Adult obesity: assessment and management
Non-pregnant adults (18 years or older). Obesity: BMI 30 kg/m² or more (27.5 or more in Asian, Aboriginal and Torres Strait Islander people), or a high waist circumference.
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Family MedicineManagement
Adult Obesity Evaluation & Management (ADS 2026)
Adult Obesity Evaluation & Management (ADS 2026): Adult obesity: assessment and management → Pregnancy, age under 18 or eating disorder: use other care ...
Pathway Overview
20 steps
Algorithm Steps
20 total
01Start 02Warning Pregnancy, age under 18 or eating disorder: use other care
This pathway is for non-pregnant adults.
- Pregnant, planning pregnancy or breastfeeding: do not start weight-loss medicines or a VLED
- Under 18 years: refer to a paediatric or adolescent obesity service
- Current or past anorexia or bulimia: get specialist advice first; naltrexone-bupropion and phentermine are contraindicated
03Action Comprehensive evaluation
Measure BMI and waist circumference. Look for causes, complications and barriers.
- High waist: more than 88 cm (women) or 102 cm (men); Asian, Aboriginal and Torres Strait Islander people: more than 80 cm (women) or 90 cm (men)
- Review drugs that cause weight gain (for example antipsychotics, insulin, sulfonylureas, corticosteroids)
- Test for secondary causes when suspected: hypothyroidism, Cushing's syndrome
- Screen for depression, binge eating, food insecurity and past weight-loss attempts
- Look for complications: T2DM or prediabetes, hypertension, dyslipidaemia, MAFLD, OSA, PCOS, osteoarthritis, CVD
04Action Treat obesity-related complications
Treat each complication in parallel with weight management. Repeat this assessment at regular intervals.
- OSA: screen (for example STOP-Bang); sleep study if positive
- MAFLD: assess fibrosis risk (for example FIB-4)
- T2DM: prefer glucose-lowering drugs that do not cause weight gain
- Treat hypertension, lipids and mental health to usual targets
05Action Classify obesity and set a weight-loss target
Use BMI, waist and complications (ADS 2026). Agree a personal target with the patient.
- BMI 30-40 (Asian, Aboriginal and Torres Strait Islander: 27.5-37.5) without complications: target 10-15% loss; manage in primary care
- BMI 30-40 with complications, or above 40 without: target 10-15%; use intensive options (VLED, medicine or surgery); consider shared care with a specialist service
- BMI above 40 (Asian, Aboriginal and Torres Strait Islander: above 37.5) with complications: target more than 15%; refer to specialist care; recommend surgery assessment
- Surgery can be discussed at any step if criteria are met; BMI 35 or more does not need a failed drug trial first
- Age over 65: aim to keep physical function; use a more moderate weight-loss target
06Action Supervised lifestyle intervention (all patients)
Foundation for every treatment option. Continue it with medicines and after surgery.
- Reduced energy diet: deficit of 2000-4000 kJ/day (480-960 kcal/day)
- Or low energy diet: 4200-5000 kJ/day (1000-1200 kcal/day), for example 1-2 meal replacements a day
- Activity: 150-300 min/week moderate (or 75-150 min vigorous), plus muscle strengthening on 2 days/week
- Refer to a dietitian, exercise physiologist or psychologist as needed
07Action Not enough weight loss: consider a VLED
Very low energy diet (less than 3300 kJ/day, meal replacements), with or without a medicine. Review at least monthly.
- On insulin or a sulfonylurea: reduce the dose by 50% when the VLED starts; monitor glucose
- On an SGLT2 inhibitor: monitor ketones or consider stopping it (risk of euglycaemic DKA)
- Do not use in pregnancy, lactation, recent MI, stroke or unstable angina, severe psychiatric illness, alcohol or drug dependence, porphyria
- Caution: age over 65, eGFR below 60 mL/min/1.73 m²; warfarin: check INR 1 week after starting
- Add 1 teaspoon of olive oil a day to lower gallstone risk
08Decision Eligible for a weight-loss medicine?
Lifestyle not enough (or complications present), and BMI 30 kg/m² or more, or 27 or more with a weight-related condition.
- Weight-related conditions: T2DM or prediabetes, hypertension, dyslipidaemia, OSA, CVD
- If Yes
09Warning Before any weight-loss medicine: check contraindications
Eligible for a medicine: check these first.
