Drugs designed to treat diabetes and repurposed as miracle diet aids have taken over TikTok – and Hollywood.
The weight loss caused by these weekly injectables is rapid and previously unattainable, people boast, showing off newly svelte bodies.
But what are these drugs, how do they work – and what were they originally designed to do?
Ozempic, Wegovy, Mounjaro – what are they?
Let’s start with the most well-known of the trio: Ozempic.
Ozempic blew up in 2022 – if media reports from the US were to be believed, every pound dropped in LA was probably thanks to the “miracle” injectable drug.
What started as the preserve of A-listers and the Hollywood elite quickly grew in popularity.
The drug’s generic name is semaglutide. This is the same as Wegovy, which has been licensed as a weight loss drug in the UK and is now available on the NHS.
Wegovy has a slightly higher dosage and is designed for weight loss, while Ozempic’s primary purpose was as a diabetes treatment (more on that later).
Mounjaro – also known by its generic name tirzepatide – is the newer kid on the block.
Like Ozempic and Wegovy, it suppresses the appetite and lengthens the amount of time food stays in the stomach, leading to weight loss – at least for as long as you carry on taking it.
In 2022, the US Food and Drink Administration (FDA) fast-tracked approval of the drug to treat obesity after a study showed it helped people lose more than 20% of their bodyweight.
Mounjaro was supposed to be available through GP surgeries and other community services in the UK from 23 June.
But at the start of August, Sky News research revealed only eight of 42 NHS Integrated Care Boards (ICBs) in England had started providing treatment to patients, and many of the rest unable to guarantee when it would be available.
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From diabetes drug to diet pill
Ozempic and Mounjaro were both developed as treatments for type 2 diabetes.
The drugs, which come as weekly injections, lower blood sugar by increasing insulin production when your blood sugar is rising and helping prevent your liver making and releasing too much sugar.
So how do they cause weight loss?
Both semaglutide and tirzepatide work by mimicking the hormone, GLP-1 (glucagon-like peptide one), to manage hunger and slow down digestion.
Tirzepatide – Mounjaro – is a dual-acting drug and also mimics the hormone GIP (glucose-dependent insulinotropic polypeptide).
In terms of weight loss, in clinical trials people lost up to 20% of their body weight on tirzepatide and 15% on semaglutide.
Researchers have also found the weight loss jabs could reduce the risk of heart attacks, strokes or heart failure in obese people regardless of the amount of weight they lose.
They sound like miracle drugs for people wanting to lose weight – what’s the catch?
There are a few downsides. First off, the listed side effects: nausea, vomiting and diarrhoea, bad enough for about 5% of people in the semaglutide trial to stop taking it and 6-7% in the tirzepatide trial.
People in the semaglutide trial also experienced problems with gallstones.
The drugs also carry serious risks including kidney failure, pancreatitis and thyroid cancer.
Another downside has been dubbed “Ozempic face”. Facial ageing is a side effect of sudden weight loss as people find the skin on their face sagging where once it was plump.
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Next wave of weight-loss jabs could be coming
The drugs also only work for as long as you carry on taking them, and people have reported gaining back all the weight they lost after stopping the drug – either out of choice or because of a supply shortage.
In August, the National Institute for Health and Care Excellence (NICE) – the body that provides guidance on the use of new drugs – said that people coming off the drugs should be offered “structured advice and follow-up support” to help prevent weight gain.
This includes being monitored by the NHS for at least a year after completing treatment and support to help build “long-term behavioural habits, use self-monitoring tools, and draw on wider support – from online communities to family-led interventions and local activities”.
Shortages for diabetics
Perhaps a bigger conversation than side effects for individuals is around the impact on people who rely on these treatments, now they’ve exploded in popularity as a weight loss quick-fix.
While intended for diabetics, Ozempic and Mounjaro are prescribed “off-label” in the US to people wanting to shed weight.
The drugs faced widespread shortage last year, with reports of diabetics having to drive from pharmacy to pharmacy in search of stock because of the high demand.
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Links to cancer prevention
Research has suggested weight loss jabs, officially GLP-1 receptor agonists, could almost halve the risk of obesity-related cancers.
The study, published in the journal eClinicalMedicine, was presented at the European Congress on Obesity in Malaga.
It found that there were similar rates of obesity-related cancer among patients treated with the injections and those given weight loss, or bariatric, surgery.
Dr Yael Wolff Sagy, the study’s co-lead author from Clalit Health Services in Tel-Aviv, Israel, said a “direct effect” of the injections was that they were found “to be 41% more effective at preventing obesity-related cancer”.
“We do not yet fully understand how GLP-1s work,” she said. “But this study adds to the growing evidence showing that weight loss alone cannot completely account for the metabolic, anti-cancer, and many other benefits that these medications provide.”
Co-lead Professor Dror Dicker, from Hasharon Hospital, Rabin Medical Centre in Israel, suggested the protective effects of the drugs “likely arise from multiple mechanisms, including reducing inflammation”.
He added further research was needed “to make sure that these drugs do not increase the risk for non-obesity-related cancers”.
Being overweight or obese is the second biggest cause of cancer in the UK, causing more than one in 20 cancer cases, according to the NHS.
Are they available in the UK?
An estimated 1.5 million people are taking weight loss jabs in the UK, the vast majority of whom pay for them privately.
Ozempic is available in the UK for type 2 diabetes patients with a prescription.
Wegovy and Mounjaro is available to NHS patients, but only through specialist weight management services.
Over the next three years, around 240,000 people with the “greatest need” are expected to receive Mounjaro through the NHS.
However, Sky News research into Wegovy and Mounjaro shows delays in the rollout of both weight loss jabs.
Last October, there was a two-year waiting list for Wegovy, while Sky News’ Thomas Moore has found that the current rollout of Mounjaro has been mismanaged and underfunded, leading to many people who are eligible to use the jabs unable to access it.
