Obesity and Weight Management Notes

Obesity and Weight Management

Normal Body Weight

  • Normal body weight is appropriate for maintaining good health at a particular time for an individual.
  • A healthy weight involves nutritious eating, exercise, absence of health issues, and freedom from disease.

Obesity Definition

  • Obesity is defined as abnormal or excessive fat accumulation posing a health risk.
  • Quantitatively, it is defined as:
    • Weight 20% above average.
    • BMI > 30

Weight Classifications

  • Obesity: Weight 20% above average.
  • Overweight: Weight 10-20% above average.
  • Underweight: Weight 10-15% below average.

Body Mass Index (BMI)

  • BMI is a population measure of obesity.
  • Formula: BMI=Body weight (Kg)Height2 (m)BMI = \frac{Body\ weight\ (Kg)}{Height^2\ (m)}
  • A BMI of 30 or more is generally considered obese, according to WHO and NIH.

Health Risks of Obesity

  • Strain on heart, lungs, muscles, bones, and joints.
  • Increased susceptibility to type 2 diabetes mellitus, cardiovascular diseases, and hypertension.
  • Increased surgical risks.
  • Shortened life span.
  • Psychosocial problems.
  • Association with some forms of cancer.

BMI Classes and Health Risk

  • BMI is used to determine health risk from excess weight.
  • Risk Classes:
    • Class I: Low risk
    • Class II: Moderate risk
    • Class III: High risk (morbid obesity)

Overweight and Underweight Risks

  • Overweight isn't a risk unless accompanied by conditions like diabetes or dyslipidemia.
  • Underweight health risks include:
    • Malnutrition
    • Anemia
    • Osteoporosis
    • Amenorrhea (absence of menstruation)
    • Pregnancy complications

BMI Calculation Example

  • Man weighing 90 kg, 185 cm tall:
    • BMI=90(1.85)2=26.5BMI = \frac{90}{(1.85)^2} = 26.5
    • Class: Overweight
    • Risk: No increased risk unless other conditions are present

Fat Distribution

  • Fat distribution indicates potential health problems.
  • Abdominal cavity fat (visceral fat) is associated with higher risk of hypertension, coronary heart disease, type 2 diabetes, and certain cancers compared to fat in thighs, buttocks, and hips.
  • Pear-shaped bodies have lower disease risk than apple-shaped bodies.
  • Visceral fat is stored around internal organs and is characteristic of apple-shaped distribution, associated with CVD, T2DM, and metabolic disorders.

Waist-to-Hip Ratio

  • Waist-to-hip ratio indicates risk.
  • Formula: Waist-to-hip ratio = waist circumference / hip circumference
  • Risk indicated if:
    • > 1.0 (women)
    • > 0.8 (men)
  • Increased metabolic complication risk:
    • Waist circumference > 40 inches (men)
    • Waist circumference > 35 inches (women), according to American Heart Association.
  • Fat distribution:
    • Males: Apple shape (android)
    • Females: Pear shape (gynoid)

Body Fat Composition

  • Total body fat is composed of essential and storage body fat.
  • Essential body fat:
    • Necessary for life and reproductive functions.
    • Cushions organs, provides insulation, associated with nerves and bone marrow.
    • Percentage: 2-5% in men, 10-13% in women (higher due to childbearing and hormonal functions).
  • Storage body fat: Stored in adipose tissue as a fat depot.

Normal Body Composition

  • Normal percentages of major body components (water, muscles, fat, and bones) from total body weight vary between males and females.

Histological and Physiological Features of Adipose Tissue

  • Adipose tissue is a loose connective tissue mainly composed of adipocytes.
  • Main role: stores energy as lipids, cushions, and insulates the body.
  • Types:
    • White adipose tissue (WAT): stores energy
    • Brown adipose tissue (BAT): generates body heat
  • BAT produces heat to maintain body temperature in cold conditions. It contains more mitochondria than WAT, burning calories to produce heat.
  • High BAT quantities are associated with lower body weight.
  • Newborns have considerable BAT, which decreases with age, leading to increased body weight.
  • WAT and BAT have antagonistic functions: WAT stores excess energy as triglycerides, while BAT dissipates energy through heat production.

Adipose Tissue Hormones

  • Adipose tissue is recognized as an endocrine organ, secreting hormones and inflammatory markers, affecting body metabolism, weight, energy regulation, appetite, insulin sensitivity, inflammation, atherosclerosis, and cell proliferation.

