weight loss goals. The trial also confirmed women lose more weight on the jabs than men as a percentage of their body weight.
High demand means the health service has announced a phased rollout of Mounjaro, also known by its proper name tirzepatide, after it was approved for obesity as well as type 2 diabetes last year. Plans are in place to roll it out to a quarter of a million people on the NHS, starting with the more seriously obese and unwell.
The two biggest selling weight loss jabs are branded as Wegovy or Ozempic which are both the same drug semaglutide but sold at different doses. Ozempis is prescribed by the NHS only for Type 2 diabetes. Semaglutide was originally designed to tackle Type 2 diabetes but was repurposed for obesity and trials showed its stronger dose form, branded as Wegovy, could help users lose 15% of their body weight in 68 weeks.
Semaglutide drugs, manufactured by Novo Nordisk, became popular globally after celebrities including Sharon Osbourne, Elon Musk and even ex-PM Boris Johnson boasted about trying them for weight loss.
After them came Mounjaro which, as well as mimicking GLP-1, also targeted a hormone called GIP to boost its effect on appetite suppression. Trials showed it could help obese people lose 21% of their body weight in 72 weeks.
One problem with the injections stems from the fact that users lose muscle as well as fat. Without personalised lifestyle support from specialists, users often fail to make the dramatic diet and lifestyle changes necessary to sustain the weight loss. This means they can put the fat back on but not the muscle.