GC064 I Am Overweight, Doctor
A clinical consultation addressing a patient's concern about excess body weight, involving assessment of BMI, identification of contributing factors, and discussion of lifestyle modifications and management strategies to achieve a healthier weight.
I Am Overweight, Doctor — Obesity & Hyperlipidaemia
This lecture is a core General Clerkship session covering obesity from definition and measurement all the way through aetiology, complications, and management (lifestyle, pharmacology, surgery). It is highly examinable because obesity intersects with virtually every system: cardiovascular, endocrine, respiratory, orthopaedic, surgical, psychiatric, and obstetric. The examiners love asking about:
- Hong Kong/Asian action points vs international WHO BMI categories (a classic MCQ discriminator).
- Waist circumference cut-offs (ethnic-specific).
- Secondary causes of obesity and medications causing weight gain (commonly tested lists).
- Pharmacotherapy — mechanism, side effects, and which drugs have been withdrawn.
- Bariatric surgery indications and types (SAQ/minicase territory).
- Complications of obesity (systems-based list).
The lecture also touches on leptin physiology and the concept of adipose tissue as an endocrine organ — tested in SAQs that ask "why is sustained weight loss difficult?"
1. Measurements to Quantify Obesity
"BMI does not provide any indication of the distribution of fat." [1]
BMI = weight (kg) / height (m)² [1]
- A simple, widely used screening tool.
- Critical limitation: BMI tells you total mass relative to height but says nothing about where fat is distributed. A muscular rugby player and a sedentary person can share the same BMI with very different health risks.
High Yield — Asian BMI Cut-Offs
WHO Expert Consultation 2004: cardiometabolic risk in Asian populations becomes substantial at lower BMI values, so country-specific action points may be appropriate. [1]
Many Asian populations develop type 2 diabetes and cardiovascular risk at lower BMI values than many European-origin populations; BMI also incompletely captures visceral and ectopic fat. This is the clinical rationale for lower Hong Kong action thresholds.
| Classification | International WHO categories | Hong Kong adult categories | Risk framing |
|---|---|---|---|
| Underweight | < 18.5 | < 18.5 | Other nutritional risks increase |
| Normal / acceptable | 18.5–24.9 | 18.5–22.9 | Baseline category, not “no risk” |
| Overweight | 25–29.9 | 23.0–24.9 | Risk is already increased at a lower BMI in many Asian populations |
| Obesity | ≥ 30 | ≥ 25.0 | Hong Kong further records BMI 25.0–29.9 and ≥30 as increasing severity |
How to reconcile the two Asian slides
The 2004 WHO consultation did not create one universal Asian classification. One slide shows WHO risk-action points at 23.0 and 27.5 kg/m²; the next shows the Hong Kong/IOTF-style clinical categories used in the lecture (overweight 23.0–24.9, obesity ≥25.0). State which framework you are using rather than mixing them. [1][13]
"Increasingly used as a measure of central obesity. Ethnic differences recognised (IDF 2005)." [1]
| Population | Men | Women |
|---|---|---|
| Europids | ≥ 94 cm | ≥ 80 cm |
| Chinese | ≥ 90 cm | ≥ 80 cm |
Why WC complements BMI: Adipose tissue in a truncal distribution (around and in the abdomen) has a particularly strong relationship with the adverse metabolic and vascular effects of obesity [1]. Visceral fat is metabolically active — it secretes pro-inflammatory cytokines, contributes to insulin resistance, and drives atherogenesis in a way that subcutaneous gluteo-femoral fat does not.
WHO: WHR ≥ 0.9 in men, WHR ≥ 0.85 in women [1]
WHR is an older measure that captures the "apple vs pear" body shape concept. It supplements WC but in modern practice WC alone is more commonly used clinically.
- Skin-fold thickness — calipers measure subcutaneous fat at standardised sites. Research tool, not practical in clinic.
- Estimates of total body fat — DEXA and laboratory methods can estimate body composition; bioelectrical impedance is convenient but hydration-dependent. These are not required for routine diagnosis or management. [1]
"Among persons aged 15–84 by BMI: 30% obese, 20% overweight." [1]
| Parameter | Male | Female |
|---|---|---|
| Obese (BMI ≥ 25 Asian) | 36% | 24% |
| Overweight (BMI 23–24.9 Asian) | 21% | 19% |
| Central obesity by WC | 28% | 37% |
Key epidemiological observations from the lecture:
- Proportion classified as overweight/obese decreased with increasing household income — inverse socioeconomic gradient, consistent with international data. Lower-income groups have poorer access to healthy food and exercise facilities. [1]
- Prevalence of central obesity generally increases with age — as lean mass declines, hormonal changes (especially post-menopause) favour visceral fat deposition. [1]
Update — these percentages are historical
The table above is the 2014/15 survey reproduced in the slide, not a current prevalence estimate. Hong Kong's Population Health Survey 2020–22 found, among people aged 15–84 who underwent health examination, 32.6% with obesity (BMI ≥25) and another 22.0% with overweight (BMI 23.0–24.9); central obesity by waist circumference was 37.8%. [13]
This is a classic exam list. The lecture organises it by system, which is exactly how you should reproduce it in an SAQ.
