Australian weight-loss glossary

Adipose tissue

Body fat. Stores energy, secretes hormones (leptin, adiponectin) and provides thermal insulation. Subcutaneous adipose sits under the skin; visceral adipose surrounds abdominal organs and carries the higher cardiometabolic risk.

Basal metabolic rate(BMR)

Energy expenditure at complete rest in a fasting, thermoneutral state. Roughly 60 – 70% of total daily energy expenditure for a sedentary adult. Falls with weight loss – a major reason rapid loss is hard to maintain without structured behaviour change.

Brown adipose tissue(BAT)

Metabolically active adipose tissue that generates heat via uncoupled mitochondrial respiration. Present mainly in newborns; small depots remain in adults around the neck and clavicle. Active research area for obesity therapeutics; not yet a clinical pathway.

Ghrelin

Hormone secreted mainly by the stomach that increases appetite. Rises before meals, falls after eating. Sleeve gastrectomy removes the fundus where most ghrelin is produced, partly explaining its appetite-suppressing effect.

Leptin

Hormone secreted by adipose tissue that signals satiety and long-term energy stores to the hypothalamus. People with obesity generally have high circulating leptin but reduced sensitivity – the "leptin resistance" phenomenon.

Metabolic adaptation

Reduction in resting energy expenditure beyond what is predicted by loss of lean mass, observed after sustained calorie restriction. Important contributor to weight regain – often offset by pharmacotherapy or surgical intervention.

Resting metabolic rate(RMR)

Energy expenditure at rest, measured in less strict conditions than BMR. In practice the two terms are used interchangeably in weight-management settings.

Sarcopenia

Progressive loss of skeletal muscle mass and strength, accelerated by ageing, inactivity and rapid weight loss. Bariatric surgery and aggressive GLP-1 weight loss can both worsen sarcopenia without resistance training and adequate protein intake.

Set-point theory

Hypothesis that the body actively defends a particular weight range through metabolic and appetite mechanisms. Used to explain why sustained weight loss is biologically difficult – not a finalised model, but a useful framework when discussing why pharmacotherapy or surgery shifts the defended range.

Subcutaneous fat

Adipose tissue under the skin. Lower cardiometabolic risk than visceral fat. Distribution differs by sex – women typically carry more subcutaneous fat in hips and thighs; men typically more abdominal.

Thermic effect of food(TEF)

Energy used to digest, absorb and metabolise nutrients. About 10% of total intake on a mixed diet; higher for protein than carbohydrate or fat.

Total daily energy expenditure(TDEE)

Sum of BMR, the thermic effect of food, and physical activity. The reference quantity for a clinically calibrated calorie deficit.

Visceral fat

Adipose tissue stored around abdominal organs (liver, pancreas, intestines). Strongly associated with insulin resistance, Type 2 diabetes risk and cardiovascular disease, independent of total body weight.

Diabetes remission

HbA1c below the diabetes threshold (typically < 6.5%) for at least 3 months without glucose-lowering medication. Achievable for a meaningful proportion of patients with Type 2 diabetes under 10 years duration, particularly after sleeve gastrectomy or Roux-en-Y gastric bypass.

HbA1c

Glycated haemoglobin – a measure of average blood glucose over the prior 8 – 12 weeks. Australian diagnostic threshold for Type 2 diabetes is HbA1c ≥ 6.5% (48 mmol/mol). Used to monitor diabetes response to lifestyle, pharmacotherapy or bariatric surgery.

Source: racgp.org.au

Insulin resistance

Reduced cellular response to insulin, requiring higher insulin secretion to maintain glucose homeostasis. Precursor to Type 2 diabetes. Strongly correlated with visceral adiposity; improves with even modest weight loss.

Metabolic syndrome

Cluster of abdominal obesity, hypertension, dyslipidaemia and elevated fasting glucose that markedly raises cardiovascular and Type 2 diabetes risk. Common indication zone for bariatric or pharmacotherapy intervention.

