Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
If you’ve been scrolling through health news or TikTok lately, you’ve probably seen the hype around semaglutides, the so-called ‘game-changing’ weight loss injections and tablets. But here’s the thing: they’re not just hype. Backed by serious clinical research, semaglutides are proving to be one of the most effective medical treatments for weight management today.
In Australia, nearly 2 in 3 adults (66%) are overweight or obese, according to the Australian Institute of Health and Welfare. At the same time, research shows that people taking semaglutide lost an average of 14.9% of their body weight in 68 weeks, compared to only 2.4% in the placebo group. That’s not just a small difference; it’s life-changing for many.
Semaglutide is part of a group of medications called GLP-1 receptor agonists. In simple terms, it mimics a natural hormone called glucagon-like peptide-1 (GLP-1), which helps regulate appetite, digestion, and blood sugar.
When taken, semaglutide binds to GLP-1 receptors in the pancreas, gut, and brain. This stimulates insulin release when blood sugar levels are high, slows down how quickly food leaves the stomach, and sends satiety signals to the brain, all of which work together to reduce hunger and stabilise energy levels.
According to research, semaglutide significantly enhances insulin secretion and lowers glucagon release in people with type 2 diabetes. Another study highlighted how GLP-1 receptor activation in the brain’s appetite-regulating centres directly reduces food intake, which explains why people naturally feel fuller on smaller meals.
First approved as a diabetes treatment in 2017, semaglutide later gained approval in 2021 and 2022 for higher-dose use in weight management. Today, it’s available in different forms, injections or tablets, depending on individual needs. Here’s how each one works:
Ozempic is mainly prescribed for type 2 diabetes but is also widely used off-label for weight loss. It comes as a once-weekly injection and helps lower blood sugar while also reducing appetite. Many patients find it easier to stick to because of its simple weekly dosing compared to daily medications.
Wegovy is specifically approved for weight management in people with obesity or overweight conditions. It’s also a once-weekly injection, but at higher doses than Ozempic to target weight loss more directly. Clinical trials demonstrate that it not only helps reduce body weight but also improves cardiometabolic health, making it a strong choice for long-term treatment.
Prefer pills over needles? Rybelsus is the oral form of semaglutide. It’s taken daily and is especially useful for people who prefer not to inject. While it may be less potent for weight loss than the injectable forms, studies show it still provides significant improvements in blood sugar control and appetite regulation.
Semaglutide helps with weight loss in more than one way. Let’s break it down:
One of the biggest hurdles to weight loss is constant hunger. Semaglutide works by targeting areas in the brain that regulate appetite, making you feel satisfied with smaller meals.
In a randomised, placebo-controlled trial, once-weekly semaglutide led to lower overall hunger scores, less craving, and better control over eating, especially reducing the desire for fatty and energy-dense foods.
When food leaves the stomach more slowly, you stay fuller for longer. Semaglutide delays stomach emptying, which can reduce overall calorie intake throughout the day.
In women with obesity and polycystic ovary syndrome (PCOS), semaglutide weekly injections increased gastric content retention markedly at 2-, 3-, and 4-hour marks compared to placebo, and lengthened the half-emptying time from about 118 minutes to 171 minutes. This delayed emptying also contributes to the sensation of fullness and slows the post-meal blood glucose rise, making you less likely to reach for a snack soon after eating.
Better insulin response means more stable blood sugar levels. This not only helps with type 2 diabetes management but also prevents sudden spikes and crashes that can trigger overeating.
Studies of GLP-1 receptor agonists like semaglutide show that they promote glucose-dependent insulin secretion and reduce glucagon release, improving glucose homeostasis and reducing stress on pancreatic β-cells. Also, by stabilising blood sugar, semaglutide helps reduce insulin resistance, which is often present in overweight individuals. This improved sensitivity helps the body use glucose more effectively, reducing fat storage.
Ever notice how hard it is to resist chips or chocolate when cravings hit? Studies suggest semaglutide reduces the brain’s reward response to high-fat and high-sugar foods, making them easier to skip. In one trial, people on semaglutide showed significantly reduced preference and liking for fatty foods, and this change was measurable both in reported food choice and in actual energy intake.
