What are weight-loss injections and who can use them?

Doctors explain how weight-loss injections work. By Lisa Salmon.

TWTJ9D Male on weight scale on floor background, Diet concept.
TWTJ9D Male on weight scale on floor background, Diet concept.

Appetite suppressing drugs are increasingly becoming a hot topic of conversation.

Weight-loss injections, like Wegovy and Saxenda, are available on the NHS, and if they are prescribed alongside a reduced-calorie diet, increased physical activity, and behavioural support, after a year people taking them can lose more than 10% of their body weight, according to the National Institute for Health and Care Excellence (Nice).

The Ozempic drug, however, can only be prescribed for patients with type 2 diabetes, and isn’t licensed as a weight-loss drug in the UK or the US, although the UK government acknowledges: “It is not authorised for weight-loss, but it is used off-label for that purpose.”

Dr Alexis Missick from the online pharmacy UK Meds says there are ongoing discussions about the appropriateness and safety of using a drug intended for type 2 diabetes for an off-label purpose, and warns: “Medical experts caution against the casual use of such medications without a proper understanding of their effects and potential risks. While Ozempic has shown effectiveness in weight-loss, primarily due to its appetite-suppressing properties, it also carries risks including, but not limited to, potential gastrointestinal side-effects.

“It’s crucial to approach Ozempic with a comprehensive understanding of its potential side-effects and to use it under strict medical supervision and guidance.”

But what about the weight-loss injections that are licensed in the UK, like Wegovy and Saxenda, and the more recently approved Mounjaro?

How do the injections work?

Dr Babak Ashrafi from Superdrug Online Doctor explains that a hormone called GLP-1 is released by the guts when we eat, and weight-loss injections are what’s called ‘GLP-1 analogues’ which mimic the hormone.

“GLP-1 is a hormone produced in the small and large intestines, and it plays a crucial role in regulating blood sugar levels by stimulating  the release of insulin from the pancreas,” he says. “Additionally, GLP-1 slows down gastric emptying and signals satiety to the brain, which contributes to a feeling of fullness and satisfaction after eating.

“Synthetic analogues of GLP-1 replicate the effects of the natural hormone telling your brain you are full and satisfied.”

 Who can benefit from weight-loss injections?

Nice has issued guidance for semaglutide injections like Wegovy recommending them for adults with at least one weight-related condition and a body mass index (BMI) of at least 35. In some cases, those with a BMI of 30 may be able to access the injections.

“They are typically recommended for people who have not achieved sufficient weight-loss through diet and exercise alone, with the aim of improving their overall health and quality of life” says Ashrafi.

(Alamy Stock Photo)

How long do you take the injections for?

This  varies from person to person, but the Nice guidelines say semaglutide should be used for a maximum of two years.

“It is typical to start seeing significant changes in your weight within the first six months,” says Ashrafi.”If you haven’t achieved a weight-loss of five to 10% by that time – a goal that most patients in the studies have reached – then this medication might not be suitable for you. It’s advisable to discontinue it and explore alternative treatment options.”

According to Nice, people on the weekly injections saw their weight drop by 12% on average after 68 weeks.

What are the side-effects?

Because the drug acts on the gut, side-effects can include nausea, heartburn and constipation, although Ashrafi says these do tend to get better with time and hydration.

“It is common for people to unintentionally reduce their daily fluid intake as a result of having a reduced appetite. This can result in feeling bloating, irregular bowel movements and stomach irritation,” he explains.

In addition, there may be brain-related side effects like headaches and fatigue, and Ashrafi warns: “This is due to their impact on central nervous system receptors. Fluctuations in blood sugar levels resulting from changes to insulin and glucagon levels may also contribute to these symptoms.

“Eating small nutritious meals regularly instead of larger meals three times a day is a great way to combat this.”

Anything else you need to know?

At the beginning of March, it was announced that semaglutide, also known as Wegovy, was to be made available on prescription through the NHS.

The drug is an appetite suppressant which is delivered via a weekly injection.

This news prompted reaction from academics and charities, with Dr Stephen Lawrence, associate clinical professor at the University of Warwick, warning previously that the medication is “not a quick fix or a replacement for following a healthy lifestyle, which includes regular physical activity and healthy eating”.

Eating disorder charity Beat also raised concerns about Wegovy.

However, Alex Miras, professor of endocrinology at Ulster University, hailed the decision by Nice as “a pivotal moment for the treatment of people living with obesity”.