Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
If you’ve been exploring ways to support your weight loss journey, you may have come across injectable options. With obesity affecting 1 in 8 people worldwide, more people are turning to medical interventions for help, especially when diet and exercise alone don’t deliver lasting results.
Among these options, types of weight loss injections are gaining attention for their ability to help manage appetite, regulate blood sugar, and support fat metabolism. In this blog, we’ll walk you through the most common types, how they work, and what to consider before deciding if one might be right for you.
Weight loss injections work in a few different ways, depending on the type. Some mimic hormones that naturally occur in the body to help you feel fuller for longer, while others target how your body burns fat or uses insulin. For example, GLP-1 receptor agonists, originally developed for type 2 diabetes, slow down digestion and reduce appetite, making it easier to eat less without feeling deprived.
Others, like lipotropic injections, contain a mix of vitamins and amino acids that may help your body metabolise fat more efficiently. While these options aren’t magic fixes, they can support your efforts when combined with healthy eating, regular movement, and the guidance of a healthcare professional.
If traditional methods like diet and exercise haven’t worked for you, injectable medications may offer additional support. These treatments are typically prescribed for people with obesity or related conditions and work by targeting hormones that influence appetite, metabolism, or fat breakdown. Below are some of the most common types currently available or emerging in Australia:
These medications mimic a natural hormone that helps regulate appetite and blood sugar. They slow digestion, promote satiety, and are typically prescribed for obesity or type 2 diabetes.
Results from clinical studies published in The New England Journal of Medicine have shown that people using semaglutide lost an average of 15% of their body weight over 68 weeks. These injections are usually taken weekly and may also support heart health.
Want to learn more about how semaglutide works for weight loss? Read our article What Is Semaglutide And How Does It Work for Weight Loss?
Tirzepatide is a newer injectable that targets two hormones, namely, GLP-1 and GIP, to improve appetite control and blood sugar balance. It’s showing strong results for people with obesity, especially those with type 2 diabetes. In a clinical trial, some participants lost more than 20% of their body weight, making tirzepatide one of the most promising treatment options currently available in Australia.
Lipotropic injections combine fat-burning compounds like methionine, inositol, and choline with vitamin B12 to support liver function, metabolism, and energy levels. They're often used alongside weight management programs. While more research is needed, many people report improved energy and moderate fat loss when used as part of a broader healthy lifestyle plan.
Weight loss injections do more than just help shed kilos; they can support overall health in multiple ways. Below are some of the key benefits people may experience.
One of the main benefits of many weight loss injections, particularly GLP-1 receptor agonists, is appetite suppression. These medications help regulate hunger signals by mimicking the hormone that tells your brain you’re full. As a result, people often feel satisfied with smaller portions and are less likely to snack between meals. The clinical research published in The New England Journal of Medicine also found that semaglutide significantly reduced appetite and led to sustained weight loss in participants.
Weight loss injections originally developed for type 2 diabetes, like semaglutide and tirzepatide, help stabilise blood sugar by enhancing insulin sensitivity and slowing glucose absorption. According to research, tirzepatide significantly improved HbA1c levels and supported weight loss more effectively than other treatments. This can be especially helpful for people with insulin resistance or prediabetes. More stable blood sugar levels also reduce cravings and energy dips throughout the day.
Some injections, such as lipotropic formulas, include ingredients that may help the body break down fat more efficiently. These nutrients, like methionine, inositol, and choline, support liver function and fat metabolism. While results can vary, they’re often used as part of a medically supervised program to enhance fat loss.
When paired with improved nutrition and physical activity, weight loss injections may help increase energy levels, especially those that include vitamin B12. B12 plays a key role in converting food into energy and supporting red blood cell production. This boost in energy can make it easier to stay active and motivated. In a randomised clinical trial, 28 days of B-vitamin supplementation, including B12, significantly improved endurance and reduced fatigue in healthy adults, suggesting a potential benefit for physical performance.
By promoting weight loss and improving markers like blood pressure, cholesterol, and insulin levels, these injections may lower the risk of chronic conditions linked to obesity. This includes heart disease, type 2 diabetes, and even some cancers. The SELECT trial shows that semaglutide significantly reduced the risk of major cardiovascular events, such as heart attack and stroke, even in people without diabetes but with obesity and preexisting heart disease. Managing weight through medical support can have a ripple effect on overall health.
Weight loss injections can be a helpful option for some people, but they’re not suitable for everyone. Here’s a quick breakdown of who may benefit and who should avoid them:
Adults with a high BMI (30 or above): Injections may be recommended when lifestyle changes alone aren’t enough to manage obesity.
People with weight-related health issues: Those with conditions like type 2 diabetes, high blood pressure, or sleep apnoea may qualify, even with a BMI of 27 or higher.
Individuals who haven’t seen results with diet and exercise: If you've tried conventional methods without lasting success, injections could be considered as part of a broader medical plan.
Those under medical supervision: Injections should only be used when prescribed and monitored by a qualified healthcare provider.
Pregnant or breastfeeding women: The safety of these treatments during pregnancy or while nursing hasn’t been established.
People with a history of thyroid cancer: Certain medications may increase the risk of thyroid-related complications.
Individuals with severe gastrointestinal disorders: Conditions like gastroparesis may worsen with some weight loss medications.
Those allergic to ingredients in the injection: Allergic reactions can be serious, so ingredient sensitivity must be ruled out.
Anyone not approved by a healthcare provider: Medical assessment is essential to ensure the treatment is appropriate and safe.
Weight loss injections aren’t a one-size-fits-all solution, but for the right person, they can be a powerful tool when combined with healthy habits and medical support. With several types of weight loss injections available, it’s important to understand how they work, what benefits they offer, and whether they’re suitable for your health needs and goals.
As always, speak with a qualified healthcare provider before starting any weight loss treatment. They can help determine if an injection is right for you and ensure it’s part of a safe, long-term plan. Sustainable weight loss is a journey, and finding the right support can make all the difference.
Wondering if weight loss injections are actually safe? Read ‘Are Weight Loss Injections Safe? What You Need to Know Before You Start’ for a science-backed look at the pros, cons and what to consider before starting your injectable journey.
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.