Hunger and Eating

Module 4: Motivation

Chapter 9: Hunger Eating Health

Chapter Overview

  • A. Digestion, Energy, Storage

  • B. Theories of Hunger and Eating

  • C. Factors That Determine What, When, and How Much We Eat

  • D. Body Weight Regulation

  • E. Obesity

Chapter Details
A. Digestion, Energy, Storage

  • Define:

    • Digestion is the process by which food is broken down into smaller components that can be absorbed into the bloodstream. This process involves both mechanical and chemical breakdown of food.

  • Steps in Breaking Down Food:

    1. Ingestion: Taking in food via the mouth.

    2. Digestion: Mechanical and enzymatic breakdown into simpler forms (e.g., proteins to amino acids).

    3. Absorption: Nutrients are absorbed through the intestines into the bloodstream.

    4. Excretion: Remaining waste is eliminated from the body.

  • Food extraction (what we extract from fats, proteins, complex carbs):

    • Fats: Extracted fatty acids and glycerol.

    • Proteins: Extracted amino acids.

    • Complex Carbohydrates: Extracted simple sugars (e.g., glucose).

  • Forms of Energy Storage:

    • Glycogen (stored in liver and muscle tissue), triglycerides (stored in adipose tissue).

  • What two factors control energy metabolism:

    1. Hormones (e.g., insulin and glucagon).

    2. Nutrient availability (availability of glucose and fatty acids).

  • Three phases of energy metabolism:

    1. Cephalic Phase:

    • Define: The initial phase of energy metabolism that occurs before food intake, activated by the sight, smell, or taste of food.

    • Insulin is high during this phase, as the body prepares for incoming energy.

    1. Absorptive Phase:

    • Define: The phase following food intake where the body absorbs and utilizes nutrients.

    • Glucagon levels low during this phase.

    • Cephalic and Absorptive phase promotes:

      • Moves energy (fats, amino acids, glucose) from blood to storage.

      • Converts glucose to glycogen and fat.

      • Converts amino acids to protein.

      • Stores glycogen in liver and muscle.

      • Fat is stored in adipose tissue.

      • Protein is stored in muscle.

    1. Fasting Phase:

    • Define: The phase during which food intake is absent and the body relies on stored energy.

    • Glucagon levels high during this phase.

    • Insulin levels low.

    • Promotes:

      • Converts stored fats to energy.

      • Converts glycogen to glucose as a primary fuel source.

B. Theories of Hunger and Eating

  • Set-Point Assumption:

    1. What is it?

    • The idea that the body has a biologically predetermined weight range that it tries to maintain, often referred to as a "set point".

    1. Three Components:

    • 1) Sensory inputs related to hunger and satiety.

    • 2) Biological mechanisms like metabolism.

    • 3) Behavioral aspects of eating.

    1. What is a negative feedback system?

    • A self-regulating process where deviations from a desired norm (set point) trigger actions that counteract such changes to return to that norm.

    1. Two Examples of Set-Point Theories:

    • Body weight regulation often involves homeostatic mechanisms of hunger and satiety.

    • Weight alterations trigger physiological responses aimed to restore the original weight.

  • Issues with Set-Point Theory:

    1. Variability in individual body weight regulation (some people maintain weight outside of the set-point).

    2. Influence of environmental factors, such as the availability of high-calorie foods.

    3. Changes in metabolism over lifetime and factors like age or health status that can alter the set-point.

  • Positive Incentive Perspective:

    • Emphasizes the role of expected pleasure from food (positive incentives) rather than just physiological regulation, accounting for societal and cultural influences on eating behavior.

C. Factors That Determine:

  • A. What We Eat:

    • Learned Preferences and Aversion:

    • People develop specific likes and dislikes for various foods based on experience and exposure.

    • Learning to Eat Vitamins and Minerals:

    • i. Design and outcome for thiamine deficient diets in rats:

      • Studies showing rats can learn to prefer foods containing essential nutrients when deprived.

    • ii. Implications for humans:

      • Highlights the importance of nutrient awareness in human dietary habits.

  • B. When We Eat:

    • Premeal Hunger:

    • The sensation of hunger that precedes meals, influencing eating time and amount.

    • Pavlovian Conditioning:

    • i. Rat Study:

      • Research demonstrating that environmental cues can trigger hunger responses in conditioned rats.

  • C. How Much We Eat:

    • Satiety Signals:

    • Three signals that indicate fullness: hormonal signals, sensory cues, and gastric responses.

    • How the following affect satiety signals:

    • 1. Appetizer Effect:

      • Initial small quantities of food can increase subsequent hunger and overall food consumption.

    • 2. Serving Size:

      • Larger portion sizes often lead to increased consumption.

    • 3. Social Influences:

      • Eating behaviors may adjust based on social contexts (e.g., eating more in groups).

    • 4. Sensory Specific Satiety:

      • The phenomenon where a person becomes satiated with specific foods while still desiring other types of food.

      • Cafeteria Diet (Experiment):

      • Studying dietary choices leads to more consumption when a variety of food is available, reflecting adaptive consequences.

D. Obesity

  • Reasons for Concern:

    • Obesity is linked to numerous health issues, including diabetes, heart disease, and overall mortality.

  • Causes of Obesity:

    1. Evolutionary Factors:

    • Human evolution has favored fat storage as a survival mechanism.

    1. Cultural Factors:

    • Societal norms and food availability influence eating behaviors and perceptions of body image.

  • Why Some but Not Others Become Obese:

    1. Consumption Patterns:

    • Differences in types, quantities, and frequencies of food consumption.

    1. Energy Expenditure:

    • a. NEAT (Non-Exercise Activity Thermogenesis):

      • Daily energy expenditure from non-exercise activities, influencing overall energy balance.

    1. Microbiome:

    • The gut microbiome composition can influence body weight and metabolic processes.

    1. Genetics:

    • Genetic predispositions affect metabolism, hunger signals, and fat storage.

  • Weight Loss Programs:

    1. Dieting Cycle:

    • Issues with yo-yo dieting and its impacts on metabolism and mental health.

    1. Physical Exercise:

    • a. NEAT:

      • Incorporating more physical activity into daily routines to enhance energy expenditure.

  • Treatments for Obesity:

    1. Gastric Bypass:

    • A surgical procedure that alters digestion to limit food intake and absorption.

    1. Gastric Band:

    • A device placed around the upper part of the stomach to restrict food intake.

    1. Gastric Sleeve:

    • A surgery that removes part of the stomach to reduce its size and capacity.

    1. GLP-1 Agonists:

    • Medications that mimic incretin hormones to promote insulin secretion and decrease appetite, aiding weight loss.