GI: Nutrition - Energy (Dr. Skildum - 1 hr)
A healthy woman ate a meal of mixed carbohydrates, fat and protein on monday evening, then had her respiratory quotient (RQ) measured by indirect calorimetry. She did not eat anything for three days, and had her RQ measured again on Thursday. What happened to her RQ from Monday to Thursday? A) Decreased B) Stayed the same C) Increased
A) Decreased -she is switching from oxidizing carbs in the fed state to oxidizing fat in the starved state.
A male patient presented with a BMI of 33 kg/m2 and a waist circumference of 47 inches. What dietary therapy would you consider most helpful? A) Decreased intake of total calories B) The same amount of total calories, but substitution of carbohydrates for fat C) Increased intake of total calories D) The same amount of total calories, but substitution of protein for fat E) The ice cream and sherry diet
A) Decreased intake of total calories
The basal metabolic rate (BMR) is best explained by which one of the following statements? A) It is equivalent to the caloric requirements of our major organs and resting muscle. B) It is generally higher per kilogram of body weight in women than in men. C) It is generally lower per kilogram of body weight in children than in adults. D) It is decreased in cold environments. E) It is approximately equivalent to the daily energy expenditure.
A) It is equivalent to the caloric requirements of our major organs and resting muscle.
Which dietary carbohydrate's structure most resembles glycogen? A) amylopectin B) amylose C) fructose D) galactose E) trehalose
A) amylopectin
At non-protein RQs above 0.85, the primary fuel for respiration is. . . A) carbohydrates. B) protein. C) fat.
A) carbohydrates.
The hormone that promotes fasted state metabolism is _____________. One of the pathways it promotes is ____________. A) glucagon; gluconeogenesis B) epinephrine; glycolysis C) cortisol; urea cycle D) insulin; protein synthesis E) aldostone; glycogen storage
A) glucagon; gluconeogenesis
The subject is 25 years old, weighs 88 kg, and is 170 cm tall. How many calories would he need to eat each day to sustain his current weight?
Approach #1: a. Estimate his Resting Energy Expenditure or Basal Metabolic Rate (e.g. using the Harris-Benedict formula) -REE = 66.5 + (13.75 x kg) + (5.003 x cm) - (6.775 x age) = 1,958 kcal/day b. Add a multiplier of the REE (generally from 1.2 to 2.0) to account for physical activity and the thermic effect of food to estimate his total caloric requirements. -1,958 x 1.25 = 2,448 kCal/day Approach #2: Consult a table of dietary recommendations (from a reliable source) -Image: Male age 19-30, sedentary lifestyle should require 2,400 to 2,600 kCal/day.
A 43 year old male is 5'10" tall and weighs 170 pounds and doesn't exercise. He wants to maintain a healthy weight without changing his level of physical activity. How much would you recommend he eat each day? A) 1124 kcal/day B) 1873 kcal/day C) 2159 kcal/day D) 2567 kcal/day E) 3423 kcal/day
B) 1873 kcal/day B.E.E. = 66.5 + (13.75 x kg) + (5.003 x cm) - (6.775 x age) A) 170 lbs = 77.11 kg (170/2.21 = 77.11) B) 5'10" = 177.8 cm (5.8 ft x 30.48 = 177.8) leads to... BEE = 66.5 + (13.75 x 77.11) + (5.003 x 177.8) - (6.775 x 43) = 1724.97 x 1.1 so about 1873
When a person is burning fat for the majority of his energy, his RQ will be lower than if he were using mostly carbohydrates. This is because fat is more. . . A) Oxidized B) Reduced C) Delicious
B) Reduced
In which metabolic state is the urea cycle the most active? A) fed B) fasted (overnight) C) starved (3 days) D) starved (6 days)
B) fasted (overnight)
What is basal metabolism? What are the factors that affect someones Basal Metabolic Rate (BMR)?
Basal metabolism is expressed as the Basal Metabolic Rate (BMR) or the closely related Resting Metabolic Rate (RMR). Basal metabolism includes the energy needed to sustain cellular and organ function while at rest. Factors that affect BMR are: A) Gender (males have a higher BMR) B) Body temperature (fever increases BMR) C) Environmental temperature (BMR increases with cold exposure) D) Thyroid hormone (BMR is increased with hyperthyroidism) E) Reproduction (BMR increased with pregnancy & lactation) F) Age (BMR decreases with age) BMR represents the ratio of metabolically active tissue to metabolically inactive adipose.
