Fact sheet

Weight and Obesity

Weight is a health issue, not a character test. Bodies defend their weight hard, so willpower alone rarely sticks. Losing just 5–10% brings real health benefits, and today’s treatments are far better than they were.

How it’s measured: a BMI of 25–29.9 is overweight and 30 or more is obesity. For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, risk starts lower (23 and 27.5). BMI can’t tell muscle from fat, so waist size helps: aim for under half your height.

Why it matters: obesity raises the risk of type 2 diabetes, heart disease, stroke, high blood pressure, fatty liver, osteoarthritis and some cancers, and can shorten life by 2–10 years. Day to day it can mean breathlessness, joint pain, snoring and low mood.

The good news: a 5–10% loss (5–10 kg for a 100 kg person) improves health and lowers the risk of many serious conditions. You don’t need to reach a “healthy BMI” to benefit.

The weight ladder

Pick a target your body can hold: 5–10% of your weight, at about 0.5–1 kg a week. Each step works better on top of the ones before it.

  1. Step 1 · Self-careEat a little less, consistentlyAny balanced, reduced-calorie pattern you can keep up: more vegetables, fruit and fibre, less sugar and fat, and fewer drinks with calories, alcohol included.
    Works
    A 5–10% loss improves health and lowers the risk of many serious conditions
    Cost
    Free, or cheaper than now
    How long
    Months; aim for 0.5–1 kg a week
    Watch for
    Crash diets backfire. Very low calorie diets need medical or dietitian supervision.

    The best diet is the one you’re still doing in six months.

  2. Step 2 · Self-careMove more, and lift thingsBuild up to 45–60 minutes of activity a day for weight loss (it can be split up), plus muscle strengthening on 2 days a week.
    Works
    Modest effect on weight alone; best combined with eating changes, and it improves health at any size
    Cost
    Free to low cost
    How long
    Ongoing
    Watch for
    Start where you are. Joint pain? Water-based or cycling exercise is kinder.

    You can’t outrun a bad diet, but you can out-walk a lot of health risk.

  3. Step 3 · Allied healthDietitian or structured programOne-to-one coaching, group programs, online support or CBT for eating habits.
    Works
    The standard next step in guidelines; results vary from person to person
    Cost
    Dietitian about $100–180 a visit; Medicare rebates for up to 5 allied health visits a year with a GP care plan
    How long
    Usually 3–12 months
    Watch for
    Commercial programs: check the full cost and what support continues after.

    A coach costs money. So does a cupboard full of failed gadgets.

  4. Step 4 · PrescriptionWeight-loss medicinesWeekly injections such as semaglutide or tirzepatide, which reduce appetite, or orlistat, which blocks some fat absorption. Used with diet and activity.
    Works
    Semaglutide: average 15% weight loss over 68 weeks vs 2.4% on placebo; about 86 in 100 lost at least 5%
    Cost
    Not on the PBS for weight loss; private scripts cost several hundred dollars a month
    How long
    Long term: weight tends to return when stopped (about 7% regained within a year in one trial)
    Watch for
    Nausea, vomiting, diarrhoea, constipation. Not in pregnancy, when planning it, or when breastfeeding. More in our weight-loss medicines guide.

    Not a shortcut, a tool. And tools only work while you use them.

  5. Step 5 · SpecialistWeight-loss (bariatric) surgeryFor a BMI of 40 or more, or 35 or more with a weight-related condition such as type 2 diabetes (lower cut-offs for some ethnic backgrounds).
    Works
    Usually the biggest and longest-lasting weight loss of any option
    Cost
    Public waiting lists are long; private costs vary widely, with large gaps even with insurance
    How long
    1–2 days in hospital, 3–4 weeks recovery, follow-up for at least 2 years
    Watch for
    Needs lifelong vitamins and check-ups.

    Major surgery for a major problem, not a cosmetic shortcut.

Costs are rough Australian prices in November 2026 and vary by pharmacy and provider. PBS co-payment: $25, or $7.70 with a concession card. Results are typical figures from trials, not promises.

Save your money

Popular, heavily marketed or often asked about, but the evidence is weak or says no.

What you can do

See your GP if

Pregnancy and contraception: weight-loss injections aren’t for pregnancy, when trying to conceive or when breastfeeding. Tirzepatide can make the contraceptive pill less reliable, so use a backup method such as condoms.

Common questions

How much weight do I need to lose to be healthier?

Losing 5 to 10% of your body weight improves health and lowers the risk of many serious conditions. For a 100 kg person that is 5 to 10 kg.

Do weight-loss injections work?

In the main semaglutide trial, people lost an average of 15% of their weight over 68 weeks, compared with 2.4% on placebo. Weight tends to come back when the medicine stops.

What is a healthy BMI?

For most adults 18.5 to 24.9. For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, health risks start at a lower BMI. Waist size under half your height is another useful guide.

Who can have weight-loss surgery?

Usually people with a BMI of 40 or more, or 35 or more with a weight-related condition such as type 2 diabetes or high blood pressure, with lower cut-offs for some ethnic backgrounds.

Helpful resources

Evidence and more information

Reviewed 1 November 2026. General education, not personal medical advice. Treatment depends on your situation, so talk to your GP, physio or pharmacist.

Related

maladywise.com/weight/