Fat-reducing injections have aided millions in shedding excess pounds, thanks to their dual action: targeting the gut and quieting the constant “food noise” that often leads to overeating.

Researchers have now unveiled the mechanism behind this noise-silencing effect in the brain, a discovery that could pave the way for these medications to address other issues, such as pain management.

Known as GLP-1 agonists, these weight loss injections are used by approximately 2.5 million people in the UK. They mimic a naturally occurring hormone, glucagon-like peptide-1, which is released after eating.

Administered once a week, these injections slow gastric emptying, promoting a feeling of fullness that lasts longer.

Recent findings reveal that the GLP-1 agonist tirzepatide, marketed as Mounjaro, may influence brain waves in a previously unrecognized way, contributing to the reduction of “food noise.” Many users report a significant decrease in food-related thoughts.

Food noise is a widespread issue, affecting about 60% of those with obesity, as highlighted in a U.S. survey of individuals using semaglutide for weight management. These findings were shared at the European Association for the Study of Diabetes conference last year.

As well as binges, food noise is a factor with anorexia – where people restrict their food intake and have a fear of gaining weight – as it causes those affected to feel preoccupied by food or dieting. 

However, researchers have now discovered that Mounjaro appears to slow brain waves, known as delta-theta oscillations, that trigger food noise.

Researchers have discovered Mounjaro appears to slow brain waves that trigger food noise

Dr Simon Cork, of Anglia Ruskin University, said the results were ‘very interesting’

Previous research, published in Nature Medicine in 2022, found there is a distinctive rise in low-frequency electrical activity in the nucleus accumbens – an area of the brain that helps regulate motivation, pleasure and impulse control – just before someone experiences the urge to binge, but not when they are simply hungry.

Researchers had been looking at whether electrical stimulation (via electrodes implanted in the brain) could help reduce the overactive brain waves and so cut the urge to binge-eat in people with treatment-resistant obesity.

This kind of stimulation is already used to treat drug-resistant epilepsy and Parkinson’s with some success.

But now researchers at the University of Pennsylvania have found that taking Mounjaro seems to offer a simpler approach, and stops these brain waves from intensifying – for months on end.

Three patients with severe food noise (who had not found relief through gastric-bypass surgery, behavioural therapy or standard medications) had brain implants surgically put into the nucleus accumbens.

They were asked to swipe a device over the area when they felt the urge to eat, which prompted the implant to record the brain signals.

The participants also swiped when they had no desire to eat. Only one of the three was taking Mounjaro – a 60-year-old woman.  

For the other two, the electrodes recorded significant increases in delta-theta waves every time they experienced food noise.

However, the woman taking Mounjaro reported almost no episodes of food noise and the brain waves did not power up.

After about five months, the volunteer had stronger delta-theta waves and increased food noise, suggesting that Mounjaro only has a temporary impact.

The study, published in Nature Medicine in November, is one of the first in-human trials to investigate Mounjaro’s effect on the brain – and could help guide binge-eating research.

It may have other applications too, as the same brain waves that stimulate food noise are also implicated in chronic pain and more.

Developing ways to treat food noise ‘is of utmost importance’, said Casey Halpern, a professor of neurosurgery at the University of Pennsylvania, who led the new study.

While emphasising the need for further research, he believes the finding may lead to other uses for Mounjaro – which could mean no need for any surgical intervention if it can be modified to last longer.

Dr Simon Cork, a senior lecturer in physiology at Anglia Ruskin University, said the results are ‘very interesting’, but should be viewed with caution as ‘this is only one patient with a specific condition that is associated with obesity and so shouldn’t be generalised to the entire population’.

Tom Quinn, director of external affairs at Beat, an eating disorder charity, adds that ‘this study has shown positive results for a participant with binge-eating disorder, but more research is needed.

‘At the moment we’re particularly concerned about what happens when someone stops taking these drugs, as their eating disorder symptoms may reappear or worsen.’

Other ways of calming overactive brain waves linked to conditions such as chronic pain are being investigated.

For example, researchers at the University of South Wales in Australia have developed PainWaive, an interactive game with a headset. 

The headset ‘reads’ the brain waves and alters the game to calm brain waves associated with chronic pain. Early results, published in the Journal of Pain last year, were promising.

Manipulating brain waves is also being investigated for Alzheimer’s. Scientists at Massachusetts Institute of Technology in the US have been exploring whether altering gamma brain waves had memory benefits.

Their device comprises special glasses and headphones which emit lights and sounds designed to stimulate longer-wave gamma oscillations – exposure to which can improve memory – compared to controls. Larger trials are under way.