| System | Conditions |
|---|---|
| Cardiovascular | Hypertension, Coronary heart disease, Stroke |
| Metabolic | Type 2 DM, Dyslipidaemia, Insulin resistance, PCOS |
| Gastrointestinal | Hiatus hernia, Gallstones, Colorectal cancer, Non-alcoholic hepatic steatosis (MASLD) |
| Respiratory | Breathlessness, Obstructive sleep apnoea, Hypoventilation (Obesity hypoventilation syndrome / Pickwickian) |
| Neurological | Nerve entrapment, Sciatica |
| Breast | Breast cancer, Gynaecomastia |
| Genitourinary | Stress incontinence, Reduced fertility (PCOS), Pregnancy complications |
| Orthopaedic | Osteoarthritis of weight-bearing joints |
| Psychological | Poor self-esteem, Depression |
Why these complications occur — from first principles:
- CV: Excess adiposity → ↑ circulating volume → ↑ cardiac output → ↑ BP. Also accelerated atherosclerosis from dyslipidaemia + chronic inflammation.
- T2DM / Insulin resistance: Visceral fat → ↑ free fatty acids → lipotoxicity to pancreatic β-cells + ↓ insulin sensitivity in muscle/liver.
- OSA: Fat deposition around pharynx → airway collapse during sleep → intermittent hypoxia → daytime somnolence, pulmonary hypertension, arrhythmias. [4]
- Gallstones: Obesity → ↑ cholesterol secretion into bile → supersaturation → cholesterol stones. The "4 Fs" mnemonic: Fat, Female, Forty, Fertile. [5]
- MASLD: Insulin resistance → ↑ hepatic de novo lipogenesis + impaired VLDL export → hepatic steatosis → potential progression to steatohepatitis → cirrhosis. [6]
- OA: Mechanical overload on weight-bearing joints + adipokine-mediated low-grade inflammation.
- Breast cancer: Adipose tissue aromatises androgens to oestrogens (especially post-menopause) → oestrogen-driven tumour growth.
"Risk of CHD doubled if BMI > 25 and quadrupled if BMI ≥ 29." [1]
This is an older cohort-level estimate reproduced from the slide, not an individual risk calculator. Cardiovascular risk is continuous and also depends on age, smoking, blood pressure, glycaemia, lipids, fat distribution and established disease.
High Yield
"As weight reduction can alleviate obesity-associated co-morbidities, the goal of obesity treatment should be in the reduction of co-morbidity rather than for cosmetic reasons." [1]
This is a commonly tested concept — the examiner wants you to frame management in terms of health benefit, not appearance.
4. Aetiology of Obesity
"Mismatch between energy intake and energy expenditure." [1]
This is thermodynamics: if calories in > calories out, excess energy is stored as fat. But it is oversimplistic to tell patients to "just eat less" — the regulation of energy balance is a tightly controlled neuro-hormonal system.
- Only very few cases of obesity solely due to single-gene defect (e.g. leptin deficiency, MC4R mutations — extremely rare in humans). [1]
- Genetic influences are generally polygenic. [1]
- The slide quotes heritability of about 33% from older adoption/segregation studies. [1]
- Do not interpret heritability as “one-third of an individual's obesity is genetic.” It is a population- and environment-specific estimate of variation, and it does not partition a person's weight into genetic versus lifestyle percentages.
"Obesity is associated with food intake and content of fat in diet; sedentary lifestyle; inverse relationship between socio-economic status and the prevalence of obesity." [1]
- Calorie-dense, high-fat foods are cheap and accessible.
- Modern lifestyles promote sitting (desk jobs, screen time, driving).
- The socioeconomic gradient is context-dependent and reflects food environment, working conditions, housing, stress, access to care and opportunities for activity; it should not be reduced to individual “health literacy.”
These are endocrine or hypothalamic conditions associated with weight gain or altered body composition. Test selectively when the history/examination suggests them; routine broad endocrine screening is not required for every person with obesity. PCOS and obesity have a bidirectional association rather than PCOS being a simple one-way cause.
