Weight-Loss Medicines: Who They Help, Who They Don’t and What to Expect

A practical guide to deciding whether weight-loss medication is appropriate, what results to expect and why treatment needs to be about more than the number on the scales

Weight-loss medicines have changed the conversation around obesity.

For some people, medicines such as semaglutide or tirzepatide can produce substantial weight loss and improve obesity-related health problems.

But these medicines are not simply:

“injections for anyone who wants to lose a few kilos.”

The better question is:

“Would losing weight with medication meaningfully improve my health, and is this the right treatment for me?”

That means considering:

• your current weight and waist;
• medical conditions;
• previous weight-loss attempts;
• eating patterns;
• sleep;
• physical activity;
• medicines;
• pregnancy plans;
• side effects;
• cost;
• what may happen if treatment stops.

The scale matters.

But it is not the whole story.

Who are weight-loss medicines generally for?

Medication may be considered for adults living with:

• obesity — generally a BMI of 30 kg/m² or higher; or
• overweight — generally a BMI of 27 kg/m² or higher with at least one weight-related health complication.

Examples of weight-related conditions include:

• type 2 diabetes;
• high blood pressure;
• abnormal cholesterol;
• metabolic fatty liver disease;
• obstructive sleep apnoea;
• osteoarthritis.

BMI is only one part of the decision.

It does not directly measure body fat, fitness or metabolic health, and it should not replace clinical judgement.

What are we actually trying to improve?

Weight loss is useful when it improves health.

Possible goals include:

• lowering blood pressure;
• improving blood sugar;
• reducing diabetes risk;
• improving sleep apnoea;
• reducing fatty liver disease;
• reducing joint symptoms;
• improving mobility;
• making exercise easier;
• reducing cardiovascular risk;
• improving quality of life.

Even 5–15% weight loss can produce meaningful health improvements, depending on the person and their medical conditions.

So treatment should not be judged only by:

“Have I reached my ideal weight?”

A better question is:

“What has become healthier or easier because of the weight loss?”

What medicines are available?

Several types of medicines are used for chronic weight management in Australia.

These include:

GLP-1 based medicines

• semaglutide — Wegovy for chronic weight management;
• liraglutide — Saxenda for chronic weight management.

Dual GIP/GLP-1 medicine

• tirzepatide — Mounjaro, approved for chronic weight management as well as type 2 diabetes.

Other medicines

Other weight-loss medicines include:

• phentermine;
• naltrexone/bupropion;
• orlistat.

They work differently and suit different people.

Q Guide GLP-1 Weight-Loss Medicines: Benefits, Side Effects and Long-Term Use looks specifically at GLP-1 and GIP/GLP-1 medicines in more detail.

Ozempic versus Wegovy: aren’t they both semaglutide?

Yes.

They contain the same active ingredient.

But their approved indications are different.

In Australia:

• Ozempic is approved for type 2 diabetes;
• Wegovy is approved for chronic weight management.

That distinction matters.

A medicine having the same active ingredient does not mean every brand has the same approved use, dose schedule or PBS eligibility.

How do the newer injections work?

GLP-1 based medicines mimic hormones involved in appetite and digestion.

They can:

• reduce hunger;
• increase fullness;
• reduce how much food feels necessary;
• slow stomach emptying.

Tirzepatide acts on both GIP and GLP-1 pathways.

For many people, one of the most striking changes is not:

“I suddenly have more willpower.”

It is:

“I am thinking about food less.”

That can make a sustained calorie deficit much easier to achieve.

How much weight can people lose?

It varies.

The newer incretin-based medicines can produce substantial average weight loss.

In clinical trials, semaglutide has commonly produced average losses around the 10–15% range, while tirzepatide trials have reported average losses around 15–20% or more at higher doses in selected participants.

But averages are not promises.

Some people lose substantially more.

Some lose much less.

Some cannot tolerate the medicine.

Some stop because of cost.

The goal is not to chase somebody else’s percentage from social media.

Does more weight loss always mean better treatment?

No.

A person losing weight rapidly but also:

• eating very little protein;
• losing strength;
• becoming dehydrated;
• feeling constantly nauseated;
• becoming nutritionally depleted

does not necessarily have a good treatment outcome.

Treatment quality matters.

The aim is fat loss while preserving health and function.

What about muscle loss?

Any substantial weight loss can include some loss of lean tissue as well as fat.

That is one reason weight-loss treatment should include:

• adequate protein;
• resistance exercise where possible;
• regular physical activity;
• avoiding unnecessarily severe calorie restriction.

For older adults in particular, simply becoming lighter while becoming weaker is not the goal.

Are weight-loss medicines just replacing diet and exercise?

No.

But they can change what lifestyle treatment can realistically achieve.

Weight is influenced by:

• genetics;
• appetite biology;
• sleep;
• environment;
• medicines;
• mental health;
• food availability;
• physical activity;
• social factors.

After weight loss, the body can respond in ways that encourage weight regain.

Medication does not make food quality, activity and sleep irrelevant.

It can make healthier behaviours easier to sustain.

What should I do while taking medication?

Think beyond the scale.