Non-alcoholic fatty liver disease(NAFLD / MASLD)

Hepatic fat accumulation unrelated to alcohol intake. Strongly correlated with obesity and insulin resistance. Now commonly referred to as MASLD (metabolic dysfunction-associated steatotic liver disease). Improves with sustained weight loss.

Type 2 diabetes mellitus(T2DM)

Chronic metabolic disease characterised by insulin resistance and progressive pancreatic beta-cell dysfunction. Major driver of bariatric and GLP-1 treatment in Australia; the PBS subsidy for GLP-1 agents currently attaches to this indication.

Source: racgp.org.au

Body composition

Distribution of body mass across lean tissue, adipose tissue, bone and water. Measured by DEXA, bioimpedance or skinfold. More informative than weight alone for monitoring quality of weight loss.

Body mass index(BMI)

Weight (kg) divided by height (m) squared. WHO classifications: 18.5 – 24.9 normal, 25 – 29.9 overweight, 30 – 34.9 class I obesity, 35 – 39.9 class II, 40+ class III. Used as an entry-point screening tool; does not capture body composition or fat distribution.

Comorbidity

A clinical condition coexisting with the primary one. In weight-management context: Type 2 diabetes, hypertension, sleep apnoea, fatty liver disease, severe joint disease, polycystic ovary syndrome. The presence of comorbidities lowers the BMI threshold for surgical eligibility.

Dual-energy X-ray absorptiometry(DEXA)

Imaging modality that measures bone density and quantifies lean and fat mass. Used in bariatric clinics to monitor preservation of lean mass through weight loss.

Indirect calorimetry

Measurement of resting energy expenditure via gas exchange. Used in specialist clinics to calibrate calorie targets when standard BMR equations are unreliable (e.g. after bariatric surgery).

Waist circumference

Measured at the midpoint between the lowest rib and the iliac crest. Australian increased-risk thresholds: > 94 cm men, > 80 cm women. Cardiometabolic-risk thresholds: > 102 cm men, > 88 cm women.

Source: health.gov.au

Waist-to-hip ratio(WHR)

Ratio of waist to hip circumference. Captures fat distribution. WHO increased-risk thresholds: > 0.90 men, > 0.85 women.

Adjustable gastric band(Lap-Band)

Silicone band placed around the upper stomach with an adjustable port. Largely superseded by sleeve and bypass in Australia due to long-term complication and revision rates; still selected by some patients for its reversibility.

ANZMOSS

Australian and New Zealand Metabolic and Obesity Surgery Society. Peak professional body for bariatric and metabolic surgery in Australia and New Zealand. Publishes position statements that guide indication, training and accreditation expectations.

Source: anzmoss.com.au

Bariatric surgery

Surgical procedures performed primarily for weight management and the treatment of weight-related disease. Australian indication: BMI ≥ 35 with comorbidities or BMI ≥ 40 regardless. Performed by FRACS-credentialled surgeons in accredited centres.

Source: anzmoss.com.au

Bariatric Surgery Registry(BSR)

National clinical-quality registry operated by Monash University capturing outcomes from participating bariatric centres across Australia. Annual reports describe procedure mix, weight-loss trajectories and complication rates.

Biliopancreatic diversion with duodenal switch(BPD-DS)

Sleeve gastrectomy combined with diversion of bile and pancreatic enzymes to the distal small bowel. Most malabsorptive of the common bariatric operations; reserved for selected high-BMI patients due to nutritional risk.

Dumping syndrome

Cluster of vasomotor and gastrointestinal symptoms after rapid emptying of high-osmolarity food (typically simple sugars) from the stomach into the small intestine. Common early after gastric bypass; usually manageable with dietary change.

Endoscopic sleeve gastroplasty(ESG)

Non-surgical reduction of stomach volume via endoscopic suturing. Offered at select Australian centres for patients between medical management and surgical eligibility. Lower weight loss than surgical sleeve; reversible in principle.

Gastric plication

Operation in which the stomach is folded inward and sutured to reduce volume, without resection. Not in the mainstream of Australian practice; mostly historical.

Internal hernia

Bowel herniation through mesenteric defects created at gastric bypass. Rare but serious post-RYGB complication; presents as intermittent abdominal pain; surgical emergency if obstructed.

