Types of weight loss

Weight problems are classified by measurement and by cause - and the classification matters because South Asian bodies run into trouble at lower weights than Western charts suggest.

By BMI (with the Indian cut-offs that apply to us):

• Normal: 18.5-22.9
• Overweight: 23-24.9
• Obesity class I: 25-29.9
• Obesity class II: 30 and above (International cut-offs - 25 overweight, 30 obese - understate Indian risk; diabetes and heart disease appear at lower BMI in South Asians.)

By fat distribution. Abdominal (central, 'apple') obesity - fat around the belly and organs - is the dangerous pattern: it drives diabetes, fatty liver, cholesterol problems and heart disease. Peripheral ('pear') fat on hips and thighs is metabolically safer. Waist circumference (over 80 cm women, 90 cm men) and waist-to-hip ratio capture this better than weight alone. This is why a 'normal-weight' person with a big waist can be at higher risk than a heavier person with slim waist.

By cause:

• Primary (common) obesity: from lifestyle - the vast majority.
• Secondary obesity: from a medical condition (hypothyroidism, PCOS, Cushing's) or medicines (steroids, some psychiatric and diabetes drugs) - needs the cause treated.
• Monogenic and syndromic obesity: rare, usually from childhood.

By course: adult-onset gradual gain (the commonest), lifelong obesity from childhood (harder, needs earlier and stronger intervention), and weight cycling ('yo-yo') from repeated crash diets - which leaves people heavier and more frustrated each round.