How do you calculate BMI? What is considered underweight or overweight?
Body Mass Index (BMI) = Weight (kg) / Height2 (cm) BMI < 19 is underweight BMI > 25 is overweight
How is metabolism measure? Is this practical for humans?
Direct calorimetry is the gold standard. Is this practical for humans? NO!
Carbohydrates account for ~50% of the calories in the Western diet. Glucose is the main carbohydrate circulating in our blood and used for fuel by our cells. What fraction of the total calories in a Western diet are from glucose? A) 40% B) 30% C) 20% D) 10% E) 0%
E) 0% We never take in carbs in the form of glucose. Instead we take carbs and break them down into glucose
Which molecule's carbon is the least oxidized? A) alanine B) fructose C) glucose D) oleate E) palmitate
E) palmitate is fully unsaturated- it has highest ratio of carbon to non-carbon
Compare and contrast Fats, Proteins, and Carbohydrates in what you would see for indirect calorimetry and their oxidation states
Fat: -*Least oxidized (most reduced) dietary fuel* -Requires *more* O2 inhaled for each CO2 exhaled -*RQ is lowest* Protein: -Oxidation state in between carbohydrate and fat -RQ is intermediate between carbohydrate and fat Carbohydrate: -*Most oxidized dietary fuel* -Requires *less* O2 inhaled in for each CO2 exhaled -*RQ is highest*
Indirect calorimetry of Tristearin (Fat)
Fat: 9 kcal/g Complete oxidation of two molecules of tristearin: 2 C57H110O6 + 163 O2 --> 114 CO2 + 110 H2O RQ = 114 CO2 / 163 O2 = 0.70 Ideal gas law: PV = nRT A) At equal temperatures & pressure, mols of gas is proportional to volume
How is metabolism measure in humans?
Indirect calorimetry Indirect calorimetry measures: A) The volume of inspired and expired air B) The concentrations of O2 and CO2 in the inspired and respired air
How does Indirect Calorimetry used to tell what fuel a person is using? What else can it be used to estimate?
Indirect calorimetry can also be used to estimate a person's basal metabolic rate.
Harris-Benedict Equation
This calculator uses the Harris - Benedict equation to calculate BMR. It includes a multiplier to account for physical activity or recovery from injury. B.E.E. = 66.5 + (13.75 x kg) + (5.003 x cm) - (6.775 x age) Total Caloric Requirements equal the B.E.E. multiplied by the sum of the stress and activity factors. Stress plus activity factors range from 1.2 to over 2.
How, as a whole, is metabolism quantified?
Basal Metabolic Rate (BMR) kcal/day or Resting Metabolic Rate (RMR) kcal/unit of time A) RMR is similar to the BMR, but under less standardized conditions. Resting Energy Expenditure (REE) kcal/day A) REE is the BMR plus DIT (diet induced thermogenesis). (DIT may be ignored, or may be estimated as 0.1 x BMR) Daily Energy Expenditure (DEE) kcal/day A) DEE is the REE plus energy expended in physical activity, wound repair, etc. B) DEE = REE x 1.2 for a healthy sedentary adult C) DEE = REE x 1.4 for a healthy active adult D) DEE = REE x 1.6 for recovering from trauma Image: Thermoregulation is usually a wash- sometimes we get energy from our environment and sometimes we have to use energy to maintain temperature.
The subject is 25 years old, weighs 88 kg, and is 170 cm tall. The subject is eating 300 kCal / day, half as protein. Will he lose adipose mass, muscle mass, or both?
Protein has 4 kCal per gram A) (150 kCal protein)/(4 kCal/gram) = 37 grams protein Approach #1: Conduct a nitrogen balance study Approach #2: Consult a table from a reputable source to estimate how much protein is required per day The RDA for protein is 56 g per day. We can conclude that the subject is in negative nitrogen balance and will lose muscle mass.