Key Adipose Tissue Hormones

  • Leptin: Satiety hormone, inhibits hunger, regulates energy balance.
  • Ghrelin: Hunger hormone, produced in the small intestine, induces appetite.
  • Leptin and ghrelin have antagonistic effects.
  • Adiponectin: Adipo-cytokine, produced by adipose tissues, has antidiabetic, anti-inflammatory, antiatherogenic, and cardioprotective effects.
  • Resistin: Secreted by adipocytes, linked to atherosclerosis, CVD, non-alcoholic fatty liver disease, rheumatic disease, malignancy, asthma, inflammatory bowel disease, and chronic kidney disease.

Causes of Obesity

  • No single cause; poor diet and inactivity are leading factors.
  • Genetic, physiological, metabolic, biochemical, and psychological factors also contribute.
  • Energy imbalance (eating more than needed).
  • Reduced activity and slowed metabolism with age.
  • Hypothyroidism (rare): Low basal metabolic rate (BMR), reducing calorie needs; can result in excess weight if uncorrected.

Hormones Involved in Body Weight Control

  • Insulin: Lipogenic.
  • Thyroxine: Thyroid hormones increase BMR; Hypothyroidism (weight gain), hyperthyroidism (weight loss).
  • Glucocorticosteroids: Weight gain due to increased visceral fat deposition and appetite stimulation
  • Intestinal hormones: Ghrelin and cholecystokinin (CCK).
  • Adipose tissue hormones: Leptin, adiponectin, resistin.

Weight Loss Theories

  • Two popular theories: fat cell theory and set-point theory.
Set Point Theory
  • Set point: Weight range in which the body is programmed to function optimally.
  • Body maintains a natural weight at which it's comfortable.
  • Weight regulated at a pre-determined level by a feedback control mechanism.
  • Explains why some can't lose weight below or quickly regain to a set point.
  • Lowering set point: through exercising three to five times a week.
Fat Cell Theory
  • Obesity develops when fat cell size increases. When size decreases, the individual is driven to eat.
  • Each body is programmed to have a basic set number of fat cells.
  • Creating new fat cells is easier than losing old ones.
  • Fat cells (adipocytes) may increase in size (hypertrophy) or number (hyperplasia).
    • Hyperplasia: increase in cell number.
    • Hypertrophy: increase in cell size.

Weight Loss Challenges

  • Each theory explains weight loss challenges and body's tendency to gain rather than lose weight.

Surgical Treatment of Obesity (Bariatric Surgery)

  • Indicated when obesity becomes morbid (BMI > 40) and diet/exercise don't work.
  • Most surgeries are minimally invasive (laparoscopic).
  • Common procedures: gastric bypass and stomach banding.
  • Other procedures: sleeve gastrectomy, adjustable gastric band, and biliopancreatic diversion with duodenal switch.

Complications of Bariatric Surgery

  • Bleeding, infections, gastritis, gallstones, and iron, vitamin B12, and calcium deficiencies.
  • Dumping syndrome: nausea, vomiting, diarrhea, bloating, and dizziness.
  • Dumping occurs when foods quickly pass into the intestines without nutrient absorption.
  • Dumping syndrome is a main complication of gastric banding and bypass, leading to late hypoglycemia due to:
    • Rapid gastric emptying → rapid glucose absorption → over-insulin secretion → hypoglycemia.

Types of Bariatric Surgery

  • Gastric Bypass: Creates a small stomach pouch and outlet directly to the small intestine, bypassing most of the stomach, the entire duodenum, and some of the jejunum.
    • Advantages: No foreign object, more durable, reliable, and effective.
  • Stomach Banding: Uses a gastric band to create a small stomach pouch; opening size can be adjusted.
    • Advantages: No malabsorption, more flexible, less invasive, safer.

Pharmacological Treatment of Obesity

  • Based on three mechanisms:
    • Reducing appetite (anorectic agents).
    • Reducing fat absorption.
    • Increasing energy expenditure.
  • Medications: CNS-acting and non-CNS acting agents.
  • Approved for patients with BMI of 30 or higher (obese) or overweight patients (BMI of 27 or higher) with significant risk factors or disease.
  • Pharmacotherapy augments, but doesn't replace, diet, physical activity, and behavior therapy.
  • Anti-obesity drugs aren't magic pills and may have side effects; monitoring is necessary.
  • Weight loss: ~2-20 kg during the first 6 months of treatment.