Conditions associated with obesity: [1]
- Hypothyroidism
- Cushing's syndrome
- Hypothalamic tumours (e.g. craniopharyngioma → disrupts satiety centre)
- Growth hormone deficiency
- Hypogonadism in males — associated with increase in abdominal and visceral fat
- Polycystic ovary syndrome
Exam Approach — Cushing's vs Simple Obesity
A 2022 MCQ (Q9) tests this distinction: woman with oligomenorrhoea, weight gain, moon facies, proximal weakness, thin skin, purplish striae, and BMI 27 → answer is Cushing syndrome, not simple obesity or PCOS. The discriminators are the catabolic signs—easy bruising/thin skin, proximal myopathy and wide violaceous striae—which are not features of uncomplicated obesity. [3]
Common medications causing weight gain: [1]
| Drug Class | Examples |
|---|---|
| Antidepressants | MAOIs, TCAs (nortriptyline, amitriptyline, doxepin), paroxetine, citalopram, escitalopram, imipramine, mirtazapine |
| Antipsychotics | Thioridazine, olanzapine, risperidone, clozapine, quetiapine |
| Diabetes medications | Insulin, sulfonylureas, thiazolidinediones (TZDs), meglitinides |
| Glucocorticoids | Prednisone |
| Anticonvulsants | Valproate, carbamazepine |
Why these cause weight gain:
- Olanzapine/clozapine: potent H1 antihistamine + 5-HT2C blockade → ↑ appetite centrally. Among antipsychotics, olanzapine and clozapine cause the most weight gain.
- Insulin/SU/TZDs: promote anabolism; insulin promotes lipogenesis and inhibits lipolysis; TZDs cause adipocyte differentiation (paradoxically improving insulin sensitivity by expanding subcutaneous fat capacity but causing weight gain).
- Steroids: cortisol → ↑ gluconeogenesis, ↑ appetite, redistribution of fat to truncal/visceral compartments.
- Valproate: mechanism unclear but likely involves ↑ appetite + effects on fatty acid metabolism.
- Mirtazapine: H1 + 5-HT2C blockade → significant appetite stimulation.
Important Clinical Pearl
When a patient presents with weight gain, review the medication list, dose and timing. Consider weight-neutral or weight-lowering alternatives where clinically appropriate, but do not stop or switch antipsychotic or glucose-lowering treatment without the prescribing team: psychiatric stability, glycaemia, contraindications, affordability and patient preference all matter.
5. Regulation of Energy Balance — Leptin & Adipose Tissue Physiology
"Hypothalamus — a centre for regulation of energy balance. Integrates neural, hormonal and nutrient messages from the body and sends signals to higher centres leading to feeling of hunger or satiety. Controls energy expenditure via autonomic nervous system and pituitary hormones." [1]
The hypothalamus contains two key nuclei:
- Arcuate nucleus: contains POMC/CART neurons (anorexigenic — suppress appetite) and NPY/AgRP neurons (orexigenic — stimulate appetite).
- These receive input from leptin, ghrelin, insulin, GLP-1, PYY, and nutrient signals (glucose, fatty acids, amino acids).
"Peptide hormone synthesised by adipocytes. Acts in the hypothalamus to suppress food intake and increase energy expenditure." [1]
Key lecture points on leptin:
- Mutation in leptin gene → ob/ob mice; Mutation in leptin receptor gene → db/db mice, fa/fa rat. [1]
- Mutations in leptin or leptin receptor as a cause of obesity are extremely rare in humans. [1]
- Leptin levels rise in parallel with fat mass. [1]
- Leptin concentration is increased in obese subjects. [1]
- Human obesity is NOT a state of leptin deficiency or of extreme leptin insensitivity → ? Partial resistance. [1]
Why this matters: This explains why metreleptin is not a general treatment for common obesity (unlike replacement in rare congenital leptin deficiency or selected lipodystrophy). Most people with obesity have leptin concentrations appropriate to increased fat mass, with attenuated biological response often described as leptin resistance. The system strongly defends against weight loss.
"Adipose tissue is NOT an inert tissue. It is a major endocrine and secretory organ. Releases a wide range of protein factors and signals termed adipokines (e.g. adiponectin), in addition to fatty acids and other lipid moieties." [1]
Adipokines include:
- Leptin — satiety signal (see above)
- Adiponectin — insulin-sensitising, anti-inflammatory, anti-atherogenic. Levels are decreased in obesity (paradoxically, the one beneficial adipokine goes down).
- TNF-α, IL-6 — pro-inflammatory cytokines. Levels are increased in obesity → chronic low-grade inflammation → insulin resistance, endothelial dysfunction.
- Resistin — promotes insulin resistance.
- PAI-1 — promotes thrombosis.
"Long-term signals of energy stores and short-term fluctuations in food intake are released from adipose tissues and the gut endocrine system. These signals are integrated in the hypothalamus and brainstem and modulate neuropeptide release, resulting in subsequent changes in appetite, behaviour and energy expenditure to maintain a stable weight." [1]
"Physiological adaptations (e.g. increase in appetite-stimulating hormones like ghrelin and decrease in appetite-suppressing hormones) to defend against weight loss." [1]
In plain English: When you lose weight, your body fights back:
- Ghrelin (the "hunger hormone" from the stomach) goes UP.
- Leptin, PYY, GLP-1 go DOWN.
