Nutrition Lecture 6

Obesity and Eating Disorders

• Obesity prevalence among U.S. adults (ages 20-74) increased significantly, doubling from 14.5% (1976-1980) to 35.7% (2009-2010).
• This increase affected all demographics (men, women, age groups, racial/ethnic backgrounds, and socioeconomic statuses).
• Severe obesity (BMI ≥ 40) is rising faster than other obesity classifications.
• Disordered eating involves abnormal eating behaviors impacting physical and mental health (e.g., anorexia nervosa, bulimia nervosa).
• Historically, obesity and eating disorders were studied separately, with obesity viewed medically and eating disorders psychologically/psychiatrically.
• Shared factors between obesity and eating disorders include appetite regulation, body image concerns, and overlapping risk factors.
• Treatment approaches commonly include nutrition therapy, behavior modification, physical activity, medication, and surgical interventions.

Causes of Obesity

• Energy Imbalance: Obesity results from consistently consuming more calories than the body expends, leading to fat accumulation.
• Complex Causes: Obesity is a metabolic disease influenced by multiple factors, not solely a lack of willpower.
• Individual Susceptibility: Genetic and environmental factors influence individual weight gain susceptibility.
• Set-Point Theory: The body naturally regulates its weight around a "set-point" range, affected by biological mechanisms like metabolism and hunger signals.
• Set-point resistance to change makes sustained weight loss difficult and reducing intake may trigger metabolism slowing.
• Contributing Factors: An interplay of obesogenic environments, unhealthy behaviors, and genetic predispositions contribute to weight gain.

Obesogenic Environment

• An obesogenic environment promotes high calorie intake and discourages physical activity.
• Factors that promote obesity:
  • Abundant, affordable, high-calorie foods
  • Increased consumption of soft drinks and snacks
  • Increased dining out frequency
  • Larger portion sizes in restaurants
  • Reduction in physical activity due to labor-saving devices
  • Reduced physical activity from sedentary lifestyles (TV, video games, computers).

Genetics and Obesity

• Genetic Susceptibility: Genetics significantly influence how the body responds to calorie intake changes.
• Influences:
  • Basal Metabolic Rate (BMR) – the number of calories burned at rest
  • Body Fat Distribution – where fat is stored
  • Response to overeating – some more prone to weight gain
• Individual Variability: People respond differently to calorie restriction and weight loss efforts due to genetic differences.
• Evidence for Genetic Basis: Adoption studies and BMI heritability (40%-70%) support a genetic component.

Complications of Obesity

• Obesity is linked to a higher risk of death and various chronic conditions:
  • Metabolic Disorders: Diabetes, high cholesterol (hyperlipidemia), fatty liver disease.
  • Respiratory Disorders: Obstructive sleep apnea, gastroesophageal reflux disease (GERD).
  • Musculoskeletal Problems: Vertebral disc disease, osteoarthritis.
  • Cancer: Increased risk of some cancers due to chronic inflammation and hormone changes
• Abdominal Obesity: Excess fat around the abdomen increases risk of metabolic syndrome, heart disease, and type 2 diabetes.
• Surgical and Pregnancy Risks: Obesity increases surgical and pregnancy complications.
• Psychological and Social Impacts: Obesity can lead to low self-esteem, negative body image, depression and social consequences like stereotyping, discrimination, stigma, isolation.

Goals and Challenges in Obesity Treatment

• Ideal Treatment Goals:
  • Short-term: 1-2 pounds weight loss per week (calorie deficit)
  • Long-term: Achieve and maintain a healthy BMI
• Challenges of Lifestyle Modification: Sustained weight loss requires long-term diet and activity changes, often resulting in weight regain even with initial success.
• Benefits of Modest Weight Loss: A 5-10% body weight reduction significantly improves: Blood pressure, cholesterol levels, blood sugar levels, and type 2 diabetes risk.
• Realistic Goals: Preventing further weight gain may be a more accessible goal than weight loss for some individuals. Active intervention, even without weight loss, can be beneficial.

Evaluating Motivation for Weight Loss

• Importance of Motivation: Motivation drives successful weight loss efforts.
• Risks of Imposing Treatment: Starting treatment without proper individual motivation may lead to resistance and failure.
• Assessing Motivation: Evaluate readiness for change and tailor treatment accordingly.
• Stages of Motivation (Behavioral Change Model): Precontemplation, contemplation, preparation, action, maintenance, relapse/termination.

Weight Management with Nutrition

• Comprehensive Lifestyle Approach: Includes nutrition therapy, physical activity, behavior modification, pharmacotherapy, and surgery (for high BMI/serious conditions).

Nutrition Therapy

• Calorie Reduction Strategy: Reduce daily intake by 500-1000 calories for 1-2 pounds weight loss per week. (1 pound fat = 3500 calories)
• Challenges of Sustained Weight Loss: The body adapts by lowering calorie expenditure requiring ongoing adjustments in calorie intake.

Calorie Intake Recommendations

• Women: 1000-1200 kcal/day
• Men & Active/Heavier Women: 1200-1600 kcal/day

Diet Plans for Weight Loss

• Very-Low-Calorie Diets (VLCDs): ~800kcal/day, rapid weight loss but may cause nutrient deficiencies and muscle loss; pre-surgical use is possible.
• Low-Carbohydrate Diets (Atkins-Type): Deplete glycogen stores, induce ketosis, and suppress appetite. Carb intake is typically reduced.