- Opioid use (including methadone or buprenorphine), seizures or bipolar disorder: do not use naltrexone-bupropion
- Heart or cerebrovascular disease, arrhythmia, pulmonary hypertension, valve disease, moderate-severe hypertension, hyperthyroidism, glaucoma, depression or other psychiatric illness, drug or alcohol misuse: do not use phentermine
- MAOI in the past 14 days: do not use naltrexone-bupropion or phentermine
10Action Eligible: choose a TGA-registered medicine
ADS 2026: usually semaglutide 2.4 mg (Wegovy) or tirzepatide (Mounjaro). Established CVD: semaglutide 2.4 mg reduced major CV events by 20% (SELECT). Moderate-severe OSA: tirzepatide is TGA-registered. Out-of-pocket cost can be high.
- Semaglutide 2.4 mg weekly (Wegovy): mean loss about 15-17% (STEP 1)
- Tirzepatide 5, 10 or 15 mg weekly (Mounjaro): mean loss 15%, 19.5% and 21% (SURMOUNT-1)
- Liraglutide 3 mg daily (Saxenda): mean loss about 8% (SCALE)
- Naltrexone-bupropion (Contrave): mean loss about 6% (COR-I)
- Phentermine (Duromine, Metermine): 5-10% loss at 12 weeks; short-term use only
- Orlistat (Xenical): about 3-4 kg more loss than placebo (XENDOS); limited availability in Australia (veterans' scheme)
- Phentermine-topiramate is not TGA-registered for weight loss; off-label, specialist use only
11Action If semaglutide or tirzepatide: dosing and safety
Weekly subcutaneous injection. Increase the dose every 4 weeks or slower to limit nausea and vomiting.
- Semaglutide (Wegovy): 0.25 mg weekly, then 0.5, 1 and 1.7 mg (4 weeks each), then 2.4 mg maintenance
- Tirzepatide (Mounjaro): 2.5 mg weekly for 4 weeks, then 5 mg; increase by 2.5 mg after 4 weeks or more; maintenance 5, 10 or 15 mg; maximum 15 mg
- Already on another GLP-1 RA (for example Ozempic, Trulicity): do not combine; switch. Stop a DPP-4 inhibitor
- Pregnancy: use contraception; stop semaglutide at least 2 months and tirzepatide at least 1 month before a planned pregnancy
- Tirzepatide and oral contraceptive: switch to a non-oral method or add a barrier method for 4 weeks after starting and after each dose increase
- On insulin or a sulfonylurea: risk of hypoglycaemia; consider a lower dose of these drugs
- Before anaesthesia or sedation: do not stop routinely; clear fluids for 24 hours, then 6-hour fast; tell the anaesthetist
- Stop if pancreatitis is suspected; caution after past pancreatitis; risk of gallbladder disease
- Vomiting or diarrhoea: risk of dehydration and acute kidney injury
- Diabetic retinopathy: monitor closely. Sudden vision loss: urgent eye review; stop semaglutide if NAION is confirmed
- Monitor mood and for suicidal thoughts. Personal or family history of MTC or MEN2: do not use (US label)
- Wegovy 7.2 mg weekly (3 injections of 2.4 mg): option if BMI 30 or more at start, after at least 4 weeks on 2.4 mg
12Action If another medicine: dosing and safety
Naltrexone-bupropion, phentermine, liraglutide or orlistat.
- Naltrexone-bupropion (Contrave 8/90): 1 tablet in the morning; add 1 tablet each week to 2 tablets twice daily from week 4
- Naltrexone-bupropion: maximum 1 tablet twice daily if moderate or severe renal impairment, or with clopidogrel or ticlopidine; not recommended in hepatic impairment; do not combine with other bupropion (Zyban)
- Naltrexone-bupropion: also not for uncontrolled hypertension, bulimia or anorexia, CNS tumour, alcohol or benzodiazepine withdrawal, pregnancy, severe liver disease or end-stage kidney failure
- Naltrexone-bupropion: check BP and pulse before and during; monitor for suicidal thoughts; stop at least 3 days before planned opioid use
- Phentermine: 15-40 mg once in the morning (start 15-30 mg); review by 3 months; not for the elderly; do not use with SSRIs or other antidepressants
- Liraglutide 3 mg (Saxenda): 0.6 mg daily; increase by 0.6 mg each week to 3 mg daily; same cautions as other GLP-1 RAs
- Orlistat 120 mg three times a day: oily stools; fat-soluble vitamin loss; do not use in chronic malabsorption, cholestasis or pregnancy
13Decision At least 5% weight loss at 3 months?
Measure at 3 months on the maintenance or highest tolerated dose (naltrexone-bupropion: at 16 weeks).
- If Yes
14Action Responding (5% or more): continue long term
Obesity is a chronic disease. Most people regain weight when a medicine stops.
