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Energy Expenditure, Energy Balance, Body Composition

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Food Composition

Direct calorimetry (heat release) vs. indirect calorimetry (O2 consumed)

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Physiological fuel value - what the body gets out of food

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Bomb Calorimeter: 

  • measures energy of combustion for a particular macronutrient

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Value is adjusted lower than that measured by "the bomb"

  • 4kcal per g of CHO

  • 4kcal per g of protein

  • 9 kcal per g fat

  • 7 kcal per g alcohol

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Energy Balance

Intake

  • sum of all energy provided by food and beverage consumed

  • derived from the oxidation of carbs, protein, fats and alcohol

Output

  • absorption

  • metabolism

  • storage

  • physiological process 

    • breathing​

    • heating

    • heart beats

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Intake > Output = weight gain

Components of Energy Expenditure

Basal Metabolic Rate (BMR)

  • metabolic rate at rest following sleep (no food and thermoneutral environment)

Resting Metabolic Rate (RMR)

  • ​at rest in comfortable environment, not fed, but not fasted (not digested)

  • usually approx 10% higher than BMR

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Differs from Total Daily Energy Expenditure

  • TDEE = BMR + TEF + NEAT + TEA

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Thermic Effect of Food (TEF)

  • heat created by food digestion

    • protein has highest TEF (20-30%)​

    • CHO (5-10%)

    • Fat (0-5%)

Diet-induced Thermogenesis

  • the increase in energy expenditure above basal level divided by the energy content of the food ingested (a percentage)

Adaptive thermogenesis

  • restriction in diet = slower metabolic rate

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basal thermogenesis (heat)

  • a measure of the bodys energy expenditure (BMR)

  • aside from BMR, we must also consider

    • exercise induced thermogenesis (EAT)​

    • diet induced thermogenesis (DIT)

    • non-exercise activity thermogenesis (NEAT)

    • adaptive thermogensis

study question:

  • what are factors that affect basal metabolic rate?

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study question:

  • what are the pros and cons of each of these?

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Food Intake and Satiety

  • lower-fat foods can be eaten in bigger portions for the same number of kcals

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  • other factors that determine satiety

    • genetics​

    • gender

    • age

    • nutrition satus

    • GI satiety signals

    • gut enzymes

    • gastric emptying rate

    • gut microbiota

    • sleep

    • behavioral response to food

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  • HORMONAL INFLUENCE

    • hypothalamus​

      • central control via vagus nerve​

    • anorexigenic (appetite suppressant)​

      • leptin​

      • adiponectin

    • orexigenic (appetite stimulant)

      • ghrelin​

      • neuropeptide Y

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study questions:

  • how do these hormones work? Think: 

    • what do anoexigenic/orexigenic hormones produce? what do they inhibit?​

  • what is the relationship between:

    • leptin and insulin?

    • adiponectin and insulin?

    • ghrelin and neuropeptide Y?

  • what is the difference between:

    • leptin and adiponectin?​

    • ghrelin and neuropeptide Y?

  • do obese individuals have increased or decreased circulating leptin?

Leptin

  • signals body to stop eating, stop storing fat and increase energy expenditure

  • correlation between BMI and [leptin] is 0.9

  • extra-hypothalamus functions: 

    • FA oxidation via AMPK reaction​

    • inhibits insulin secretion

    • suppression of insulin signaling in hepatic cells and both white and brown adipose tissue

Relationship between Leptin and Insulin

  • leptin decreases insulin release through a feedback loop regulated by leptin sensitive pancreatic beta cells

  • at the adipocyte, insulin unregulated GLUT-4 and LPL which leads to increased TAG synthesis

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Adiponectin

  • exhibits anti-diabetic, anti-inflammatory, and anti-atherogenic effects, and it also functions as insulin sensitizer

  • influences macronutrient metabolism via AMPK activation

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Ghrelin

  • stimulates release of neuropeptide Y to increase food intake

  • peak ghrelin concentration related to meal patterns and may rise in anticipation of eating rather than elicit feeding

  • influences AMPK --> AMPK + Pi (activated form)

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Neuropeptide Y

  • neuroendocrine factor that stimulates appetite, increases fat storage decrease EE

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Hormone Summary

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Body Weight, Body Composition, and Health

  • Body composition

    • weight alone does NOT determine health​

  • Body weight

    • BMI - indication of adiposity​, does not actually determine body fat %

    • high BMI does not always equal high fat %​

      • example: Arnold Schwarzenegger had a BMI of 33.4!

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study questions:

  • what are some reasons BMI is not a good indicator of adiposity and bad health?

  • which is a better indicator of health: body composition or body weight? Why?

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Body Fat and Distribution

  • some people need less body fat

    • overweight and obese individuals​

    • individuals at high risk for CVD, cancer and T2DM

  • some people need more body fat

    • menstruating women​

    • underweight individuals

  • fat distribution

    • intra-abdominal fat (visceral)​

    • central obesity (subcutaneous)

    • android (apple) vs gynoid (pear)

study question:

  • excess of which type of fat distribution is worse for overall health?

  • increased health risk: 

    • BMI of ≥25​

    • BMI of ≤17.9

    • waist circumference of

      • men: >40in​

      • women: >35in

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©2023 by Syracuse University Dr.Margaret Voss

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