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7. Energy and Food chapter 8

7. Energy and Food chapter 8. Energy = the ability to do work. A calorie is the amount of heat (or energy) needed to raise the temperature of one gram of water by one degree Celsius. A kilocalorie (kcal) is 1000 calories. A joule is 0.24 calories.

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7. Energy and Food chapter 8

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  1. 7. Energy and Food chapter 8

  2. Energy = the ability to do work A calorie is the amount of heat (or energy) needed to raise the temperature of one gram of water by one degree Celsius. A kilocalorie (kcal) is 1000 calories. A joule is 0.24 calories. Almost all of the chemical energy contained in any substance is stored in its chemical bonds.

  3. calorie vs kilocalorie

  4. Bond Energy • The E required to break a chemical bond or • The E released when the bond is formed • C-H ~ 100 kcal/mole; C-C ~ 90kcal /mole; • O-H~ 110 kcal/mole; C=O~ 170 kcal/mole • O=O ~118 kcal/mole

  5. An exothermic reaction is a reaction that releases heat as it proceeds . CH4 + 2O2 CO2 + 2H2O + energy exo endo An endothermic reaction is a reaction that absorbs heat as it proceeds .

  6. Why is this reaction exothermic? • E required to break the bonds of reactants is 4 x C-H bond E + 2 x (O=O) bond energy = 4 (100) + (2 x118) = 636 kcal • E liberated when bonds of products are formed = 2 x (C=O) bond Energy +4 x (O-H) bond E ie (2x170) + 4 (110) = 780 kcal • Thus Energy is released in this reaction: 780-636= 144 kcal/ mole of methane burned

  7. FOOD = FUEL FOR THE HUMAN ENGINE The Energy Equation Energy In = Energy Out + Energy Stored Metabolism is the combination of all chemical reactions that take place in any living organisms. 1 Kilocalorie = 1 nutritional Calorie (Cal)

  8. ENERGY IN: The Macronutrients The macronutrients of our food are the three major groups that make up the great bulk of our food supply, the chemicals that serve as the only source of energy for the human machine .

  9. Through the elegant, intertwined complex of chemical reactions that constitute human metabolism, the chemical energy of these compounds becomes transformed into the human energy of our lives . The Macronutrients fats and oils carbohydrates protein

  10. Energy from Macronutrients • From fat: 9 Calories per gram • From protein: 4 Calories per gram • From carbohydrate: 4 Calories per gram

  11. Why do we get more calories from fat than from carbs or protein? • Fats contain long hydrocarbon chains in the fatty acid part of the molecule • More C-H bonds to be oxidized to Water and CO2. • Recall relatively high bond Energy in C=O and O-H vs. C-C and C-H bonds (methane combustion ).

  12. Calories for Healthy Eating • Recommended levels from macronutrients • From carbohydrates (55%): 10% from simple sugars (sucrose, glucose, fructose); 45% from complex carbohydrates (starch) • From fat (30%): maximum 10% from saturated fat, best from unsaturated • From Protein (15%)

  13. Some would disagree • Atkins Diet : advocated as few calories as possible from carbohydrates • Theory (1972 book) was that sugars and carbohydrates increase insulin levels and facilitate fat storage • Depriving the body of carbohydrates facilitates fat burning and hence weight loss

  14. Problems with the Atkins diet • Too much saturated fat -> coronary disease • Too little fibre, hence poor waste product elimination and risk of kidney disease and colon cancer • Conclusion: Not a healthy alternative • Expensive: Permitted foods were Atkins Diet products

  15. Atkins Diet products

  16. North American Problems • Too much simple sugar • Too much saturated fat • Too many calories!! • Not enough physical activity • Obesity is a major health issue

  17. Micronutrients • Food components such as Vitamins and Minerals, which are required in relatively small amounts for good health • Not significant sources of calories

  18. What is Junk Food? • Food that supplies a large number of calories but few Vitamins or Minerals (Micronutrients) • “Empty Calories” –ie. highly refined sugar (Sucrose) –provides calories but no micronutrients

  19. “Empty”Calories from soft drinks • Classic Coke 42 grams of sugar per 341 mL can x4 Cal/gr= 168 Calories • Diet Coke: no sugar, artificial sweeteners (aspartame and potassium acesulfame) 0 Calories (on can) • Carbonated water, caramel flavor, caffeine, phosphoric acid, citric acid, sodium benzoate, 0.1 gr of protein, so not quite 0 Cal.

  20. Enzymes in Digestion • Enzymes (bio-catalysts) help to break down complex substances into simpler ones which can be absorbed • Need optimal pH-ie pepsin in the stomach works best at pH near 2 • Suffix “ase” denotes an enzyme

  21. Carbohydrase enzymes • Amylase in saliva, breaks starch and complex carbohydrates into maltose • Maltase then breaks the maltose into glucose • Sucrase, lactase act on sucrose and lactose breaking them down into simpler sugars such as glucose and fructose

  22. Protease enzymes • Pepsins-secreted in stomach and pancreas to help proteins break down into peptides and eventually into amino acids

  23. Lipases • Secreted in pancreas and walls of the small intestine • Digest lipids (fats) and breaks them up into fatty acids and glycerol

  24. Digestion

  25. ENERGY OUT Exercise Specific Dynamic Action Basal Metabolism

  26. Specific dynamic action, SDA, the energy consumed in digesting and metabolizing food and converting its energy for use in exercise and basal metabolism. It is the price we pay, in energy, for extracting energy from food . (~10% of the energy obtained from food) ie. consume 2500Cal and use 250Cal for SDA

  27. We can sense SDA in operation as we grow warmer and find our heart beating a bit faster after a meal. The warmth and higher pulse are both signs that our body is working at digesting the food and using up energy through SDA. Drowsiness after a large meal comes from the diversion of blood from the brain to the digestive system. The body is working hard to process all the fuel that’s just been brought in and - first things first - digestion takes momentary precedence over mental alertness.