Protect muscle

Include adequate protein and regular resistance exercise where practical.

Eat for health

Aim for:

• vegetables;
• fruit;
• legumes;
• whole grains;
• lean proteins;
• healthy fats.

Weight-loss medication is not a licence to live on tiny portions of nutritionally poor food.

Keep moving

Physical activity helps with:

• cardiovascular fitness;
• muscle;
• bone health;
• mood;
• maintaining weight loss.

Sleep

Poor sleep can increase hunger and make weight management harder.

Review other health risks

This is a good opportunity to check:

• blood pressure;
• cholesterol;
• diabetes risk;
• liver health;
• sleep apnoea;
• smoking;
• alcohol;
• cancer screening.

Weight loss should be part of a wider health plan.

What side effects should I expect?

That depends on the medicine.

With GLP-1 and GIP/GLP-1 medicines, the most common problems are gastrointestinal.

These can include:

• nausea;
• vomiting;
• bloating;
• constipation;
• diarrhoea;
• reflux;
• abdominal discomfort.

These effects are often most noticeable:

• when treatment starts;
• after a dose increase;
• after large or rich meals.

Dose escalation is gradual partly to improve tolerability.

What symptoms need medical review?

Seek medical advice if you develop significant or persistent:

• vomiting;
• dehydration;
• severe abdominal pain;
• inability to eat or drink adequately;
• marked constipation;
• unusual mood change.

Serious complications are uncommon, but severe symptoms should not simply be dismissed as:

“normal because I’m on a weight-loss injection.”

What about the newer eye warning?

In July 2026, the TGA updated warnings for GLP-1 medicines regarding a rare eye condition called non-arteritic anterior ischaemic optic neuropathy, or NAION.

The overall risk appears low.

But if you develop sudden partial or complete loss of vision, seek urgent medical assessment.

Q Guide GLP-1 Weight-Loss Medicines: Benefits, Side Effects and Long-Term Use discusses GLP-1 safety in more detail.

What about mood changes?

Australian product warnings also advise patients to report:

• new or worsening depression;
• suicidal thoughts;
• unusual mood or behavioural changes.

This does not mean these medicines commonly cause suicidal behaviour.

It means concerning changes in mood deserve review rather than being ignored.

What if I need surgery or anaesthesia?

Tell the surgical or anaesthetic team if you take a GLP-1 or GIP/GLP-1 medicine.

These medicines can slow stomach emptying, which may affect aspiration risk during general anaesthesia or deep sedation.

Do not invent your own pre-operative dosing plan.

Follow the instructions from your treating and anaesthetic team.

Pregnancy and weight-loss medicines

Weight-loss pharmacotherapy is not used during pregnancy.

GLP-1 based medicines are not recommended during pregnancy.

Tirzepatide deserves an additional warning.

People using oral contraception are advised to switch to a non-oral method or add a barrier method for:

• 4 weeks after starting tirzepatide; and
• 4 weeks after each dose increase.

If pregnancy is planned, discuss the medicine well in advance with your prescriber.

Who may not be suitable for these medicines?

The answer depends on the specific drug.

Reasons to avoid or reconsider a particular medicine may include:

• pregnancy or breastfeeding;
• important gastrointestinal disease;
• previous serious drug reactions;
• certain endocrine conditions;
• particular cardiovascular risks;
• some psychiatric conditions;
• significant medication interactions;
• disordered eating;
• inability to maintain adequate nutrition;
• planned pregnancy.

This is why prescribing should follow an actual medical assessment rather than simply selecting a medicine from an online list.

What if I only want to lose 5 kg?

That alone does not automatically justify medication.

The key questions are:

• What is your BMI and waist?
• Is excess weight affecting your health?
• Are there weight-related complications?
• What approaches have already been tried?
• What are the likely benefits?
• What are the risks and costs?

Weight-loss medication is intended to treat overweight or obesity where there is a meaningful health indication, not simply dissatisfaction with normal body size.

What about someone with an eating disorder?

This deserves careful assessment.

Weight-loss medicines may be inappropriate or potentially harmful in someone with:

• active anorexia nervosa;
• bulimia;
• significant restrictive eating;
• uncontrolled binge-eating symptoms;
• severe body-image disturbance.

Obesity treatment and eating-disorder treatment can overlap in complex ways.

If the eating pattern is concerning, it should be assessed rather than ignored because the person’s BMI is high.

Do I need the highest dose?

No.

The goal is not automatically to reach the maximum dose.

Dose decisions should consider:

• weight response;
• side effects;
• appetite;
• nutritional intake;
• other health benefits;
• cost.

Some people do well at a lower dose.

Others require escalation.

The right dose is the one that gives a useful balance of benefit, tolerability and sustainability.

What if the medicine seems to stop working?

Weight loss normally slows over time.

That does not necessarily mean the medicine has suddenly failed.

As body weight falls:

• energy requirements decrease;
• appetite biology adapts;
• the initial rapid phase usually slows.

The important questions become:

• Has weight moved meaningfully?
• Have health markers improved?
• Is the dose appropriate?
• Are nutrition and activity still sensible?