- Basal metabolic rate decreases (adaptive thermogenesis).
- The net effect: you feel hungrier, you burn fewer calories, and your body physiologically drives you back towards your previous weight set-point.
This is why regain is common after weight loss and why obesity should be managed as a chronic relapsing disease, with continuing behavioural support and, where appropriate, long-term medication or metabolic surgery—not as a short course followed by discharge.
7. Management of Obesity
Management aims: [1]
- Weight reduction
- Maintenance of weight loss
- Modification of concurrent risk factors for mortality and morbidity such as smoking, diabetes, hypertension and hyperlipidaemia
- BE REALISTIC. Treatment directed towards health rather than cosmetic goals
- Weight loss of 5–10% of total body weight is already associated with health benefit
High Yield — The 5–10% Rule
Strategies for weight reduction: [1]
- Set a realistic goal
- Lifestyle modification — diet and exercise
- Drug therapy
- Surgery
"Cornerstone of any treatment program for obesity." [1]
| Diet Type | Definition | Key Points |
|---|---|---|
| LCD (Low-Calorie Diet) | ≥ 800 kcal/d, typically 800–1500 kcal/d | Standard approach |
| VLCD (Very Low-Calorie Diet) | < 800 kcal/d | Faster initial weight loss but NOT superior for maintenance at 1 year. Should only be used under medical supervision. |
Key facts:
- The slide proposes around 0.5 kg/week from a roughly 600 kcal/day deficit. [1] Treat this as a pragmatic starting target, not a physiological law.
- Faster loss can increase lean-mass loss, gallstone risk and nutritional problems, but supervised total-diet-replacement or post-operative programmes may appropriately produce faster loss. Adequate protein and resistance exercise help preserve lean mass.
- VLCD leads to faster rate in weight reduction in first 2–3 months but NOT superior in maintenance of weight loss after 1 year. [1]
- Long-term weight loss in most trials (FU 2–7 years): weight loss in the range of 2 to 6 kg — this is sobering and underscores why diet alone is insufficient for severe obesity. [1]
- Diet therapy effective in promoting significant weight loss (max 4–7%). [1]
- Low carbohydrate diets are somewhat more effective in the short term (3–6 months). [1]
- All diets appear equivalent over the long term (1 year or longer). [1]
Clinical implication: The "best" diet is the one the patient can adhere to long-term. Whether it's low-carb, low-fat, Mediterranean, or DASH — compliance matters more than macronutrient composition.
For people with diabetes, avoid a fixed universal macronutrient prescription. Use individualised medical nutrition therapy that accounts for glucose-lowering drugs, kidney function, culture, eating pattern and goals; adjust hypoglycaemia-producing medicines when intake falls substantially.
"Combining dietary modification with adequate physical activity has been repeatedly shown to be important for initial weight loss and NECESSARY for long-term weight maintenance." [1]
"Gradual increase physical activity until energy expenditure of 1000 to 1500 kcal/week." [1]
Why activity matters even without major weight loss: it improves cardiorespiratory fitness, insulin sensitivity, blood pressure, mood and function, helps preserve lean mass, and supports weight maintenance. It does not completely prevent adaptive reductions in energy expenditure.
The lecture's 1000–1500 kcal/week is difficult to estimate reliably person-to-person. A more usable public-health prescription is to build towards 150–300 minutes/week of moderate aerobic activity (or 75–150 minutes vigorous) plus muscle-strengthening activity on at least 2 days/week, adapted to mobility, symptoms and baseline fitness. [14]
7.5 Drug Therapy
The lecture frames medication as an adjunct after inadequate response to lifestyle treatment. [1]
Indications: BMI > 30, OR BMI 27–29 with comorbidities. [1]
Continue only while benefit outweighs harm, reassessing efficacy, tolerability, comorbidities, pregnancy plans, access and adherence.
