BMI and Its Limitations
| BMI Category | Range | Limitations |
|---|---|---|
| Underweight | <18.5 | BMI doesn't distinguish fat from muscle |
| Normal | 18.5–24.9 | Doesn't indicate fat distribution |
| Overweight | 25–29.9 | Waist circumference better predicts metabolic risk |
| Obese class 1 | 30–34.9 | Lower BMI thresholds in South Asian populations |
| Obese class 2 | 35–39.9 | High metabolic and cardiovascular risk |
| Obese class 3 | ≥40 | Very high risk — consider bariatric referral |
Why Caloric Restriction Alone Fails Long-Term
- Adaptive thermogenesis — metabolism slows significantly with weight loss (~100–300 kcal/day)
- Hormonal changes — GLP-1 and peptide YY fall; ghrelin rises → increased hunger after weight loss
- Set point — the body actively defends its weight
- Muscle loss on aggressive restriction — reduces basal metabolic rate
- Psychological fatigue and food environment — undermines adherence
Evidence-Based Weight Loss Strategies
| Intervention | Expected Weight Loss | Evidence |
|---|---|---|
| Diet + behaviour change | 5–10% | Strong; best maintained with ongoing support |
| Exercise added to diet | Modest additional 2–3% — but preserves muscle, improves metabolic health | Strong |
| Very low calorie diet (800 kcal) | 12–15% at 1 year | Strong; NHS T2DM Path to Remission |
| Semaglutide (Wegovy 2.4 mg weekly) | ~15% | STEP trials — landmark |
| Tirzepatide (Mounjaro) | ~20–22% | SURMOUNT trials — best drug efficacy to date |
| Bariatric surgery (sleeve/bypass) | 25–35% | Most durable; reduces mortality 30–40% |
Exercise Prevents RegainExercise's primary role in weight management is not weight loss per se — it's weight maintenance and metabolic benefit. People who maintain weight loss long-term exercise regularly (~60 min/day). Weight regain without exercise is almost universal.
Does eating after 8pm cause weight gain?
Not directly. Total caloric intake over 24 hours — not timing — determines weight change. However, late eating is associated with poorer food choices and higher caloric intake. Intermittent fasting works largely by reducing eating windows and total intake.
How does semaglutide work for weight loss?
Semaglutide (GLP-1 agonist) acts on the brain's appetite centres, slowing gastric emptying and increasing satiety. People feel full sooner and less hungry between meals — naturally reducing caloric intake by 300–500 kcal/day on average.
Is bariatric surgery safe?
Bariatric surgery (gastric bypass, sleeve gastrectomy) has an operative mortality of ~0.1% — safer than gallbladder surgery. Long-term, it significantly reduces type 2 diabetes remission, cardiovascular events, and cancer risk. Suitable for BMI ≥40, or ≥35 with significant comorbidities.
Does stress cause weight gain?
Yes — via cortisol. Chronic stress raises cortisol, which increases visceral fat deposition, sugar and fat cravings, and emotional eating. Stress management (CBT, sleep, exercise) is therefore part of effective weight management.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.