OBESITY

20-Mark Answer | MPT Level (Master of Physiotherapy)

Definition and Terminology

• Men with body fat >25% and women with body fat >35% are classified as obese.
• Borderline obese: men 20-25%, women 30-35%.
• The higher threshold for women accounts for sex-specific fat deposits (breast, hip, buttocks, thighs).

Classification - Body Mass Index (BMI)

Prevalence

• Globally: >1.9 billion adults are overweight; 650 million are obese (WHO).
• India: >135 million affected. Prevalence of obesity ranges from 11.8% to 16.9% (ICMR-INDIAB 2015).
• Higher prevalence in urban populations, high socioeconomic strata, and South India.
• In the USA: >70% of men and >64% of women are overweight/obese.
• Childhood obesity has tripled in the past 30 years - a major concern for future disease burden.

Pattern of Obesity (Fat Distribution)

Etiology of Obesity

1. Hormonal imbalances - endocrine gland dysfunction
2. Genetic factors - children with one or both obese parents carry more than twice the normal risk of becoming obese adults; body composition in prepubertal girls correlates with parental body composition
3. Gluttony / overeating - excess caloric intake beyond expenditure
4. Environmental and cultural factors - fast food access, food packaging, social norms
5. Inadequate physical activity - sedentary lifestyle
6. Emotional and psychological trauma
7. Alterations in homeostatic mechanisms - set point dysregulation
8. Variations in resting metabolic rate (RMR), diet-induced thermogenesis, and spontaneous activity ("fidgeting")
9. Viral susceptibility, cellular enzyme levels (lipoprotein lipase, ATPase), and brown adipose tissue activity

Pathophysiology and Control of Body Weight

1. Resting Metabolic Rate (RMR) / Basal Metabolic Rate (BMR)

• Accounts for 60-75% of total daily energy expenditure.
• Represents the minimum energy needed to sustain basic physiological processes.
• Decreases by 20-30% within weeks of fasting or very low calorie dieting - the body conserves energy stores.

2. Thermic Effect of a Meal (TEM)

• Energy expended during digestion, absorption, transport, metabolism, and storage of ingested food.
• Accounts for approximately 10% of daily energy expenditure.
• May be defective in obese individuals - impaired energy-wastage leads to caloric surplus.

3. Thermic Effect of Activity (TEA)

• Energy expended above RMR during any physical task or activity.
• Even small activities (fidgeting) contribute to TEA.
• All three components are regulated by the sympathetic nervous system.

Set Point Theory

Hormonal Mechanisms

Leptin (the "satiety hormone")

• Derived from Greek leptos = "thin."
• Produced by adipose cells and small intestinal enterocytes; acts on the hypothalamus to inhibit hunger and reduce fat storage.
• Weight gain raises leptin; weight loss reduces it.
• Leptin insensitivity (similar to insulin resistance): in obesity, cells cannot detect satiety despite high leptin levels and high energy stores - resulting in continued overeating.
• Congenital absence of leptin causes continuous hunger and marked obesity in children.

Ghrelin (the "hunger hormone")

• Produced by enteroendocrine cells of the stomach and GI tract.
• Increases food intake, stimulates gastric motility and acid secretion.
• Levels peak before meals and fall after eating.
• Hyperactivation of ghrelin contributes to overeating in obesity.

Uncoupling Protein-2 (UCP2) Gene

• High activity of UCP2 burns excess calories as heat without coupling to other energy processes (futile metabolism), thereby blunting excess fat storage.
• Reduced UCP2 activity may predispose to fat accumulation.

Health Problems Associated with Obesity

Cardiovascular and Metabolic

• Coronary heart disease, hypertension, stroke, atherosclerosis
• Type 2 diabetes (non-insulin-dependent) - obesity is the primary precipitant
• Elevated blood lipids (dyslipidemia)

Respiratory

• Sleep apnea
• Elevated blood CO₂ (hypercapnia) causing lethargy
• Polycythemia (compensatory increase in RBC production due to hypoxia)
• Abnormal clotting (thrombosis), cardiac enlargement, congestive heart failure

Other Systemic Conditions

• Certain cancers: endometrial, breast, colon
• Liver and gallbladder disease
• Osteoarthritis (increased mechanical load on joints)
• Varicose veins
• Reduced exercise tolerance (due to both respiratory compromise and excess body mass)

Psychological Effects

• Social stigma, depression, anxiety
• Body image disturbances
• Emotional eating cycles

Childhood Obesity

• Estimated 42 million children under age 5 were overweight in 2010.
• Prevalence (age 6-11): increased from 6.5% to 19.6%; (age 12-19): from 5.0% to 18.1%.
• Linked to sedentary lifestyle, fast food and soft drink consumption (contributing ~188 kcal/day extra), and home food environment.
• Childhood obesity is a stronger predictor of adult disease than obesity beginning in adulthood.
• Genetic predisposition plays a role but environment, behavior, and dietary access are modifiable factors.