Anti-obesity medication is generally long-term chronic-disease treatment, not a short “course.” Selection should be individualised rather than simply choosing the drug with the largest headline percentage. Current US guidance ranks semaglutide and tirzepatide as first-line pharmacological options for many non-pregnant adults with obesity, but local approval and access must be checked. [15]
| Agent | Mechanism | Lecture/trial weight-loss context | Key safety points | Status/context |
|---|---|---|---|---|
| Orlistat | Gastric/pancreatic lipase inhibitor | Slide: ~2.9–3.4% or kg | Oily stool/urgency; fat-soluble vitamin and drug-absorption issues | Older oral option |
| Phentermine/topiramate ER | Sympathomimetic appetite suppression plus topiramate | Slide: ~6.6–8.6% | Teratogenic; HR/BP, mood/cognition, acidosis and stone risk | Approval/availability varies by jurisdiction; “not yet in HK” is a 2023 slide statement |
| Naltrexone/bupropion ER | Opioid antagonism plus dopamine/NE reuptake inhibition | Slide: ~4.8% | Avoid with seizure disorder, uncontrolled hypertension or chronic opioid use; pregnancy contraindicated | Approval/availability varies |
| Liraglutide | GLP-1 receptor agonist | Slide: ~5.4% | GI effects, gallbladder disease and pancreatitis warning; daily injection | Weight-management dose differs from diabetes dose |
| Semaglutide | GLP-1 receptor agonist | Slide: ~15% in the cited trial programme | GI effects, gallbladder/pancreatitis warnings; contraindicated with personal/family MTC or MEN2 | The slide reflects the 2021 injectable approval; current formulations/indications are broader [17] |
| Tirzepatide | Dual GIP/GLP-1 receptor agonist | FDA pivotal trial without diabetes: ~18% mean loss at 15 mg at 72 weeks | Similar GI and gallbladder/pancreatitis precautions; contraindicated with personal/family MTC or MEN2 | FDA-approved for chronic weight management in 2023; absent from this 2023 lecture deck [16] |
| Drug | Mechanism | Reason for Withdrawal | Year |
|---|---|---|---|
| Rimonabant | Endocannabinoid receptor (CB1) antagonist | Psychiatric side effects (depression, suicidality) | 2008 |
| Sibutramine | Serotonergic agent (SNRI) | ↑ CV events (MI, stroke) — SCOUT trial | 2010 |
| Lorcaserin | Selective 5-HT2C receptor agonist | ↑ Cancer risk | 2020 |
Orlistat:
"A gastrointestinal lipase inhibitor. Promotes weight loss by inhibiting gastrointestinal lipase and thus lowering absorption of dietary fat. Decreases dietary fat absorption by 30% with a dose of 120 mg three times a day. Systemic absorption is negligible. Possible side effects: GI upset, steatorrhoea, decreased absorption of fat-soluble vitamins." [1]
- Why steatorrhoea: Unabsorbed fat passes through → oily/fatty stools, flatulence, faecal urgency. This actually serves as a behavioural reinforcement — if patients eat a high-fat meal, the GI symptoms are worse, encouraging low-fat eating.
- Clinical pearl: Supplement fat-soluble vitamins (A, D, E, K) separately, taken 2 hours apart from orlistat.
Liraglutide (Saxenda):
"GLP-1 receptor agonist. Enhances glucose-stimulated insulin secretion and reduces glucagon secretion, delays gastric emptying and increases satiety by central effects on the hypothalamus. A higher dose formulation developed specifically for the treatment of obesity (3 mg/day, subcutaneous injection)." [1]
- Formulation caveat: the lecture describes liraglutide injection. Peptide delivery is usually injectable, but semaglutide formulations and indications have evolved; prescribe the approved weight-management product and label for the jurisdiction, not an assumed diabetes-dose substitution. [17]
- Dual benefit: If the patient also has T2DM, a GLP-1 RA treats both conditions simultaneously.
Semaglutide (Wegovy):
"GLP-1 analogue, 94% homology to human GLP-1. Half-life approximately 1 week → can be given as a weekly injection. Approved for Type 2 DM at 1 mg weekly. High dose of 2.4 mg weekly approved by FDA for treatment of obesity in June 2021. Mean weight loss approximately 15%. Side effects: mainly gastrointestinal." [1]
- How to interpret ~15%: this is a trial mean, not a guaranteed individual response and not a direct comparison with surgery or another drug. Outcomes depend on population, adherence, duration and estimand; weight regain commonly follows withdrawal, supporting chronic treatment when effective and tolerated.
Phentermine/Topiramate (Qsymia):
"Phentermine — anorexigenic agent, acts via enhancement of norepinephrine release and possibly blockade of norepinephrine reuptake. Topiramate — neurostabiliser for seizures and migraine prophylaxis, exact mechanism for weight loss not known. Amount of weight loss achieved with combination > either agent alone." [1] "Adverse events: teratogenicity, slight increase in heart rate, psychiatric and cognitive adverse effects, metabolic acidosis." [1]
- Teratogenicity: Topiramate is associated with oral cleft defects → pregnancy testing and effective contraception are essential. Check current Hong Kong registration/formulary status rather than relying on the slide's 2023 “not available” statement.
Bupropion/Naltrexone (Contrave):
"Bupropion (inhibitor of neuronal reuptake of dopamine and norepinephrine) — also used as antidepressant and smoking cessation aid. Naltrexone (opioid antagonist) — also used for alcohol/opioid dependence. Reduces appetite and food cravings." [1] "Side effects: nausea, constipation, headache, vomiting, dizziness, insomnia, dry mouth, diarrhoea. Monitor for mood changes, suicidal thoughts or actions." [1]
- Why the combination works: Bupropion stimulates POMC neurons → releases α-MSH (appetite suppression). But POMC neurons also release β-endorphin, which feeds back to inhibit further POMC firing. Naltrexone blocks this opioid auto-inhibition → sustained POMC activation → sustained appetite suppression.
