BMR and Obesity 2020 Imam Abdulrahman Bin Faisal University PDF

Basal Metabolic Rate (BMR) and Obesity Department of Physiology College of Medicine Dr.Maiadah Alfares [email protected] Tuesday,...

Basal Metabolic Rate (BMR) and Obesity Department of Physiology College of Medicine Dr.Maiadah Alfares [email protected] Tuesday, September 1, 2020 Objectives What is BMR and the factors affecting BMR? The concept of energy balance Regulation of food intake What is obesity? And its classification Exercise Energy Balance First law of thermodynamics Energy cannot be created or destroyed Energy input-output balance Energy input : ingested food Energy output External work : Skeletal muscles are contracted to move external objects or to move body in relation to the environment Internal work : All other forms of biological energy expenditure that do not accomplish mechanical work outside the body Energy Conversion Energy from nutrients that is not used energize work >> Transformed into thermal energy or heat Only about 25% of chemical energy in foods is harnessed to do biological work , 75% is converted to heat (maintain body temperatures ) Basal Metabolic Rate (BMR) The metabolic rate is an energy expenditure/unit of time Energy expended by the body during both external and internal work. Measured in kilocalories of heat produced per hour. BMR is a metabolic activity necessary to maintain the basic body functions at rest”  The difference bet. The temp of water entering and leaving the Measurement of BMR chamber BMR Direct calorimetry Indirect Calorimetry ( O2 Uptake) Food + O2 Co2 + H2O+ energy ( mostly heat) Measurement of BMR Basal metabolic rate should measure at: Physical rest Mental rest Room No food temperature within 12 hrs Factors affecting BMR Gender Smoking Exercise Food Hormones BMR Pregnancy Sleep Age Temperature Energy Balance Energy Input Energy output Weight Weight gain loss Positive Energy Negative Energy balance balance Regulation of food intake Short-term regulation Long-term regulation Maintenance of Size and frequency of normal quantities of meal energy stores in the body Appetite control at Arcuate Nucleus of Hypothalams Melanocortin Neuropeptide Y stimulating (NPY) hormone (α – secreting neurons MSH) Secreting neurons Stimulate Decreases appetite appetite ↑ Food intake ↓ Food intake Long term maintenance of energy balance Leptin: (secreted from adipocytes) Insulin: (secreted from Serum leptin levels are directly Pancreas) proportional to body fat stores High Leptin suppresses Released in response to appetite by inhibiting NPY hyperglycemia secreting neurons and High Insulin suppresses stimulating melanocortins appetite by inhibiting NPY secreting neurons. secreting neurons and Opposite effects are produced stimulating melanocortins when leptin is low secreting neurons. Short term Regulation of eating behavior Ghrelin (secreted from Peptide YY (PYY; produced stomach) by small and large intestine) called “Hunger hormone” It is the counterpart of Ghrelin because it stimulates appetite by it inhibits appetite by inhibiting stimulating hypotalamic NPY- hypotalamic NPY- secreting secreting neurons neurons Initiates meals + Terminates meals - What is the result of positive energy balance and dysregulation of GI hormones? Obesity Is defined as excessive fat content in the adipose tissue stores. Exercise Physiology Energy for Muscle Contraction ATP is required for muscle Sources of ATP contraction Myosin ATPase Phosphocreatine (PC) breaks down ATP as Glycolysis fiber contracts Oxidative phosphorylation Energy Systems for Exercise Mole of Time to Energy Systems ATP/min Fatigue Immediate: Phosphagen 4 5 to 10 sec (Phosphocreatine and ATP) Short Term: Glycolytic 2.5 1.0 to 1.6 min (Glycogen-Lactic Acid) Long Term: Aerobic 1 Unlimited time Interaction between the energy systems & ATP Production It is a always combination of Anaerobic contribution is Aerobic contribution is anaerobic and aerobic; one greater during short term, greater during long term, just dominates: high intensity activity lower to moderate intensity Cardiovascular changes during exercise * Heart Rate * Venous Return * Stroke Volume * Cardiac output * Blood flow to skeletal muscles ,heart muscle and skin * Mean arterial blood pressure * Blood flow to GIT, Kidneys and other organs * Total Peripheral Resistance * Blood Flow to the Brain remains Unchanged Why a diabetic patient is recommended to exercise frequently? How can exercise reduce plasma hyperglycemia?  Active skeletal Resting skeletal Muscles Do not Muscles depends on depends on insulin insulin for uptake of for Uptake of glucose glucose