Obesity Medical Management
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Direct answer
Obesity is a chronic disease defined by body mass index, and in South Asians the cut-offs are lower than WHO's standard thresholds because diabetes and hypertension appear at a lower BMI. Management starts with a structured lifestyle programme. Anti-obesity drugs or bariatric surgery follow when weight loss is inadequate or comorbidity is significant.
What you must remember
- Asian BMI cut-offs: Indian consensus statements commonly use overweight from about 23 kg/m2 and obesity from about 25 kg/m2, with 27.5 kg/m2 marking high risk, against WHO's 25 and 30.
- Waist circumference: central obesity in South Asian adults is commonly taken as at least 90 cm in men and 80 cm in women.
- First-line treatment: diet change, at least 150 minutes of moderate activity weekly and a target of 5 to 10 percent weight loss, which already improves glycaemia and blood pressure.
- Pharmacotherapy: orlistat needs fat-soluble vitamin supplementation, phentermine with topiramate is limited by pregnancy and cardiovascular risk, and GLP-1 receptor agonists such as liraglutide and semaglutide are widely used.
- Absolute contraindication: personal or family history of medullary thyroid carcinoma or MEN type 2 excludes GLP-1 receptor agonists.
- Bariatric criteria: classically BMI of 40 or more, or 35 or more with serious comorbidity; newer ASMBS and IFSO guidance offers surgery from 35 regardless of comorbidity, and Asian guidance lowers the threshold further, especially with diabetes.
- Secondary obesity: check thyroid function, cortisol excess, hypothalamic disease and drugs such as steroids and antipsychotics before attributing weight gain to lifestyle alone.
Worked example: a 46-year-old with rising weight and diabetes
A 46-year-old man has a BMI of 31, a waist of 98 cm, hypertension and an HbA1c of 7.2 percent. The plan moves in stages, with each review deciding the next step.
- Confirm and screen: The measurements are confirmed and secondary causes are screened, starting with TSH and a morning cortisol if features suggest excess.
- Start lifestyle change: A structured lifestyle programme with a dietitian is set, with review at about three months.
- Add pharmacotherapy if weight loss stalls: If weight has fallen by less than 5 percent by then, pharmacotherapy is added, and with diabetes a GLP-1 receptor agonist is a reasonable choice after the contraindications are excluded.
- Reassess at six to twelve months: Weight and comorbidity are reassessed then. If BMI rises to 35 or more with diabetes despite these measures, metabolic surgery is discussed.
- Consider the surgical options: Sleeve gastrectomy and Roux-en-Y gastric bypass are the commonest procedures, and both often induce remission of type 2 diabetes.
- Aim for sustained loss: The aim is sustained loss rather than a single rapid result, because weight regain after stopping drugs is common.
Where the examiner tests your numbers
The commonest errors involve numbers and drug safety.
- Trap: using WHO's BMI thresholds for an Indian patient Correct: Indian cut-offs flag risk from BMI 23 and obesity from 25, which WHO's thresholds miss.
- Trap: prescribing orlistat without a plan for vitamins Correct: its fat malabsorption demands fat-soluble vitamin supplementation, while sibutramine is historical and withdrawn.
- Trap: prescribing phentermine casually Correct: it is sympathomimetic, so pregnancy, cardiovascular disease, hyperthyroidism and glaucoma exclude it.
- Trap: using metformin as an obesity drug Correct: it is not licensed for obesity alone in non-diabetic patients, although it is used for insulin resistance.
The bariatric question tests whether comorbidity lowers the BMI threshold, and Asian guidance lowers it still.
Frequently asked questions
What BMI cut-off defines obesity in Indian adults?
Indian consensus statements commonly define obesity from a BMI of about 25 kg/m2, and overweight from about 23 kg/m2, against WHO's standard obesity threshold of 30 kg/m2. A BMI of 27.5 kg/m2 and above is treated as high risk for diabetes and cardiovascular disease.
Which anti-obesity drug is contraindicated in medullary thyroid carcinoma?
GLP-1 receptor agonists such as liraglutide and semaglutide are contraindicated in medullary thyroid carcinoma and in MEN type 2, because of a rodent signal of thyroid C-cell tumours. Personal or family history of these conditions must be asked before starting any agent in this class.
What are the criteria for bariatric surgery in obese adults?
Bariatric surgery has classically been offered for a BMI of 40 kg/m2 or more, or 35 kg/m2 or more with serious comorbidity such as type 2 diabetes or sleep apnoea. Newer guidance and Asian guidance lower these thresholds, and surgery is considered only after structured medical management has been tried.
Why is orlistat prescribed with vitamin supplements?
Orlistat blocks pancreatic lipase, so fat absorption falls and fat-soluble vitamins A, D, E and K can be lost in the stool. Supplements taken at least two hours from the drug are advised to prevent deficiency during orlistat treatment.
Which secondary causes must be excluded before treating obesity medically?
Hypothyroidism, Cushing syndrome, hypothalamic disease and drug-induced weight gain from steroids or antipsychotics must be excluded before treating obesity medically. Missing a secondary cause means drug therapy may fail.