Safety — incretin-based anti-obesity drugs
Semaglutide and tirzepatide require gradual dose escalation and review for persistent severe GI symptoms, dehydration/acute kidney injury, gallbladder disease and pancreatitis symptoms. Do not combine tirzepatide with another GLP-1 receptor agonist. They are not used in pregnancy, and product labels contraindicate use with personal/family medullary thyroid carcinoma or MEN2. [16][17]
7.6 Bariatric Surgery
The slide reproduces the historical 1991 NIH thresholds: [1]
- BMI ≥ 40 kg/m² without comorbidity
- BMI ≥ 35 kg/m² with comorbidity (e.g. diabetes, respiratory insufficiency)
Current correction — metabolic/bariatric surgery thresholds
The slide thresholds are historically important but no longer represent the 2022 ASMBS/IFSO indications. Current guidance recommends metabolic/bariatric surgery for BMI ≥35 kg/m² regardless of comorbidity, considers it for BMI 30.0–34.9 kg/m² with metabolic disease or inadequate durable response to non-surgical treatment, and adjusts thresholds for Asian populations: BMI > 25 suggests clinical obesity and BMI > 27.5 should be offered surgery. Local service criteria and multidisciplinary assessment still apply. [18]
"Reduce the size of reservoir/intake" and/or "Reduce the efficacy of absorption." [1]
| Procedure | Mechanism | Key Features |
|---|---|---|
| Intragastric balloon | Endoscopically placed space-occupying balloon; promotes early satiety and may delay gastric emptying | Temporary and reversible, but it is a medical device—not merely “behavioural therapy” |
| Adjustable gastric banding (AGB) | Inflatable band creates a small proximal pouch; restriction is altered through a tube connected to a subcutaneous access port | Reversible but less durable weight loss and more late revision/removal; use has declined substantially [18] |
| Sleeve gastrectomy (SG) | Longitudinal resection along the greater curvature leaves a narrow gastric tube while preserving pylorus and intestinal continuity | No intestinal bypass, but effects are not purely restrictive; altered gastric emptying and gut-hormone signalling contribute. Reflux can worsen |
| Roux-en-Y gastric bypass (RYGB) | Small proximal gastric pouch is anastomosed to jejunum; excluded stomach/duodenum carry biliopancreatic secretions to a downstream jejunojejunostomy | Restriction plus altered nutrient flow/hormonal signalling and some malabsorption; dumping, marginal ulcer, internal hernia and micronutrient deficiency are important |
| Biliopancreatic diversion with duodenal switch (BPD/DS) | Sleeve plus long intestinal bypass, separating alimentary and biliopancreatic limbs until a short common channel | The comparison diagram shows greatest average loss but also the greatest malabsorption/protein and fat-soluble-vitamin risk; requires expert selection and intensive lifelong follow-up |
Reading the operative diagrams: [1]
- Balloon: the sequence shows endoscopic delivery of a collapsed balloon, intragastric inflation and final space occupation; it does not resect or bypass tissue.
- Band: identify the ring around the gastric cardia, connecting tubing and subcutaneous port—the port permits percutaneous volume adjustment.
- Sleeve: the vertical staple line marks removal of most of the greater-curvature stomach; the pylorus and small bowel remain in continuity.
- RYGB: food passes from the small pouch directly into the Roux/alimentary limb, while bile and pancreatic secretions travel through the excluded stomach/duodenum and biliopancreatic limb before meeting at the jejunojejunostomy.
- BPD/DS: the sleeve empties into distal small bowel; the very long bypass explains both greater weight loss and greater nutritional risk.
Intragastric balloon red flags
Severe abdominal/back pain, persistent vomiting, distension or dyspnoea after a liquid-filled intragastric balloon requires urgent assessment for obstruction, perforation, spontaneous hyperinflation or acute pancreatitis; premature removal may be required. [19]
Key lecture points on comparison: [1]
- AGB: lower mortality and complication rates BUT higher reoperation rate and less substantial weight loss than GB.
- Gastric bypass: more effective in weight loss but associated with more complications.
- Sleeve gastrectomy: more effective in weight loss than AGB and comparable to GB.
These comparisons are cohort- and time-dependent, not a universal ranking. The visual slide itself shows increasing average weight loss from band → sleeve → RYGB → BPD/DS. Sleeve and RYGB now account for about 90% of operations worldwide; AGB use has fallen markedly. [18]
"Mean 20-year weight reduction in the large Swedish Obese Subjects' study was 25% for Roux-en-Y gastric bypass and 15% for adjustable gastric banding." [1]
"An effective means to achieving lasting weight loss and improving metabolic disease and reducing cardiovascular risk in selected candidates." [1]
"Pre-op multi-disciplinary assessment is needed to select the appropriate candidates." [1]
"Choice of surgical modality should take individual goals and existing comorbidities into account." [1]
"Long-term follow-up is mandatory to support a safe outcome." [1]
The slide quotes adverse intraoperative events of ~5% from an older 10-site US cohort. [1] This is not a universal contemporary risk estimate; current ASMBS/IFSO guidance reports perioperative mortality around 0.03–0.2%, while morbidity varies by procedure and patient factors. [18]
Long-term complications include:
- Nutritional deficiencies (especially after RYGB): iron, B12, folate, calcium, vitamin D, fat-soluble vitamins — due to bypassed duodenum/proximal jejunum where these are absorbed.