Sometimes treatment needs reassessment rather than automatic dose escalation.

What happens if I stop?

This is one of the most important discussions to have before starting.

Weight regain is common after obesity medicines are stopped.

That does not mean everyone must stay on the same medicine forever.

But it does mean:

“I’ll use it for three months, lose the weight and then everything will stay the same”

may be unrealistic.

Obesity is often a chronic relapsing condition, not a temporary failure of discipline.

Does that mean lifelong treatment?

Sometimes long-term treatment may be appropriate.

Others may:

• reduce the dose;
• change medicines;
• stop with close follow-up;
• maintain some of the weight loss through intensive lifestyle measures.

The plan should be individualised.

The important point is to have a maintenance strategy, not just a weight-loss strategy.

What if cost becomes the main problem?

That is very relevant in Australia.

As of August 2026, medicines prescribed specifically for chronic weight management are generally not broadly PBS subsidised.

The PBAC has recommended PBS listing of Wegovy for a narrower group of people with established cardiovascular disease and obesity, but further implementation steps are still required before subsidy begins.

Broader obesity treatment therefore remains largely a private cost.

That matters.

A medicine that works very well but is financially impossible to continue may not be a sustainable plan.

Can the medicines improve more than weight?

Yes.

Selected incretin medicines have demonstrated benefits beyond weight loss, including:

• improved diabetes control;
• in specific populations, improved cardiovascular outcomes;
• improved obstructive sleep apnoea;
• benefits in metabolic fatty liver disease;
• benefits in obesity-related heart failure.

Tirzepatide is also approved in Australia for moderate-to-severe obstructive sleep apnoea in adults with obesity.

These benefits depend on the specific medicine and the specific patient population.

They should not be interpreted as every drug treating every obesity-related disease.

Q Guide GLP-1 Weight-Loss Medicines: Benefits, Side Effects and Long-Term Use looks more closely at the evidence beyond the scale.

What should my GP assess before treatment?

A useful weight-management consultation should look beyond BMI.

I would usually want to consider:

• weight and waist trend;
• blood pressure;
• diabetes or prediabetes;
• cholesterol;
• liver health;
• sleep apnoea;
• cardiovascular disease;
• current medicines;
• alcohol;
• eating pattern;
• mental health;
• pregnancy plans;
• previous weight-loss attempts.

It may also be useful to ask:

“What is the health problem we are actually trying to improve?”

That helps avoid treatment becoming purely cosmetic.

What should be monitored?

Depending on treatment and medical history, follow-up may include:

• weight;
• waist;
• blood pressure;
• side effects;
• nutrition;
• strength and activity;
• blood sugar;
• mood;
• whether the treatment remains affordable.

In people with diabetes or hypertension, successful weight loss may eventually mean existing medicines need adjustment.

That is another reason follow-up matters.

A common misconception

MYTH: Taking weight-loss medication is cheating.

REALITY: Obesity is influenced by powerful biological and environmental factors.

Medication does not remove the need for healthy behaviours.

It can make those behaviours much more achievable.

We do not describe blood-pressure medication as cheating.

Weight treatment should be judged by whether it improves health safely.

Another common misconception

MYTH: If the medicine works, I can eat whatever I want.

REALITY: The medicine may reduce appetite, but food quality still matters.

Eating too little protein, relying on highly processed food or becoming progressively weaker is not a good treatment outcome simply because the number on the scale is falling.

And another

MYTH: Once I reach my goal weight, I can stop and the weight will stay off automatically.

REALITY: Weight regain after stopping medication is common.

Long-term maintenance needs its own plan.

That plan may include:

• ongoing medication;
• adjusted medication;
• structured eating;
• physical activity;
• resistance training;
• regular follow-up.

The question I would ask

Before prescribing, I would ask:

“If this medicine works, what do you hope will actually be better in your life?”

Maybe the answer is:

• my diabetes;
• my blood pressure;
• my sleep apnoea;
• my knees;
• my ability to exercise;
• my energy;
• my cardiovascular risk.

That gives us a better treatment goal than simply:

“I want the number on the scales to be lower.”

The bottom line

Weight-loss medicines can be powerful tools.

They are most appropriate when excess weight is affecting health or creating significant future health risk, rather than simply because someone wants to be thinner.

For many adults with obesity — or overweight plus an important weight-related condition — medication can be considered alongside:

• good nutrition;
• physical activity;
• adequate protein;
• resistance exercise;
• sleep;
• ongoing medical care.

The newer GLP-1 and GIP/GLP-1 medicines can produce substantial weight loss and may improve several obesity-related diseases.

But treatment also involves:

• side effects;
• cost;
• pregnancy considerations;
• monitoring;
• long-term treatment decisions;
• the possibility of weight regain if treatment stops.

The best treatment is not the one that produces the fastest loss.

It is the one that produces meaningful, sustainable improvement in health.

Related Q Guides

• GLP-1 Weight-Loss Medicines: Benefits, Side Effects and Long-Term Use
• Snoring, Tired and Foggy? Could It Be Sleep Apnoea?
• Fatty Liver: What Your Results Mean and What You Can Do