Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
So, you’ve heard the buzz about weight loss injections—celebrities are swearing by them, your neighbour’s dropping kilos, and TikTok is flooded with Ozempic glow-ups. It’s easy to feel like you’re the only one not riding the injection train. But before you jump in, let’s get real: are they actually safe?
Weight loss injections like semaglutide (Ozempic, Wegovy) and liraglutide (Saxenda) have made waves for helping people shed significant weight. In fact, clinical trials show people taking semaglutide lost up to 14.9% of their body weight over 68 weeks. That’s more than 15 kg for someone starting at 100 kg. And with 67.9% Australian adults classified as overweight or obese, it’s no wonder these injectables are getting so much attention.
But they’re not a quick fix. These medications were originally developed for type 2 diabetes, and while they’ve been repurposed for weight loss, they come with a long list of side effects and potential health risks. Plus, they’re not suitable for everyone and they certainly shouldn’t be used as a substitute for healthy habits.
The bottom line? Weight loss injections can be safe and effective when used correctly and under proper medical supervision. But they’re not a one-size-fits-all solution. This article unpacks how they work, the different types available, the perks, the pitfalls, and who should or shouldn’t give them a go.
Weight loss injections are medications given via needle (usually under the skin) that are designed to help you lose weight. They might reduce appetite, boost metabolism, improve blood sugar, or do a combo of all three.
These jabs have gained popularity fast. In fact, recent data shows a notable rise in prescriptions for GLP-1 receptor agonists like semaglutide, particularly among adults aged 35 to 60, as more Australians explore medical options for managing obesity.
Most of these injections work by mimicking hormones that regulate appetite and glucose, like GLP-1. This slows stomach emptying, increases the feeling of fullness, and reduces food intake. Some injectables also help with insulin sensitivity and fat metabolism. The result? Weight loss, often with added health perks.
Not all injections are created equal. Some are prescription meds approved by regulatory bodies like the TGA, while others are supplements offered in clinics or medispas.
These GLP-1 receptor agonists were originally designed for type 2 diabetes but have become household names for weight loss. Wegovy is TGA-approved specifically for obesity treatment.
Another GLP-1 agonist that helps reduce appetite. Unlike semaglutide, Saxenda requires daily dosing instead of weekly.
Popular in wellness clinics, these claim to boost energy and metabolism. Evidence for weight loss is limited, but they might help in people with B12 deficiencies.
Based on the pregnancy hormone, HCG injections are controversial and not backed by strong science for weight loss. The TGA and FDA both warn against them.
These contain a mix of vitamins, amino acids, and enzymes said to promote fat breakdown. Like B12 shots, the science is mixed but some users swear by them.
While not miracle cures, weight loss injections can offer real benefits, especially when paired with healthy lifestyle changes.
GLP-1s like semaglutide act on the brain’s hunger centres, making it easier to say no to that second slice of cake.
Clinical trials show semaglutide users lost up to 15% of their body weight over 68 weeks.
These injections are especially helpful for people with insulin resistance or type 2 diabetes.
This can lower your risk of developing diabetes and may help balance hormones in conditions like PCOS.
Some injectables may slightly increase metabolic rate, especially if they include ingredients like MIC or B12.
Losing weight can lower blood pressure and cholesterol, reducing your risk of cardiovascular disease.
Slower stomach emptying means longer lasting fullness. This could also mean fewer calories consumed.
Let’s not sugar-coat it—there are side effects. Most are mild, but some people experience more serious issues.
Nausea
Vomiting
Constipation
Diarrhoea
Headache
Fatigue
Dizziness
Stomach pain
Bloating
Belching
Injection site reactions (like redness or itching)
Here’s where things get a little more serious. Some rare but real risks need to be on your radar.
Pancreatitis: Inflammation of the pancreas, especially in people with a history of it
Gallbladder issues: Gallstones or gallbladder inflammation may occur
Kidney problems: Mainly due to dehydration from vomiting
Low blood sugar: Especially when combined with diabetes meds
Thyroid tumours (rare): Animal studies showed a link; human data is less clear
Dehydration: From prolonged vomiting or diarrhoea
Increased heart rate: Has been noted in some clinical trials
These aren’t for your average ‘I want to lose 5 kilos before my wedding’ crowd. Here’s who they’re typically meant for:
Adults with a BMI of 30 or higher
Adults with a BMI of 27+ and conditions like high blood pressure or diabetes
People with type 2 diabetes struggling with weight
Those who’ve failed to lose weight through diet and exercise
Adults under medical supervision for obesity
People at risk of heart disease due to excess weight
Certain groups should steer clear due to safety concerns or lack of research.
Pregnant women
Women trying to conceive
Breastfeeding mothers
Children and teens under 18
People with a history of thyroid cancer
Individuals with MEN 2 (Multiple Endocrine Neoplasia type 2)
Those with a history of pancreatitis
People allergic to ingredients in the injection
Timing and context matter. These injections are not a first-line solution. They’re usually considered after lifestyle strategies have been tried.
When diet and exercise just aren’t cutting it, injections might help break through a plateau.
If your BMI and health status match clinical guidelines, you might be eligible.
These are prescription-only for a reason and medical oversight is essential.
Ideally, jabs are one part of a broader plan including food, movement and behavioural support.
High blood pressure, high cholesterol or type 2 diabetes may justify injectable options.
Ongoing check-ups help track progress and adjust dosage or switch meds if needed.
Weight loss injections can be a game-changer, but they’re not for everyone, and they’re definitely not a solo act. The best results come when they’re part of a bigger plan that includes medical support, healthy habits and long-term mindset shifts.
Always talk to your GP or a qualified obesity specialist before starting any treatment. And remember: the goal isn’t just to lose weight—it’s to gain health.
Wondering if weight loss injections are really worth it? Before you decide, check out this deep-dive into the pros and cons of weight loss drugs. It unpacks the science, what the research says, and whether they stack up for long-term results.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.