Three Pillars of Weight Management

Behavior Modification
  • Adhering to:
    • Active lifestyle
    • Avoid processed, high-fat, salty foods, empty calories
    • Healthy cooking methods (grilling, boiling, avoid frying)
    • Eat slowly
    • Take small portions
    • Eat fresh, whole, high-nutrient-density foods
    • Don't wait long between meals
    • Don't punish yourself if you break the diet
    • If you binge, don't punish yourself by continuing to binge
    • Join support groups
    • Avoid negative people
    • Don't be obsessed with body image
    • Be thankful for being healthy even if not slim!
Healthy Diet
  • Balanced diet:
    • Provides all nutrients in adequate amounts
    • Avoids nutritionally poor foods (high-calorie, high-fat, saturated fat, trans-fat, high-salt, processed, junk foods)
    • Includes functional foods that promote health (rich in antioxidants, dietary fibers).
Exercise
  • Health benefits: Increasing energy expenditure, maintaining healthy weight, body shaping, improving physical and biochemical fitness, increasing insulin sensitivity, increasing BMR.
  • Emphasize AEROBIC exercise (moderate intensity, long duration).
  • Daily basis:
    • 30 min: reduce risk of coronary heart disease (CHD).
    • 60-90 min: prevent weight gain.
    • > 90 min: maintain weight loss.
  • 1 kg of body fat is equivalent to 7700 Kcal.

Fad Diets

  • Aim at rapid weight loss through unhealthy and unbalanced diets.
  • Examples:
    • High protein – low CHO diet (Atkin’s diet).
    • Fluid – based diets.
    • Blood-type diet.
    • Cabbage, grapefruit… diets.
    • Crash diets (very low caloric diets).
  • Crash diets typically result in initial rapid weight loss (water and lean muscle mass rather than body fat).
  • Followed by a plateau period.
  • Can result in regaining the weight that was lost and sometimes more (yo-yo effect).
  • Severely limit foods allowed, causing nutrient deficiencies.
  • Excess of cholesterol and fat, contributing to atherosclerosis.
  • Excess protein puts too great a demand on the kidneys.
  • Rapid weight loss can cause the formation of gallstones.
  • Fail because they don't change eating habits.

Eating Disorders

  • May include inadequate or excessive food intake which can ultimately damage an individual's well-being.
  • Include Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder.
  • Combination of biological, psychological, and/or environmental abnormalities may contribute.
  • Body dysmorphic disorder (BDD) may lead to food avoidance: obsessive idea that some aspect of one's own body part or appearance is severely flawed.
Anorexia Nervosa
  • Characterized by low weight, fear of gaining weight, strong desire to be thin, and distorted body image leading to food restriction.
Bulimia Nervosa
  • Characterized by binge eating followed by purging (Binge & Purge cycles).
  • Binge eating: eating a large amount of food in a short amount of time.
  • Purging: attempts to get rid of the food consumed (vomiting or taking laxatives).
Binge Eating Disorder
  • Individuals frequently lose control over his or her eating.
  • Episodes are not followed by compensatory behaviors (purging, fasting, or excessive exercise).
  • Many may be obese and at increased risk of cardiovascular disease.
  • May experience feelings of guilt, distress, and embarrassment.

Metabolic Syndrome

  • Cluster of conditions synergistically increasing the risk of cardiovascular disease, type 2 diabetes, and premature mortality.
  • Main metabolic disorders:
    1. Abdominal obesity
    2. Impaired glucose metabolism (hyperglycemia / glucose intolerance)
    3. Dyslipidemia (usually ↑TG, ↑LDL-C, ↓HDL).
    4. Hypertension.
  • Other conditions: hyperuricemia.
  • Patient has MS if 3 of the 4 disorders are found.
  • About 35% of US population has MS (2012).
  • Main etio-pathophysiological factor is “insulin resistance”.

Therapeutic Interventions for Metabolic Syndrome

  • Preventable and treatable.
  • Lifestyle change is most important and efficacious.
  • Rate of progression can be reduced by 60% with lifestyle changes.
  • Therapy combines interventions for T2DM, dyslipidemia, hypertension, and obesity.
Lifestyle Changes
  • Diet
    1. Reduce body weight.
    2. Eat low-glycemic index and glycemic load foods.
    3. Have high-fiber diet.
    4. Avoid processed foods.
  • Exercise
    • Reduces risk by increasing insulin sensitivity, reducing blood lipids, stimulating secretion of leptin and adiponectin, reducing body weight, increasing BMR.
    • Recommended: 30 minutes or more of moderate physical activity on most days.
Pharmacological Therapy
  • Drugs to control blood glucose, lipids, and pressure; Metformin is typical.
Continuous Monitoring
  • Monitor blood glucose, lipids, pressure and parameters such as uric acid.