Intragastric balloon

Temporary endoscopically placed balloon (typically 6 – 12 months) that occupies gastric volume. Modest weight-loss tool; primarily a bridge to surgery or to engage with lifestyle change.

Metabolic surgery

Synonym for bariatric surgery, emphasising the metabolic effects (diabetes remission, blood-pressure improvement) rather than weight loss alone. Term preferred by ANZMOSS and increasingly by the international literature.

Source: anzmoss.com.au

Mini gastric bypass(MGB / OAGB)

One-anastomosis gastric bypass. Single loop reconstruction; technically simpler than Roux-en-Y. Effective weight-loss outcomes; bile-reflux risk debated. Performed by a minority of Australian centres.

Revisional bariatric surgery

Operation performed to address complications or weight regain after a previous bariatric procedure. Common conversions: sleeve → bypass, band removal → sleeve, sleeve → SADI-S.

Roux-en-Y gastric bypass(RYGB)

Creation of a small gastric pouch anastomosed to the jejunum (Roux limb), bypassing the remainder of the stomach and proximal small intestine. Strongest reflux protection of the common bariatric procedures and superior diabetes-remission outcomes.

Source: anzmoss.com.au

Single-anastomosis duodenal switch(SADI-S / SIPS)

Single-anastomosis variant of duodenal switch. Strong weight-loss and diabetes-remission outcomes. Offered by a smaller number of Australian centres.

Source: anzmoss.com.au

Sleeve gastrectomy

Removal of approximately 75 – 80% of the stomach along the greater curvature, leaving a narrow tube. Australia’s most-performed primary bariatric operation (~60 – 70% of cases). Average loss 25 – 30% body weight at 12 – 24 months.

Source: anzmoss.com.au

Authority Required

PBS authority status. Prescriber must obtain approval from Services Australia (or use streamlined authority code) to write a PBS-subsidised script. GLP-1 agents for Type 2 diabetes are typically Authority Required (Streamlined).

Source: pbs.gov.au

Compounded medicine

Medicine prepared by a pharmacist for an individual patient. TGA tightened the regulation of compounded GLP-1 agents from 1 October 2024 – compounded versions should not be used where the registered product is available except under narrow individual-patient exemptions.

Source: tga.gov.au

Dual incretin agonist

Medicine that activates both the GIP and GLP-1 receptors. Tirzepatide is a dual incretin agonist available in Australia.

Dulaglutide

A weekly-injection GLP-1 receptor agonist active ingredient used for Type 2 diabetes.

Source: tga.gov.au

GIP

Glucose-dependent insulinotropic polypeptide. Incretin hormone with effects on insulin secretion, lipid metabolism and appetite. Targeted alongside GLP-1 by tirzepatide.

GLP-1

Glucagon-like peptide-1. Incretin hormone released by the gut after a meal that increases insulin secretion, decreases glucagon, slows gastric emptying and increases satiety. GLP-1 receptor agonists are designed analogues of this hormone.

GLP-1 receptor agonist

Class of medicines that bind the GLP-1 receptor, used for Type 2 diabetes and, for selected agents, chronic weight management. Active ingredients in this class include semaglutide, liraglutide and dulaglutide.

Liraglutide

A daily-injection GLP-1 receptor agonist active ingredient, used (depending on the product) for chronic weight management or Type 2 diabetes.

Source: tga.gov.au

Naltrexone–bupropion

An oral combination medicine (an opioid receptor antagonist with an aminoketone antidepressant) used for chronic weight management.

Source: tga.gov.au

Orlistat

A pancreatic lipase inhibitor available on prescription and, at a lower dose, over the counter. Modest weight-loss effect; significant gastrointestinal side effects limit adherence.

PBAC

Pharmaceutical Benefits Advisory Committee. Independent statutory body that recommends medicines for PBS listing on the basis of clinical effectiveness, safety and cost-effectiveness. In November 2025 PBAC recommended a weight-management medicine for PBS listing for the narrow cohort of obesity with established cardiovascular disease.

