Question What determines whether the energy in the foods you eat is used to fuel your body or stored for later use? Amount of energy in the body Hormones: insulin, glucagon, etc Environments: fight/flight, emotions Hypothalamus: hunger center of the brain

Energy Balance ~ go over handout ~

Energy Balance Energy intake & energy expenditure Energy store = energy intake – energy expenditure Negative energy balance Results in weight loss, but not necessarily losing fat… Positive energy balance When is this favorable? How does the body respond to each of the above? Positive energy balance = taking in more; Negative energy balance = taking in less A change in body weight is a useful INDICATOR of whether your are in positive or negative energy balance

Types of Adipose Tissues Something you already know: Adipocytes make up adipose tissues Visceral adipose tissue (VAT) protect & support body organs Subcutaneous adipose tissue (SCAT) Insulation – body temperature

http://webdocs.cs.ualberta.ca/~dana/Research/muscle/res.jpg http://ars.els-cdn.com/content/image/1-s2.0-S009829971200115X-gr1.sml

Functions of Adipose Tissues More functions: Vitamin A, D, E, K absorption Cell membrane Transportation (lipoprotein) Communication (PPAR) – Adipokines Adipose tissues are considered as one of the largest endocrine organ in the body

Growth of Adipose Tissue Something new: Hypertrophic growth Hyperplastic growth Adipose tissues is the source of several hormones, it plays an active role in regulating energy balance. The discovery that adipocytes are a source of hormones and hormone-like substances collectively called adipokines, had led many researchers to consider adipose tissue to be the largest endocrine organ in the body.

Question What makes you eat? Why you make certain food choices? Hunger, mood, social norm, boredom, etc. Taste, health, religion, cultural, env, peer pressure, etc. Many facets of your life Numerous purposes beyond providing energy Psychological, physical, social, and cultural forces

Physiological Influence on Energy Intake Hunger & Satiety

Hypothalamus Communications between body organs sending and receiving signals Releases neuropeptides (brain proteins) catabolic & anabolic Factors influencing hunger and satiety Gastric stretching (digestive sys) Circulating nutrient level (circulatory sys) GI hormones (endocrine sys) CNS

Gastric Stretching Mechanorecepters  neurotransmitters  brain Size of stomach High-volume food: liquid & fiber Bariatric surgery Surgeries involved in losing weight Gastric banding Gastric bypass

Bariatric Surgery Bariatric Surgery pg 348 http://oreillyvisualization.com/2011/08/gastric-banding/ http://www.hurtbyadoctor.com/images/Gastric-Bypass-Malpractice_001.jpg Bariatric Surgery pg 348

Blood Nutrient Concentration Chemoreceptors  neurotransmitters  brain Glucose The brain is sensitive to blood glucose level Amino acids stimulate the release catabolic neurotransmitters Tryptophan is used to synthesize serotonin Lipids weaker affect because easily overcome by tasty flavor Tryptophan-rich foods make you happy and sleepy

GI Hormones Decrease intake: CCK Decrease intake: PYY small intestine protein and fatty acids (so the pancreas releases pancreatic enzymes) Decrease intake: PYY small & large intestine food Increase intake: ghrelin Stomach Prior to a meal There are other GI hormones, but you need to know only the three mentioned above.

Psychological Influence on Energy Intake Appetite

Food Aversion & Food Craving Sensory factors: taste, smell, appearance, etc. Emotional states: fear, depression, disappointment, excitement, stress, etc Strong psychological factors  eating disorders

+ and – energy balance physiological psychological TEE VAT & SCAT Adipokines (PPAR) Hyperplastic & hypertrophic growth physiological Hunger & satiety Gastric stretching (bariatric surgeries) Nutrients in the blood (tryptophan  serotonin) Gi hormones (CCK, PYY, ghrelin, insulin, glucagon) Hypothalamus (neuropeptides) psychological Food aversion and craving (appetite) Social aspects in eating TEE

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Total Energy Expenditure

Total Energy Expenditure (TEE) Basal metabolism Physical activity Thermic effect of food Adaptive thermogenesis Nonexercise activity thermogenesis relatively small

Basal Metabolism Accounts for most of TEE (50-70%) Sustain basic, involuntary life functions BMR = kcal/hour & BEE = kcal/day not including food processing & physcial activity Stringent conditions RMR = kcal/hour & REE = kcal/day Usually 10% higher than BMR/BEE

Harris-Benedict Equation Estimating REE Male 66.5 + [13.8 x weight (kg)] + [5 x height (cm)] + [6.8 x age] Female 655.1 + [9.6 x weight (kg)] + [1.8 x height (cm)] + [4.7 x age] Note that this is just an estimation and may not apply to every individual. Why not?

Factors Affecting BMR Age Sex Growth Body weight Body shape Body composition Body temperature Stress Pregnancy Lactation Energy/Food restriction

Physical Activity Accounts for 15-30% of TEE Amount of physical activity: sedentary vs. active Type of physical activity Body size

Thermic Effect of Food (TEF) Account for the least amount of TEE (5-10%) Food process - energy used to digest, absorb, transport, metabolize, and store nutrients Influenced by the amount and type of food we eat protein foods have high TEF fatty foods have low TEF

Measuring TEE Accurate measurements require expensive equipments and high degree of expertise Direct calorimetry – measures body heat ~60% of energy/glucose is released as body heat Indirect calorimetry – measures O2 intake and CO2 output 1L of O2 is used to metabolize 4.8kcal of nutrients IOM developed EER as part of DRI