  28. After a great dinner!

  29. Basal metabolism accounts for all the work that goes on inside our bodies just to keep us alive. It is the energy expended as our heart pumps, as our lungs expand and contract, and as the liver, kidneys and other major organs work to maintain life .

  30. In a healthy adult the energy spent through Basal Metabolism amounts to approximately 1 Calorie / hour / kg of body weight Basal metabolism increases with any bodily stress, desirable (eg. pregnancy or lactation) or not (eg. illness). Measured at rest, but awake, after a 12 hour fast

  31. Calorie needs for inactive male • For 70 kg (154lb) man; need 24 x 70= 1680 Cal per day for basal metabolism • But also need additional amount for SDA which is about 10% more. Thus ~ 1900 Cal/day total

  32. Resting metabolism represents the combination of basal metabolism and SDA.

  33. Energy Availability & Storage • Instant: blood sugar (Glucose) lasts ca. 30 minutes • Short term Liver and muscles store glycogen (about 2500 Calories) max 6-8 hours. • Long term: fat is stored in adipose tissue-can last up to 35 days

  34. Hitting the Wall • Marathon runners use ~ 15Cal/minute • After 2.5 hours, use 150x 15=2250 Cal • Glycogen tank is empty!! • Need to consume short term E : glucose etc. • Fat metabolism is slow and thus of no use as a short term E source

  35. Water content of adipose tissue • Why only 7.7 Cal/gram stored in adipose tissue if fat provides 9 Cal/gram? • A: ~ 15% of adipose tissue is water • Thus : 9- (.15x9) = 9- 1.35 =7.65 Cal/gram

  36. The evolution of man • Sedentary lifestyle needs fewer calories

  37. Daily Energy Needs According to Physical Activity Activity Level Factor Very light Men Women Light Men Women Moderate Men Women Heavy Men Women To estimate your energy needs , multiply your estimated BMR (10x your weight in lbs.) by the factor listed in the table that best represents your general level of daily activity. Very Light : mostly sitting and standing activities Light : mostly walking activities Moderate : cycling, tennis, dancing Heavy : heavy manual digging, climbing, basketball, soccer 1.3 1.3 1.6 1.5 1.7 1.6 2.1 1.9

  38. Typical 175 pounder • Caloric requirement is 10x 175 x1.3 if inactive, ie 2275 Calories per day. • If you play for the Ottawa Senators, 175 x 10 x 2.1= 3675 Calories per day • Females: a bit lower ca 1900 Cal/day • Q: Do women have more efficient metabolisms? A: yes! Women have less muscle and more fat (on the average).

  39. How many soft drinks per day? • Recall max. 10% of Cal. from simple sugars, so 10% of 2275 =227.5 Cal/ • Recall one can of regular Coke contains over 160 Cal • So, the answer is…………………..1 .

  40. Calories from Alcohol • 7 Calories per gram • Thus in a 341mL can of normal beer (5 %), assuming its density is 1 gram per mL • Calories = .05 x 341 x 7 = 119.35 • A glass of wine or a shot (1.5 oz of liquor) have about the same caloric content • No nutrients, depresses CNS and is toxic to liver

  41. Recommended levels of alcohol • Max. 2 drinks per day (male adult) • Max. 1 per day (adult female) • 0 per day if pregnant or lactating! • 0 per day if on certain medications • Moderation is KEY!!

  42. Approximate Rates of Energy Expenditure for a 70kg (154lb) Person Calories Expended Level Examples Per Minute Per Hour Very light Sitting, reading, watching TV, writing, driving Light Slow walking, washing, shop- ping,light sports such as golf Moderate Fast walking, heavy gardening, moderate sports such as bicycling, tennis, dancing Heavy Vigorous work, sports such as swimming, running, basketball and football 1.0-2.5 60-150 2.5-5.0 150-300 5.0-7.5 300-450 7.5-12.0 450-720

  43. Energy used in a Variety of Activities Activity Energy (Cal/min) Bicycling, 15 mph Bicycling, 5mph Chopping wood Driving an automobile Eating Gardening, weeding Listening to lecture Pick and shovel work Running 5 mph Skiing, cross country Swimming, pleasure Tennis, (recreational/competitive) Walking 3-5 mph Walking up stairs 12 5 7.5 2.8 1.5 5.6 1.7 6.7 10 9-17 6 7/11 5.6 10-18

  44. DEMO: Energy from snack foods • Potato is mostly carbohydrate-ie 4 Cal/gram • But , if it is deep fried in fat, add 9 Cal per gram of fat • Burning potato chip: fat burns off • Black residue is just Carbon • Salt NaCl adds yellow colour to flame

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