Source: pbs.gov.au

Pharmaceutical Benefits Scheme(PBS)

Australian federal subsidy scheme for prescription medicines. GLP-1 receptor agonist PBS subsidies currently attach to the Type 2 diabetes indication, not weight management.

Source: pbs.gov.au

Phentermine

A sympathomimetic appetite suppressant. Short-term use only under prescriber supervision; not first-line in current Australian guidance.

Schedule 4

Prescription-only medicine class under the Poisons Standard. All GLP-1 receptor agonists in Australia are Schedule 4 – they cannot lawfully be supplied without a current Australian prescription from an AHPRA-registered prescriber.

Source: tga.gov.au

Semaglutide

A GLP-1 receptor agonist active ingredient. Depending on the product and dose, it is registered in Australia for Type 2 diabetes or chronic weight management.

Source: tga.gov.au

Tirzepatide

A dual GIP/GLP-1 receptor agonist active ingredient, TGA-approved in Australia for both Type 2 diabetes and chronic weight management.

Source: tga.gov.au

Accredited Practising Dietitian(APD)

Credential awarded by Dietitians Australia. The recognised standard for dietetic practice in Australia. Bariatric pre-op and post-op dietetic care should be APD-led.

Behavioural weight management

Structured program combining dietary change, physical activity, behaviour-change techniques and ongoing review. First-line treatment for overweight and class I obesity in Australian guidance; foundational alongside pharmacotherapy and surgery.

Binge eating disorder(BED)

Recurrent episodes of eating a large amount of food in a discrete period with loss of control. Screened for as part of the bariatric pre-op pathway and any structured pharmacotherapy program. Treatment is psychological, not surgical.

Plateau

Period during weight management where loss stalls despite continued adherence. Universal experience; addressed by re-baselining intake against current TDEE, behaviour-change review or pharmacotherapy adjustment.

Protein leverage

Hypothesis that protein intake drives total energy intake – when protein is diluted in the diet, total intake rises to compensate. Practical implication: protein-prioritised eating supports weight management.

Resistance training

Strength training using bodyweight, free weights, machines or bands. Preserves lean mass during weight loss; non-negotiable companion to GLP-1 therapy and bariatric surgery for protecting muscle and BMR.

Very low-calorie diet(VLCD)

Structured meal-replacement program providing typically 600 – 800 kcal/day. Used clinically for short periods, often as a pre-bariatric "liver shrinking" diet for 2 weeks, or under a structured medical weight-loss program. Optifast and Formulite are common Australian brands.

AHPRA

Australian Health Practitioner Regulation Agency. Administers the National Registration and Accreditation Scheme for 16 regulated health professions. Practitioner registration can be verified at the AHPRA public register.

Source: ahpra.gov.au

Australian Bureau of Statistics(ABS)

National statistical agency. Publishes the National Health Survey which reports adult overweight and obesity prevalence in Australia.

Source: abs.gov.au

Dietitians Australia

National professional body for dietitians. Awards the Accredited Practising Dietitian (APD) credential. Maintains a public find-a-dietitian service.

Source: dietitiansaustralia.org.au

RACGP

Royal Australian College of General Practitioners. Sets standards for general practice in Australia and publishes guidance on obesity management.

Source: racgp.org.au

RACS

Royal Australasian College of Surgeons. Surgical training, certification and continuing professional development body for Australia and New Zealand. Bariatric surgeons in Australia are FRACS (General Surgery), typically with further bariatric fellowship training.

Source: surgeons.org

TGA Schedule 4 advertising restriction

Section 42DL of the Therapeutic Goods Act 1989 prohibits direct-to-consumer advertising of Schedule 4 (prescription-only) medicines. Consumer health information is permitted only if it does not promote use, makes no therapeutic claim and refers readers to a qualified prescriber.

Source: tga.gov.au

Therapeutic Goods Administration(TGA)

Australia’s national medicines and medical-devices regulator within the Department of Health. Approves medicines for sale, monitors safety, maintains the Australian Register of Therapeutic Goods, the Medicine Shortage Reports Database and the Therapeutic Goods Advertising Code.

Source: tga.gov.au