- Continue the medicine with the lifestyle programme
- Phentermine is for short-term use only
- Still BMI 35 or more, or T2DM with BMI 30 or more: discuss bariatric surgery
- Monitor side effects, BP, glucose and lipids; reduce glucose-lowering drugs as needed
- Include resistance exercise to protect muscle mass
15Outcome Long-term chronic disease care
Review weight, complications and treatment at regular intervals.
If No16Action Not responding (less than 5%): stop and change plan
Check adherence, dose and side effects first.
- Stop a medicine that has not given 5% loss at 3 months
- Consider one other medicine, or a VLED with a medicine
- Refer to a specialist obesity service if still not responding or complications are present
17Decision Meets criteria for metabolic bariatric surgery?
ASMBS/IFSO 2022: BMI 35 or more (with or without complications); BMI 30 or more with T2DM; BMI 30-34.9 without lasting benefit from non-surgical care. Asian people: from BMI 27.5.
- NHMRC 2013 (cited by ADS 2026): BMI above 40; 35-39.9 with complications; 30-34.9 with poorly controlled T2DM and high CV risk
- A failed drug trial is not required before surgery at BMI 35 or more
- Public service criteria and waiting times vary by state
- If Yes
18Action Eligible: refer for bariatric surgery assessment
Most effective and durable weight-loss treatment. Needs a multidisciplinary team and lifelong follow-up.
- Team: surgeon, physician, dietitian and psychologist; optimise health before surgery
- The surgical team chooses the procedure (for example sleeve gastrectomy or gastric bypass)
- Lifelong vitamin and mineral supplements and blood tests
- On a GLP-1 RA or tirzepatide: follow ADS/ANZCA 2025 advice before anaesthesia
- Path rejoins step 15Shared downstream outcome
If No19Action Not eligible or declines surgery: intensify medical care
Continue lifestyle care. Treat complications.
- Consider a VLED with a medicine (ADS 2026)
- Refer to a specialist obesity service if BMI above 40 or complications are present
- Reassess surgery if BMI or complications change
- Path rejoins step 15Shared downstream outcome
If No20Action Not eligible for a medicine: continue lifestyle care
Keep the lifestyle programme and treat complications.
- Reassess weight, waist and complications at regular intervals
- Reconsider a medicine if BMI or complications change
- Path rejoins step 15Shared downstream outcome
Guideline Source
Australian Obesity Management Algorithm (Australian Diabetes Society), January 2026 update
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- Adults only: not for children, adolescents, pregnancy or breastfeeding
- Medicines, brands and doses are for Australia (TGA); availability, indications and brands differ in other countries
- Weight-loss medicines have a high out-of-pocket cost; access to public bariatric surgery varies by state
- Does not give full VLED prescribing detail or long-term post-bariatric care
- Weight thresholds for Asian populations are from ADS 2026 and ASMBS/IFSO 2022; other ethnic groups may also need lower thresholds
Contraindicated Populations
pregnancybreastfeedingpediatric
Applicable Regions
USAUUKEU
AU: Australian Obesity Management Algorithm (ADS, January 2026) and TGA product information.
EU: Phentermine is not authorised; naltrexone-bupropion is Mysimba.
UK: Phentermine is not licensed; naltrexone-bupropion is Mysimba. Follow NICE obesity guidance.
US: Tirzepatide for weight management is Zepbound; phentermine-topiramate ER (Qsymia) is FDA-approved. See Endocrine Society 2015 and AGA 2022 obesity drug guidelines.
Version 2Next review: 2027-09-30
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Frequently Asked Questions
What is the Adult Obesity Evaluation & Management (ADS 2026)?
The Adult Obesity Evaluation & Management (ADS 2026) is a management clinical algorithm for Family Medicine. It provides a structured decision tree to guide clinical decision-making, based on Australian Obesity Management Algorithm (Australian Diabetes Society), January 2026 update.
What guideline is the Adult Obesity Evaluation & Management (ADS 2026) based on?
This algorithm is based on Australian Obesity Management Algorithm (Australian Diabetes Society), January 2026 update.
What are the limitations of the Adult Obesity Evaluation & Management (ADS 2026)?
Known limitations include: Adults only: not for children, adolescents, pregnancy or breastfeeding; Medicines, brands and doses are for Australia (TGA); availability, indications and brands differ in other countries; Weight-loss medicines have a high out-of-pocket cost; access to public bariatric surgery varies by state; Does not give full VLED prescribing detail or long-term post-bariatric care; Weight thresholds for Asian populations are from ADS 2026 and ASMBS/IFSO 2022; other ethnic groups may also need lower thresholds. Individual patient factors may require deviation from these recommendations.
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