With reduced hunger and cravings, controlling portion sizes becomes easier. Many users report naturally eating less without feeling deprived, which is key for long-term weight loss.
Semaglutide trials have shown that, during ad libitum (eat what you want) meals, participants on treatment consumed significantly fewer kilojoules/calories across lunch, dinner, and snacks compared to placebo. Additionally, improved satiety from slower digestion and brain signalling helps people feel full sooner, which supports smaller portion norms and makes dietary adherence much more sustainable.
How you use semaglutide matters just as much as the dose. These clinical guidelines emphasise proper injection technique, site rotation, and timing for oral tablets to maximise effectiveness and reduce side effects.
Always start under medical supervision. Dosage is usually increased gradually to minimise side effects.
Inject once a week on the same day each week
Use recommended areas: abdomen, thigh, or upper arm
Rotate injection sites to avoid irritation
Never share your pen with anyone else
Take once daily in the morning with a small sip of plain water
Wait at least 30 minutes before eating, drinking, or taking other medication
Swallow whole. Do not split or crush
Unopened pens: refrigerate (2°C to 8°C)
Opened pens: store at room temperature (up to 30°C) for 56 days
Tablets: keep at room temperature away from heat and moisture
Not everyone is suited to this type of treatment. Doctors usually recommend it for adults who meet certain health and weight criteria, after a careful medical assessment.
Adults with type 2 diabetes
Adults with obesity (BMI 30 or higher)
Adults who are overweight (BMI 27 or higher) with weight-related conditions
Anyone approved by a healthcare provider after full evaluation
Results don’t happen overnight, but research shows a clear pattern:
First few weeks: Appetite suppression and reduced energy intake are measurable early on, as shown in mechanistic and ad-libitum meal trials. This is often when people first notice feeling less hungry.
3–6 months: Weight loss continues, averaging 10–11% at 6 months with weekly injections. Many also see better blood sugar and blood pressure control.
Around 1 year: Long-term trials report up to 15% average weight loss at 68 weeks, especially when paired with diet and exercise changes.
After 1 year: Some people plateau, but research shows weight loss can be sustained for several years, even up to 4 years, with continued use. If you’re wondering what happens after this point, including how long treatment is usually continued, we’ve covered it in detail in our article How Long Do You Stay On Weight Loss Injections? Things You Should Know First.
Like many medications, semaglutide can cause side effects, especially in the early weeks or during dose increases. Most are mild to moderate and often improve over time.
Nausea: The most common side effect, usually mild, as your stomach adjusts to slower emptying.
Vomiting: Less frequent than nausea but may happen when the dose is increased.
Diarrhoea: Loose stools are fairly common but often settle within a few weeks.
Constipation: Some people experience the opposite—slower bowel movements or harder stools.
Abdominal pain: Cramping or discomfort can occur as digestion slows down.
Headache: Reported by some users, possibly linked to changes in blood sugar levels.
Fatigue: Tiredness may occur, particularly in the first few weeks of treatment.
Dizziness: Some patients report feeling lightheaded, especially early in treatment.
Bloating: A feeling of fullness or gas can happen as food stays in the stomach longer.
Most of these side effects ease as your body adapts, but it’s important to talk to your doctor if they persist or become severe.
So, how do semaglutides help you lose weight? By reducing appetite, slowing digestion, curbing cravings, and supporting portion control, all while improving blood sugar balance. Backed by strong clinical research, they’re a promising option for people struggling with obesity or type 2 diabetes.
That said, semaglutides aren’t a magic bullet. They work best alongside healthy eating, exercise, and medical guidance. If you think semaglutide could be right for you, have a chat with your doctor to find the safest, most effective path forward.
Want to know how semaglutide can help you lose weight even if you don’t have diabetes? Read this clear explainer on how semaglutide reduces appetite, slows stomach emptying and supports sustainable weight loss.
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.