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Lecture 16

HES 250 Lecture 16: Nutrient Metabolism in Special Cases

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The College of New Jersey
Health and Exercise Sci
HES 250

Nutrient Metabolism in Special Cases (chapter 10) 5/1/17  Major factors influencing carbohydrate and fat metabolism: o Intensity o Gender o Duration o Age o Mode (type of exercise) o Metabolic diseases o Training status  Calculation of carbohydrate oxidation RQ = VCO2/VO2 ↓ ↓ caloric % usage equivalent of carbohydrate (kcal/L2 ) ↓ energy expenditure ↓ ↓ Carbohydrate oxidation = energy expenditure × % usage of carbohydrate  Does carbohydrate oxidation mean the same thing as muscle glycogen utilization? (No.) o Muscle glycogen supplies energy during muscle contraction o Liver glycogen maintains blood glucose o Carbohydrate oxidation measures the TOTAL bodily carbohydrates used  Measuring substrate utilization o Indirect calorimetry (measuring RQ  total carbohydrate oxidation) o Combining muscle biopsy with indirect calorimetry  Measuring muscle glycogen utilization  Total – muscle = liver glycogen utilization  How do these fuel utilization patterns differ between men and women? Men Women o Study: Determinants of fat oxidation during exercise in healthy men and women: a cross- section study  Women burn proportionally more fat and less carbohydrates compared to men (at same relative intensities o Study: Regulation of exercise carbohydrate metabolism by estrogen and progesterone in women.  Estrogen partially responsible for the higher fat utilization  Progesterone may have a counter-effect  Effect of estrogen on fuel utilization during exercise: o Carbohydrate metabolism: inhibits gluconeogenesis and blood glucose o Fat metabolism: stimulates adipose tissue lipolysis and intramuscular fatty acid utilization  Activates the lipase that catalyzes lipolysis  Stimulates vasodilation in muscle, thus increasing 2 supply  Hormonal responses during pregnancy o ↑ placenta  ↑ estrogen o Estrogen level stays elevated during pregnancy o Issues related to pregnancy:  Blood glucose utilization is more inhibited  reduced ability of maternal tissues to absorb blood glucose  can lead to insulin resistance  hyperglycemia  gestational diabetes (worst case, healthy women generally not at risk)  Hormone therapy with estrogen o Risk of insulin resistance o Postmenopausal women taking oral estrogen are more insulin-resistant than women not on HRT, even when women are of comparable total and abdominal fat  Exercise during pregnancy o Benefits:  Prevent de-conditioning  Maintain muscular strength and speed delivery  Reduce unnecessary weight gain  Avoid insulin resistance and potential gestational diabetes o Prescription:  Frequency: 3-4 times per week  Intensity: light to moderate  Time: 30-45 minutes  Type: use more weight bearing exercises as pregnancy advances  Avoid vigorous exercise and monitor environment condition (Elderly)  Sarcopenia – the degenerative loss of skeletal muscle mass (~1% loss per year after the age of 35) and strength associated with aging  Why is maintaining lean body mass important? o Lean body mass is more metabolically active and has higher RMR o Lean body mass has more mitochondria and capillaries which help with burning fat o Lean body mass helps regulate blood glucose level by responding to insulin and absorbing glucose from blood  Liver and muscle seen in obese and insulin resistant individuals o Both have growing fat tissue within (circulation blocked, glucose harder to absorb) o Must preserve quality of lean body mass  Skeletal Muscle and Mitochondria o Mitochondria house cellular respiration that
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