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Regulation of Energy Balance and Body Weight

Regulation of Energy Balance and Body Weight. Problem 1 Obesity Unit I Year 2. Learning objectives. To understand the concept of energy balance Define metabolic rate and basal metabolic rate List factors affecting basal metabolic rate

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Regulation of Energy Balance and Body Weight

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  1. Regulation of Energy Balance and Body Weight Problem 1 Obesity Unit I Year 2

  2. Learning objectives • To understand the concept of energy balance • Define metabolic rate and basal metabolic rate • List factors affecting basal metabolic rate • To describe the neuronal and hormonal control of food intake • To list hormones and neurotransmitters increasing food intake (orexigenic) and (anorexigenic) substances that inhibit feeding

  3. Energy Balance Stable body weight whenever input and expenditure are balanced

  4. SDA

  5. Obesity • Occurs when there is greater energy intake than energy expenditure

  6. Daily Energy expenditure Body Energy = In –Out Energy input (per gram) Carbohydrates  4 kcal Fat  9 kcal Protein  4 kcal 25% 8-10% 60-65%

  7. Measurement of energy production • Direct calorimetry • Indirect calorimetry : by measurement of oxygen consumption of the body per unit time ( metabolic rate) • Metabolic rate is energy expenditure per unit time and is measured in kcal of heat produced per hour

  8. What is Basal Metabolic Rate (BMR) ? • The metabolic rate determined in a subject at rest in a room at a comfortable temperature in the thermoneutral zone 12 to 14 h after the last meal is called the basal metabolic rate (BMR). • The BMR of a man of average size is about 2000 kcal/d.

  9. FACTORS AFFECTING THE METABOLIC RATE • Height, weight, and surface area • Sex • Age • Muscular exertion • Recent ingestion of food • High or low environmental temperature • Growth • Reproduction • Lactation • Emotional state • Body temperature • Circulating levels of thyroid hormones • Circulating epinephrine and norepinephrine levels

  10. What is obesity? • Abnormal or excessive fat accumulation in the body to the extent that health may be impaired • If energy in > energy out, excess is stored as fat (9.3 kcal of excess  about 1 gram of fat stored) • If energy in < energy out , wight loss occurs

  11. How is food intake (energy balance) regulated? • Neuronal regulation: neural centers in the hypothalamus • Endocrine regulation (hormones) • Levels of metabolites in the plasma (glucose , amino acids and fatty acids) • Hormones and metabolites acts on the hypothalamus to regulate food intake .

  12. Hypothalamic centers controlling food intake Hunger center: Stimulation: hyperphagia Destruction: Lack of desire to eat (emaciation) Emaciation: weight loss Satiety center : Stimulation suppress feeding, aphagia Destruction: over eating , obesity

  13. ARCUATE NUCLEUS Pro-opiomelano cortin (POMC), (CART) pathway release melanocortin: decreases food intake Agouti-related protein (AGRP) , NPY pathway : increases food intake Control of enrgy balance by the hypothalamus

  14. Control of angry balance by two neuronal pathways in the hypothalamus

  15. The factors that regulate appetite through effects on central neural circuits

  16. Decrease Feeding (Anorexigenic) • α-Melanocyte-stimulating hormone (α-MSH) • Cocaine-amphetamine-regulated transcript (CART • Leptin • Serotonin • Norepinephrine • Corticotropin-releasing hormone • Insulin • Cholecystokinin (CCK) • )) • Glucagon-like peptide (GLP • Cocaine- and amphetamine-regulated transcript (CART) • Peptide YY (PYY)

  17. Increase Feeding (Orexigenic) • Neuropeptide Y (NPY) • Agouti-related protein (AGRP) • Orexins A and B • Endorphins • Galanin (GAL) • Amino acids (glutamate and γ-aminobutyric acid) • CTR • Ghrelin • Endocannabinoids

  18. Adipocytes peptides related to obsity Adiponectin, an abundant adipose-derived protein whose levels are reduced in obesity, enhances insulin sensitivity and lipid oxidation and it has vascular-protective effects, whereas resistin whose levels are increased in obesity, may induce insulin resistance. These factors, play a role in the physiology of lipid homeostasis, insulin sensitivity, blood pressure control, coagulation, and vascular health and are likely to contribute to obesity-related pathologies

  19. Concept of a body weight "set point” • When fat stores are less, the adipostat signal is low, and the hypothalamus responds by stimulating hunger and decreasing energy expenditure to conserve energy. • When fat stores are too much , the signal is increased, and the hypothalamus responds by decreasing hunger and increasing energy expenditure. • This is by obesity (ob) gene, and its product leptin, and the dibates (db) gene, whose product is the leptin receptor,

  20. The endocannabinoid system (ECS) • is a group of endogenous cannabinoid receptors located in the mammalian brain and throughout the central and peripheral nervous systems, consisting of neuromodulatory lipids and their receptors. Known as "the body’s own cannabinoid system. • The ECS is involved in a variety of physiological processes including appetite, pain-sensation, mood, and memory, and in mediating the psychoactive effects of cannabis

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