Principles of Management

1. Diet and Caloric Restriction

• Weight loss should not exceed 0.45-0.9 kg (1-2 lb) per week.
• Reduce caloric intake by 250-500 kcal/day combined with low-fat, low-simple-sugar food choices.
• WHO recommends at least 400 g of fruits and vegetables daily to prevent obesity-related non-communicable diseases.

2. Special and Extreme Diets

• Ketogenic diets: restrict carbohydrates, generate ketone bodies (appetite suppression), but high in saturated fat and cholesterol.
• High-protein diets: short-term effectiveness only; risks include liver/kidney strain, dehydration, electrolyte imbalance, glycogen depletion, and lean tissue loss.
• Very Low Calorie Diets (VLCD): reserved for severe obesity (body fat >40-50%); requires close hospital supervision; rapidly depletes glycogen stores and impairs physical capacity.

3. Exercise and Physical Activity

• Exercise increases TEA and RMR, improves insulin sensitivity, and maintains lean body mass during weight loss.
• Combined diet + exercise is more effective and sustainable than either alone.

4. Behavior Modification Therapy

• One of the most effective long-term methods as results are permanent and easily integrated into daily life.
• Techniques include stimulus control (e.g., eating in only one location), portion control (single servings, no second helpings), self-monitoring, and addressing emotional eating patterns.

5. Pharmacotherapy

• Appetite suppressants and drugs that increase RMR have been used.
• Significant side effects including life-threatening complications limit their use.

6. Surgical (Bariatric) Treatment

• Reserved as a last resort when all other treatments fail and obesity is life-threatening.
• Gastric bypass and gastric banding/stapling are the most common procedures - restrict food entering the stomach.
• Highly effective but expensive; mortality risk: 1-2%.
• Intestinal bypass (surgically bypassing a large segment of small intestine) is now rarely used due to complications.

Disordered Eating (Obesity-Related Spectrum)

Summary

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Recent Research Papers: Obesity & Physiotherapy Interventions

TIER 1 - Systematic Reviews & Meta-Analyses (Highest Evidence)

Chen X, He H, Xie K et al. (2024) "Effects of various exercise types on visceral adipose tissue in individuals with overweight and obesity: A systematic review and network meta-analysis of 84 randomized controlled trials." Obes Rev, 2024 Mar | PMID: 38031812

• Analysed 84 RCTs to compare aerobic, resistance, combined, and HIIT exercise on visceral fat.
• Key finding: Combined aerobic + resistance training was most effective at reducing visceral adipose tissue.
• Directly relevant to physiotherapy prescription for obese patients.

Al-Mhanna SB, Batrakoulis A et al. (2024) "Effects of combined aerobic and resistance training on glycemic control, blood pressure, inflammation, cardiorespiratory fitness and quality of life in patients with type 2 diabetes and overweight/obesity." PeerJ, 2024 | PMID: 38887616

• Combined training significantly improved HbA1c, blood pressure, inflammatory markers (CRP), VO2 max, and quality of life.
• Strongly supports combined exercise as a first-line physiotherapy intervention.

Jayedi A, Soltani S, Emadi A et al. (2024) "Aerobic Exercise and Weight Loss in Adults: A Systematic Review and Dose-Response Meta-Analysis." JAMA Netw Open, 2024 Dec | PMID: 39724371

• Established a dose-response relationship between aerobic exercise volume and weight loss in adults.
• Provides guidance on exercise prescription thresholds for meaningful weight reduction.

Liu X, Li Q, Lu F et al. (2024) "Effects of aerobic exercise combined with resistance training on body composition and metabolic health in children and adolescents with overweight or obesity." Front Public Health, 2024 | PMID: 39185113

• Combined exercise reduced body fat %, BMI, waist circumference, and improved metabolic markers in youth.
• Highly relevant given the alarming rise in childhood obesity.

Eglseer D, Traxler M, Schoufour JD et al. (2023) "Nutritional and exercise interventions in individuals with sarcopenic obesity around retirement age: a systematic review and meta-analysis." Nutr Rev, 2023 Aug | PMID: 36882046

• Focuses on the dual burden of sarcopenia + obesity in older adults - a growing concern in physiotherapy.
• Exercise + nutrition combined was superior to either alone for preserving muscle and losing fat.

Shahid A, Thirumaran AJ, Christensen R et al. (2025) "Comparison of weight loss interventions in overweight and obese adults with knee osteoarthritis: A systematic review and network meta-analysis." Osteoarthritis Cartilage, 2025 Apr | PMID: 39233046

• Directly compares diet, exercise, and combined weight-loss strategies in obese patients with knee OA.
• Key physiotherapy-relevant finding: combined diet + exercise produced best pain and function outcomes.

