Obesity Explained: Causes, Classes, Diagnosis & Management

Both can be correct — because India uses different BMI thresholds than the WHO’s standard Western population reference. Standard WHO global thresholds: Overweight = BMI 25-29.9; Obesity = BMI ≥30. Asian-specific thresholds (adopted by ICMR and WHO Asia-Pacific guidance): Overweight = BMI 23-27.4; Obesity = BMI ≥27.5. Why different? South Asians and East Asians accumulate more visceral (abdominal) fat at lower BMI values than Europeans — a BMI of 25 in an Indian person corresponds to a similar metabolic risk as a BMI of 30 in a European. This means cardiovascular risk, insulin resistance, and T2D risk are elevated at lower BMI in Indians. Practical implication: if your BMI is 27 and your waist circumference is above 90cm (men) or 80cm (women) — the ICMR threshold for Indian abdominal obesity — your risk profile is comparable to someone with Western-definition obesity. Indian doctors using ICMR-NIN 2024 or the Consensus for the Asian Indian phenotype will correctly flag this as obesity requiring intervention. If a doctor outside India uses WHO standard thresholds, they may classify the same patient differently. Bottom line: your Indian doctor’s classification at BMI 27 is medically appropriate and should inform treatment decisions.

Abdominal or visceral obesity is a stronger predictor of metabolic disease risk than BMI alone — because visceral fat (the fat stored around internal organs in the abdomen) is metabolically active in ways that subcutaneous fat (under the skin) is not. How visceral fat drives disease: it secretes pro-inflammatory cytokines (TNF-α, IL-6) that promote insulin resistance; it is adjacent to the liver’s portal circulation, directly impairing hepatic insulin clearance; it correlates more strongly with T2D, heart disease, NAFLD, and hypertension than BMI alone. The measurement: waist circumference, measured at the navel level with a tape measure (not breath held, not pushed in). Indian-specific cutoffs (ICMR / WHO Asia-Pacific 2000): High risk: men ≥90cm; women ≥80cm. These are lower than the 102cm/88cm Western thresholds. Another measure is the waist-to-height ratio (WHtR) — if your waist circumference is more than half your height in cm, visceral obesity risk is significantly elevated. Why this matters for treatment: a person with BMI 26 and waist 94cm has a worse metabolic risk profile than someone with BMI 32 and waist 88cm. This is why some Indian endocrinologists initiate pharmacological treatment at BMI 25+ when abdominal obesity and comorbidities are present — consistent with IDF Asia-Pacific diabetes risk guidelines. Self-check: use a fabric tape measure, measure at the navel level in the morning before eating, repeat 3 times for accuracy.

PCOS (Polycystic Ovary Syndrome) and obesity have a bidirectional relationship — each worsens the other. Roughly 40-80% of women with PCOS have overweight or obesity, with the highest rates in India. The mechanism: Obesity → PCOS: excess adipose tissue (especially visceral fat) amplifies insulin resistance → hyperinsulinaemia → drives the ovaries to produce excess androgens (testosterone) → disrupts the hypothalamic-pituitary-ovarian axis → irregular ovulation and menstrual cycles → PCOS phenotype. PCOS → Obesity: androgen excess promotes central fat distribution; insulin resistance directly impairs the body’s ability to use glucose, promoting fat storage; disrupted leptin signalling impairs satiety. The shared core: insulin resistance is the central mechanism. Any intervention that improves insulin sensitivity — whether dietary, pharmacological, or through weight loss — tends to improve both conditions simultaneously. Even 5-10% body weight reduction in PCOS women with obesity has been shown (Kiddy et al., Clin Endocrinol 1992; multiple subsequent RCTs) to: restore menstrual regularity in 55-60% of cases; improve ovulation rates; reduce androgen levels; lower T2D risk. Treatment approach in India: first-line for PCOS+obesity is lifestyle modification (1200-1500 kcal/day deficit diet with low GI foods + 150 min/week moderate activity); metformin is frequently added (improves insulin sensitivity, modest weight loss, reduces hyperandrogenism); inositol (myo-inositol + D-chiro-inositol 40:1) has accumulating evidence for PCOS + insulin resistance. Bariatric surgery for Class 3 PCOS+obesity has shown near-complete PCOS resolution in 75-90% of cases at 1-2 year follow-up. Consult a gynaecologist+endocrinologist team for combined PCOS-obesity management — one specialist alone is insufficient.

Bariatric surgery (weight-loss surgery) is widely available in India at NABH-accredited hospitals and is significantly more affordable than in Western countries. Common procedures: Laparoscopic Sleeve Gastrectomy (LSG): most common in India (~70% of bariatric procedures); stomach reduced to ~20% of original size; average excess weight loss 60-70% at 18 months. Roux-en-Y Gastric Bypass (RYGB): gold standard for T2D remission; redirects food to bypass most of stomach + part of small intestine; average excess weight loss 70-80% + T2D remission in 60-80% of cases. Eligibility criteria (IFSO / OSSI — Obesity and Metabolic Surgery Society of India guidelines): BMI ≥37.5 (Indian cutoff — lower than Western 40) without comorbidities; OR BMI ≥32.5 with serious comorbidities (T2D, hypertension, sleep apnea, PCOS, joint disease); age 18-65 (exceptions exist); failure of 6 months supervised lifestyle+medical therapy documented; psychiatric and nutritional clearance required. Cost in India (2026): Sleeve gastrectomy: ₹2.5-5 lakh at government/trust hospitals; ₹4-8 lakh at private NABH hospitals in metro cities. Gastric bypass: ₹4-7 lakh at government/trust hospitals; ₹6-10 lakh at private hospitals. Compared to: UK: £8,000-15,000; USA: $20,000-35,000. Insurance coverage: as of 2026, IRDAI has mandated that bariatric surgery for morbid obesity (BMI ≥40 or BMI ≥35 with comorbidities) is NOT explicitly excluded from standard health insurance policies, but most policies still require prior authorisation and medical necessity documentation. Government Ayushman Bharat PMJAY: does cover bariatric surgery for eligible beneficiaries at empanelled hospitals — check via the Ayushman Bharat portal or call 14555. Ideal referral pathway: endocrinologist + bariatric surgeon + clinical psychologist + registered dietitian — minimum 4-specialist team for optimal outcomes.