Indirect calorimetry of Protein
Protein: 4 kcal/g Oxidation of protein to carbon dioxide, water, sulfur dioxide, and urea: C72H112N18O22S+ 77 O2 --> 63 CO2 + 38 H2O + SO3 + 9 CO(NH2)2 RQ = 63 CO2 / 77 O2 = 0.818
A 28 year old research subject weighed 77 kg and was 173 cm tall. In the fasted state, while mentally and physically relaxed, he consumed 15.7 L of oxygen per hour and expired 12.0 L of carbon dioxide. What is his RQ value? What is his basal metabolic rate (BMR)?
RQ = (12.0 L) / (15.7 L) = 0.7643 At RQ = 0.7643. . . A) Burning 81% fat, 19% carbs B) Using 4.751 kcal/L of O2 or 6.253 kcal/L of CO2 each hour. (15.7 L O2/hour) (4.751 kcal/L) (24 hours) = 1790 kcal/day (12.0 L CO2/hour)(6.253 kcal/L) (24 hours)= 1801 kcal/day
How does Indirect calorimetry measure substrate utilization?
RQ for utilizing a typical meal of fat, carbohydrate and protein = 0.85
How does Physical Activity affect our Basic Metabolic Rate?
While BMR remains relatively stable, the amount of energy dedicated to physical activity varies widely from person to person, and day to day. The energy of physical activity is often expressed as a 'multiplier' over the BMR. The multiplier ranges from 1.0 for supine rest to 7.0 for heavy exertion.
A 25 year old male pharmacy student weighs 88 kg and is 170 cm tall. He decided to lose weight by eating only 300 kcal/day of a dietary supplement that provided half the calories as carbohydrate and half as protein. In addition, he consumed a multivitamin supplement and several glasses of water per day. After three days of this diet, which statement best represents the student's metabolism? A) His protein intake met the RDA for protein B) His carbohydrate intake met the fuel needs of his brain C) Both his adipose mass and his muscle mass decreased D) He remained in positive nitrogen balance E) He developed severe hypoglycemia
C) Both his adipose mass and his muscle mass decreased Protein intake is 150 kcal; protein has 4 kcal/g 150/4 = 37 g. RDA for protein = 0.8g/kg body weight. 88*0.8 = 70.4 Carbohydrate intake is 150 kcal; carbs have 9 kcal/g 150/9 = 16.7 g Brain uses 150 g glucose per day. He is breaking down protein to produce glucose, so he must be in negative nitrogen balance. He has plenty of gluconeogenic precursors so he shouldn't be hypoglycemic
What is this structure? (see other side) A) amylose B) anandamide C) phosphatidylinositol-phosphate (PIP3) D) phosphatidylcholine E) acetyl CoA
C) phosphatidylinositol-phosphate (PIP3)
Indirect calorimetry of Glucose (Carb)
Carbs: 4 kcal/g Complete oxidation of one molecule of glucose: C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O RQ = 6 CO2 / 6 O2 = 1.00
The hormone that promotes fuel storage after a meal is _____________. One of the pathways it promotes is ____________. A) glucagon; gluconeogenesis B) epinephrine; glycolysis C) cortisol; urea cycle D) insulin; protein synthesis E) aldostone; glycogen storage
D) insulin; protein synthesis
How does our consumption of food related to our energy needed to survive? What are the components of our Daily Energy Expenditure (DEE)?
Ideally, *the amount of energy we consume should match our daily energy expenditure (DEE). * The components of the DEE are basal metabolism, physical activity, and the thermic effect of food.
When determining our daily energy expenditure (DEE), how does one take into effect the "Thermic" effect of food?
The energy required to digest, absorb, distribute and store nutrients is referred to as diet induced thermogenesis (DIT) or the thermic effect of food (TEF). DIT varies according to the composition of our diet. In a typical western diet, about 10% of the potential energy is dedicated to DIT. DIT is often ignored. A) The DIT can be ignored because when using the rough estimates of 9 kcal/g for fat, 4 kcal/g carbs and 4 kcal/g protein slightly overstates their actual caloric value.
The subject is 25 years old, weighs 88 kg, and is 170 cm tall. Is diet change warranted?
Yes! BMI = (weight) / (height)2 = (88 kg) / (1.7 m)2 = 88 / 2.89 = 30.4 'normal' BMI is between 18.5 - 24.9