- Dumping syndrome (after RYGB): rapid gastric emptying → osmotic fluid shifts → nausea, cramping, diarrhoea, vasomotor symptoms.
- Anastomotic leak/stricture.
- Internal hernias (after RYGB).
- Gallstone formation (rapid weight loss → ↑ cholesterol saturation of bile).
- Band slippage/erosion (AGB-specific).
- GORD can worsen after sleeve gastrectomy.
The complication table adds procedure-specific recognition points: late AGB problems include slippage, port/tubing leakage and erosion; bypass problems include anastomotic stricture, marginal ulcer and bowel obstruction/internal hernia. Its quoted nutritional-deficiency percentages come from older cohorts and should not be treated as contemporary universal rates, but the pattern is durable: iron, B12, calcium and vitamin D require lifelong surveillance, with even greater protein and fat-soluble-vitamin risk after BPD/DS. [1]
The NCEP ATP III (2005) definition of metabolic syndrome is frequently tested alongside obesity: [2]
≥ 3 out of 5 criteria:
| Criterion | Threshold |
|---|---|
| Central obesity (WC) | ≥ 102 cm (M) / ≥ 88 cm (F) in the original ATP III definition; use ethnic-specific thresholds where adopted |
| Fasting glucose | ≥ 5.6 mmol/L (100 mg/dL) or on treatment |
| Triglycerides | ≥ 1.7 mmol/L or on treatment |
| HDL-C | < 1.034 mmol/L (M) / < 1.293 mmol/L (F) or on treatment |
| Blood pressure | ≥ 130 mmHg SBP or ≥ 85 mmHg DBP, or on treatment |
- OSA (GC 024): Obesity is the most important modifiable risk factor for OSA. A BMI 24 with normal sleep quality but fatigue/snoring → look for non-sleep-related causes first (see 2024 MCQ Q39). [4][8]
- CKD (GC 034): Obesity is a CKD risk factor → recommend eGFR testing in overweight/obese patients. [9]
- Gallstones: "Fat, Female, Forty, Fertile" — 2021 MCQ Q81 tests gallstone imaging in obese female. [5][10]
- MASLD (GC 240): Obesity → insulin resistance → hepatic steatosis. [6]
- Cushing's syndrome: The exam loves asking you to differentiate Cushing's from simple obesity. Key discriminators: thin skin, proximal myopathy, purple striae, easy bruising (catabolic features) are present in Cushing's but NOT in simple obesity. [3]
- VTE in pregnancy: Maternal obesity is a risk factor for venous thromboembolism → LMWH prophylaxis considerations (2025 MCQ Q10). [11]
- Familial hypercholesterolaemia: While not "obesity" per se, hyperlipidaemia management overlaps. Dutch criteria for FH diagnosis are important. [12]
10. Clinical Approach Summary
- Duration and trajectory of weight gain
- Diet and exercise habits (24-hour dietary recall)
- Psychiatric history: depression, binge eating disorder
- Medication review (drug-induced weight gain)
- Symptoms of secondary causes: fatigue/cold intolerance (hypothyroidism), striae/weakness (Cushing's), menstrual irregularity (PCOS), headache/visual field defects (hypothalamic tumour)
- Screen for complications: chest pain, dyspnoea, snoring, daytime sleepiness, polyuria/polydipsia, joint pain
- Family history of obesity, DM, CVD
- Psychosocial: self-esteem, motivation for change, socioeconomic factors
- Vitals: BP (HTN), HR
- Anthropometry: Weight, height, BMI, waist circumference
- Endocrine stigmata: Moon face, buffalo hump, striae (Cushing's); thyroid enlargement; acanthosis nigricans (insulin resistance); hirsutism/acne (PCOS)
- Cardiovascular: Signs of heart failure
- Respiratory: Mallampati score (OSA risk)
- Abdominal: Hepatomegaly (MASLD), hernias
- Skin: Acanthosis nigricans, intertrigo, skin tags
- MSK: Joint tenderness (OA)
- Routine cardiometabolic assessment: FPG/HbA1c, lipid profile, liver enzymes and renal function according to age, BMI and comorbidity; assess BP directly rather than relying on a laboratory “screen”
- Targeted endocrine testing: TSH when clinically indicated; if Cushing syndrome is genuinely suspected, use a validated initial test (1-mg overnight dexamethasone suppression, late-night salivary cortisol or 24-hour urinary free cortisol) rather than indiscriminate cortisol measurement
- Urine: uACR when diabetes, hypertension or CKD risk warrants it
- Sleep study: If symptoms suggest OSA
- Liver/gallbladder assessment: image for a clinical indication, not simply because BMI is elevated; if MASLD risk is present, liver-fibrosis risk stratification is more useful than documenting steatosis alone
- Body composition imaging: DEXA is not required to diagnose or routinely manage obesity
Active Recall - I Am Overweight, Doctor
High Yield Summary
- Use the correct framework: Hong Kong adults are classified as overweight at BMI 23.0–24.9 and obese at ≥25, while WHO's 23/27.5 values were risk action points rather than a universal Asian classification.
