Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
Semaglutide has been making headlines as a breakthrough medication for weight loss. But it wasn’t originally made for shedding kilos. It first entered the scene as a treatment for type 2 diabetes, and researchers soon noticed something else: patients were also losing a significant amount of weight. In clinical trials involving individuals classified as overweight or obese based on their BMI, those who received weekly semaglutide injections lost an average of nearly 15% of their body weight over a 68-week period. Fast forward a few years, and now, semaglutide is being used worldwide to support people struggling with obesity and long-term weight management.
If you're wondering how it works, what it's actually used for, and whether it’s a good fit for you, this guide breaks it all down.
Semaglutide is a medication that acts like a natural hormone in your body called GLP-1. This hormone helps manage things like blood sugar, insulin levels, and your appetite.
Depending on how it’s used, semaglutide goes by different names. If it’s for diabetes, it’s called Ozempic. If it’s for weight loss, you’ll hear it called Wegovy.
So, what does it do? Basically, it helps your body handle food better. It slows down digestion, makes you feel less hungry, and keeps you feeling full for longer, all of which can make it easier to manage your weight.
Semaglutide works by binding to GLP-1 receptors in your brain and pancreas. Here’s what that does:
It tells your pancreas to release insulin when your blood sugar is high
It slows down the movement of food through your stomach
It sends signals to your brain to reduce appetite
In clinical terms, it improves glycaemic control while supporting appetite regulation — two big drivers of long-term weight management.
Below are the key ways it’s currently being used.
Semaglutide helps lower blood glucose levels by increasing insulin secretion and reducing the amount of sugar released by the liver. It’s been shown to significantly reduce HbA1c levels, a marker of long-term blood sugar control.
In trials like STEP 1, participants taking semaglutide lost an average of 14.9% of their body weight over 68 weeks, which is far more than those in the placebo group.
Semaglutide has also been found to lower the risk of major cardiovascular events (like heart attacks or strokes) in people with type 2 diabetes who have established heart disease.
By improving insulin response and reducing glucagon (a hormone that raises blood sugar), semaglutide keeps glucose levels in check, particularly after meals.
One of the most talked-about effects: it curbs cravings by influencing hunger signals in the brain.
Semaglutide delays gastric emptying, meaning food stays in your stomach longer, leading to prolonged fullness and fewer spikes in blood sugar.
Thanks to its unique effects on appetite and metabolism, semaglutide offers several benefits for people looking to lose weight or manage chronic conditions like type 2 diabetes.
Helps with Weight Loss
Clinical trials show that people using semaglutide for weight loss can shed 10–15% of their body weight, depending on dose and duration. It’s a significant amount, especially for those who’ve struggled with traditional diet and exercise plans.
Semaglutide helps bring down both fasting and after-meal blood sugar levels, which makes it easier to avoid those energy dips and keep things more steady throughout the day. One study even showed that people who switched to semaglutide, after other treatments hadn’t done the trick, saw real improvements in both their blood sugar and weight. So if you’ve been struggling to get things under control, this might be a helpful option.
By acting on the appetite centres in your brain, semaglutide helps cut down the urge to snack or overeat. It’s not just theory. Research found that people taking semaglutide had significantly lower food cravings, better control of their eating, and ate much less throughout the day. This means you’re more likely to stick to your meal plan and feel satisfied after eating, without constantly battling your appetite.
According to the SUSTAIN-6 trial, semaglutide lowered the risk of cardiovascular death, heart attack, or stroke by 26% in high-risk patients with type 2 diabetes. That’s a big win for heart health, especially for those already managing chronic conditions.
Semaglutide helps your body respond to insulin more effectively, especially after meals. That means more stable energy and fewer sugar crashes throughout the day. In fact, large clinical trials (like the SUSTAIN 1–3 studies) found that semaglutide significantly improved insulin resistance in people with type 2 diabetes, mostly thanks to the weight loss it helps achieve. It’s a valuable option if you’re dealing with insulin resistance or early-stage type 2 diabetes.
One of the biggest challenges with weight loss is keeping it off, but semaglutide seems to change the game. Instead of just focusing on willpower or restrictive diets, it works with your biology to help maintain progress over time. A major study (the SELECT trial) found that people taking semaglutide not only lost weight but were able to sustain that loss for up to four years. That’s a big deal when it comes to long-term results, especially when paired with healthy lifestyle changes.
Semaglutide works by stimulating GLP-1 receptors in both the brain and gut, which helps you feel full sooner and stay satisfied longer after meals. As a result, you’re likely to experience fewer cravings, less snacking, and a natural reduction in how much you eat throughout the day.
Research into GLP–1–based medications shows they reduce appetite by acting on the central nervous system, leading to meaningful weight loss without the harsh side effects of older weight-loss drugs. It’s a new approach to obesity treatment that works with your biology instead of against it.
Like any medication, semaglutide isn’t without side effects. The most common are related to the digestive system:
Nausea
Vomiting
Diarrhoea
Constipation
Headache
Fatigue
Dizziness
Abdominal pain
Indigestion
Bloating
Belching
Loss of appetite
Injection site reactions
Less common but more serious risks include:
Low blood sugar (especially if taken with other diabetes meds)
Gallbladder problems
Kidney issues
Pancreatitis
Always speak to your doctor if you experience unusual or persistent symptoms.
Semaglutide has been approved for weight loss in:
Adults with a BMI of 30 or higher (classified as obesity)
Adults with a BMI of 27 or higher who also have a weight-related condition like high blood pressure, type 2 diabetes, or high cholesterol
People who have struggled with weight loss through diet and exercise alone
Adults under the supervision of a GP or obesity specialist
It’s not a quick-fix solution, but it can offer real results when paired with long-term lifestyle changes.
Semaglutide is not suitable for everyone. It should be avoided by:
Pregnant or breastfeeding women
People with a history of medullary thyroid carcinoma
Those with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
Individuals allergic to Semaglutide or any of its ingredients
Anyone with a history of pancreatitis
Children and teens under 18
People with severe gut conditions unless medically cleared
Always consult your doctor before starting any new treatment.
Semaglutide works on several pathways in the body to support weight loss.
1. Reduces Appetite: It decreases hunger hormones like ghrelin, so you feel less inclined to snack or overeat.
2. Slows Down Digestion: Food stays in your stomach longer, reducing the urge to eat soon after meals.
3. Increases Feelings of Fullness: It boosts satiety signals to the brain, making you feel full with smaller portions.
4. Lowers Calorie Intake: The combination of reduced hunger and smaller meals naturally cuts your daily intake.
5. Controls Blood Sugar Levels: More stable blood sugar means fewer cravings, especially for high-carb comfort foods.
6. Supports Long-Term Weight Management: By working on the underlying biological drivers of obesity, it offers a long-term strategy, not just a short-term fix.
Some people notice reduced appetite within the first few weeks, while weight loss tends to become more noticeable by week 8 to 12. Clinical trials showed peak weight loss at around 68 weeks, but individual results vary.
Keep in mind: this isn’t an overnight solution. It works best when used consistently, alongside a supportive nutrition and movement plan.
Semaglutide is changing the game for people who’ve been stuck in the cycle of losing and regaining weight. Backed by solid science and used under medical supervision, it offers a new pathway for long-term weight management, especially for those with obesity or related health conditions.
Still, it’s not a magic solution. Like any tool, it works best when paired with meaningful lifestyle changes and personalised support from a healthcare professional.
Thinking about trying semaglutide?
Before you commit, check out this article exploring whether weight loss injections are worthwhile. It breaks down the pros, the cons, and what to consider for long-term success.
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.