O'Connor EA, Evans CV, Henninger M et al. (2024) "Interventions for Weight Management in Children and Adolescents: Updated Evidence Report for the US Preventive Services Task Force." JAMA, 2024 Jul | PMID: 38888913

• Comprehensive review supporting intensive multicomponent behavioural interventions (including physical activity) as the standard of care for childhood obesity.

Metzendorf MI, Wieland LS, Richter B et al. (2024) "Mobile health (m-health) smartphone interventions for adolescents and adults with overweight or obesity." Cochrane Database Syst Rev, 2024 Feb | PMID: 38375882

• A Cochrane review on the growing role of smartphone apps and digital tools in supporting exercise and diet adherence in obese patients.
• Relevant for physiotherapists incorporating technology into rehabilitation.

Migueles JH, Cadenas-Sanchez C, Lubans DR et al. (2023) "Effects of an Exercise Program on Cardiometabolic and Mental Health in Children With Overweight or Obesity." JAMA Netw Open, 2023 Jul | PMID: 37498603

• RCT showing structured exercise programs improved both cardiometabolic markers AND mental health in overweight children - highlighting the holistic benefit of physiotherapy-led exercise.

Li M, Li J, Xu Y et al. (2024) "Effect of 5:2 Regimens: Energy-Restricted Diet or Low-Volume HIIT + Resistance Exercise on Glycemic Control in Adults with Overweight/Obesity and T2DM." Diabetes Care, 2024 Jun | PMID: 38638032

• 3-arm RCT comparing intermittent diet restriction vs. HIIT + resistance training in diabetic obese adults.
• HIIT + resistance was effective and time-efficient - practical for physiotherapy planning.

Key Takeaways for MPT Practice

Pathophysiology of Obesity - Simply Explained

1. The Basic Idea: A Broken Scale

• Left side = Energy IN (food you eat)
• Right side = Energy OUT (what your body burns)

Fuster & Hurst's The Heart, 15th Ed. - Genes, environment, biology and behaviour all interact to tilt the energy balance scale.

2. What Controls How Much You Eat? (The Brain Connection)

🟡 Ghrelin - "The Hunger Hormone"

• Made in your stomach
• Rises when your stomach is empty - makes you feel hungry
• Goes to the brain and says: "Eat! I need food!"
• In obesity, ghrelin can stay high or become overactive, pushing you to eat more

🟢 Leptin - "The Fullness Hormone"

• Made by your fat cells
• Tells the brain: "We have enough fat stored, stop eating"
• More fat = more leptin released

The Leptin Problem in Obesity

Think of it like this: your brain's "doorbell" for leptin stops working. Leptin is ringing the bell constantly, but the brain cannot hear it. So the brain keeps thinking the body is starving and keeps sending hunger signals.

3. The Fat Cell (Adipose Tissue) Problem

When fat tissue becomes overloaded:

4. The Stress Response Inside Cells (Why Organs Start Failing)

1. ER Stress (Endoplasmic Reticulum Stress) - The cell's internal "factory" for making proteins gets overloaded and starts making mistakes. This triggers inflammation.
2. Oxidative Stress - Excess fat and sugar create harmful molecules called free radicals that damage cell walls, DNA, and proteins - like rust damaging metal.
3. Chronic Inflammation - The body's immune system, trying to deal with all this damage, stays permanently "switched on" in a low-grade way. This damages blood vessels, the pancreas, liver, kidneys, and joints over time.

5. Why Losing Weight is So Hard: The Body Fights Back

"Obesity perpetuates obesity." - Fuster & Hurst's The Heart, 15th Ed.

6. Genetics: The Background Setting

• Some people are genetically set up to gain weight more easily in the same environment as someone who does not
• More than 100 susceptibility genes for obesity have been identified
• Twin studies show that if you overfeed two identical twins by the same amount, they gain almost the same weight - proving the genetic control of body weight

7. How Obesity Causes Disease - The Chain Reaction

Excess Fat
     ↓
Adipose tissue overflow
     ↓
Inflammation + Fatty acids in blood
     ↓
┌─────────────────────────────────────┐
│  Liver: Fat accumulation → Fatty    │
│  liver → Cirrhosis                  │
│                                     │
│  Pancreas: Beta-cell failure →      │
│  Type 2 Diabetes                    │
│                                     │
│  Heart & Vessels: Atherosclerosis   │
│  → CAD, Heart Attack, Stroke        │
│                                     │
│  Joints: Extra load + Inflammation  │
│  → Osteoarthritis                   │
│                                     │
│  Lungs: Fat compresses airways      │
│  → Sleep Apnea, Hypoventilation     │
│                                     │
│  Hormones: Disrupted sex hormones   │
│  → PCOS, infertility                │
└─────────────────────────────────────┘

8. Simple Summary (Memory Aid)