- Central adiposity adds risk information: Chinese waist thresholds in the slide are ≥90 cm for men and ≥80 cm for women.
- Assess health, not appearance: complications include T2DM, hypertension/CVD, dyslipidaemia, MASLD, OSA, reproductive disease, OA and mental-health burden.
- Look selectively for contributors: medication review is routine; endocrine testing is guided by clinical features rather than a blanket panel.
- Treat obesity as chronic disease: nutrition, physical activity, sleep and behavioural support continue alongside medication or surgery; 5–10% loss is already clinically meaningful.
- Medication is individualised and usually long-term: semaglutide and tirzepatide are current high-efficacy options, but contraindications, comorbidities, pregnancy plans, access and patient preference determine choice.
- Know historical withdrawals: rimonabant—psychiatric harm; sibutramine—cardiovascular harm; lorcaserin—cancer signal.
- Read the surgical anatomy: band = adjustable port; sleeve = longitudinal gastrectomy with intact bowel; RYGB = small pouch plus Roux limb; BPD/DS = longest bypass and greatest nutritional risk.
- Do not quote 1991 surgical thresholds as current: 2022 ASMBS/IFSO recommends surgery at BMI ≥35 regardless of comorbidity and uses lower thresholds for Asian populations.
- Long-term follow-up is essential for weight recurrence, medication adverse effects, nutritional deficiencies and procedure-specific complications.
[1] Lecture slides: GC 064. I am overweight, doctor.pdf (all pages) [2] Senior notes: Ryan Ho Endocrine.pdf (p.116 — BMI classification table, metabolic syndrome definition) [3] Past papers: 2022 Fourth Summative MCQ.pdf (Q9 — Cushing syndrome vs obesity) [4] Past papers: 2024 Fourth Summative MCQ.pdf (Q39 — fatigue/sleepiness in normal-BMI patient, OSA vs non-sleep causes) [5] Senior notes: Block A - Upper abdominal pain_ peptic ulcer; pancreatitis and gallstone.pdf (p.26 — gallstone risk factors including obesity) [6] Lecture slides: GC 240. MASLD and Alcoholic Liver Disease.pdf (MASLD link to obesity) [7] Senior notes: Block A - Deterioration of eyesight in a diabetic patient_ diabetic complications.pdf (p.12 — dietary management in DM) [8] Lecture slides: GC 024. A Fatigued and Sleepy Patient.pdf [9] Senior notes: Block A - Chronic Kidney Disease and its Complications.pdf (p.10 — obesity as CKD risk factor) [10] Past papers: 2021 Fourth Summative Assessment MCQ.pdf (Q81 — gallstones in obese female) [11] Senior notes: Block A - Leg swelling and chest pain_ deep vein thrombosis; pulmonary embolism; Thrombophilia.pdf (p.19 — maternal obesity as VTE risk factor) [12] Senior notes: Introduction to Clinical pharmacology (I) (Pharmaco- Genomics, Precision Medicine).pdf (p.2 — FH, Dutch criteria) [13] Hong Kong Department of Health Population Health Survey 2020–22, Part II. [14] WHO guidelines on physical activity and sedentary behaviour: at a glance. [15] American College of Physicians living clinical guideline: pharmacologic treatments with lifestyle modifications in nonpregnant adults with overweight or obesity (2026). [16] US FDA: approval and prescribing context for tirzepatide (Zepbound) for chronic weight management. [17] US FDA prescribing information for semaglutide (Wegovy), 2026 label. [18] 2022 ASMBS/IFSO indications for metabolic and bariatric surgery. [19] US FDA: weight-loss and weight-management devices, including intragastric-balloon safety signals.
GC063 I Am Losing Weight And Sweating All The Time
A clinical presentation characterized by unintentional weight loss and excessive sweating, commonly suggesting hyperthyroidism, malignancy, chronic infection, or other hypermetabolic or systemic conditions requiring urgent evaluation.
GC065 I Have An Itchy Rash
A clinical presentation of pruritic dermatitis requiring systematic evaluation to distinguish among common causes such as eczema, contact dermatitis, urticaria, fungal infections, and scabies.