Exam 3 Nutrition IIEnergy Expenditure, Body Composition, and Healthy Weight

Normal

(18.5-24.9 kg/m2

Overweight

(25.0-29.9 kg/m2)

Obese, class I

(30.0-34.9 kg/m2)

Obese, class II

(35.0-39.9 kg/m2)

Underweight

(< 18.5 kg/m2)

Obese, class III

(≥ 40 kg/m2)

•Android obesity

-Apple shape (central adiposity) -Strongly associated with disease risk

•Daily energy expenditure components

-Basal metabolic rate -Physical activity -Thermic effect of food

Basal Metabolic Rate Measured by Indirect Calorimetry •Factors that influence BMR (often related to lean body mass)

-Body composition and surface area -Gender and age -Pregnancy and dietary restriction -Environmental temperature (cold-shivering; hot-sweat and increased blood circulation) Starvation (loss of lean body mass)

•Obesogens

-Interfere with hormone functions by binding to receptors and stimulating or inhibiting the signaling pathway -Promote triacylglycerol production and deposition in adipose tissue -Disrupt appetite control in the hypothalamus -Early exposure may interfere with epigenetic programming of gene regulation -Example: BPA in plastics -Other examples: parabens, sulfates, phthalates, artificial colors and flavors

Laboratory Methods for Measuring Body Composition •Dual-energy X-ray absorptiometry (DEXA)

-Involves scanning subjects with X-rays at two different energy levels -Percentage of fat mass, bone-free fat-free mass, and bone mineral can be calculated -Considered gold standard technique for diagnosing osteoporosis and osteopenia -Commonly used and widely available -Low X-ray exposure -Results highly reproducible and correlate well with other assessment methods

•Gynoid obesity

-Pear shape -Excess fat accumulates around the hips and thighs

•CCK

-Produced in small intestine in response to food intake -Binds to receptors in hypothalamus and pylorus

•Ghrelin

-Produced predominately in the stomach -Stimulates feeling of hunger

•Basal metabolic rate (BMR) represents energy expended for:

-Respiration -Heartbeat -Renal function -Brain and nerve function -Blood circulation -Active transport -Protein synthesis

•Insulin

-Suppresses hunger by acting on orexigenic and anorexigenic neurons

Basal Metabolic Rate Measured by Indirect Calorimetry Protocol •Measured

-in postabsorptive (fasted 12 to 18 hours after last meal) state, -in the morning after waking from sleep, - supine (preferably 30 minutes), -motionless, -in a thermoneutral environment -Oxygen consumption measured for 10 minutes

•Skeletal muscle requires significant energy when physically active -Accounts for

10-30% of total daily energy expenditure •Quantifying energy expenditure of physical activity -Difference between RMR (or BMR) and total energy expenditure •Alternate method -Multiply RMR by PAL (Physical Activity Level)

-RQ of 0.82 indicates -

40% carbohydrate and 60% fat

Reduced HDL-C

< 40 mg/dL (1.0 mmol/L) in men < 50 mg/dL (1.3 mmol/L) in women

The Fit3D scanner can determine body weight and composition

Infrared mapping cameras scan

Indirect Calorimetry Weir Formula

Metabolic rate (kcal per day) = 1.44 (3.94 VO2 + 1.11 VCO2) This is how the metabolic rate is determined by indirect calorimetry. The indirect calorimeter is connected to a computer that makes this calculation. know that VO2 and VCO2 are in the formula (no need to know formula)

Resting Metabolic Rate Measured by Indirect Calorimetry Protocol •Resting metabolic rate (RMR) -

More easily measured §Fast 3-4 hours §Avoid exercise 12 hours prior to testing §Rest in a reclining position for 30 minutes §Measure VO2 and VCO2 for 10 to 12 minutes (that is until the variation of measurements is less than 10%) § -Slightly higher than BMR

Adiponectin

Site of Production Adipocytes Action Protects against insulin resistance, glucose intolerance, and dyslipidemia.

Cholecystokinin

Site of Production Intestine Action Suppresses appetite and promotes satiety.

Glucagon-like peptide 1

Site of Production Intestine Action Suppresses hunger and inhibits glucagon production.

Pancreatic polypeptide

Site of Production Pancreas Action Suppresses hunger in the short term.

Peptide YY

Site of Production Small and largeintestine Action Suppresses hunger in the long term.

Ghrelin

Site of Production Stomach and duodenum Action Stimulates hunger and food intake. Promotes digestion

Leptin

Site of Production White adipose tissue Action Decreases the urge to eat and increases physical activity??? to produce a negative energy balance. Leptin resistance reported in the obese.

Insulin

Site of Production pancreas Action Suppresses hunger and stimulates the deposition of triacylglycerols in adipose tissue, which stimulates leptin.

Elevated blood pressure

Systolic ≥ 130 and/or diastolic ≥ 85 mm Hg

Energy Expended on Various Activities

The values listed in this table reflect both the energy expended in physical activity and the amount used for BMR. To Calculate kcal spent per minute of activity for your own body weight, multiply kcal/lb/min (or kcal/kg/min) by your exact weight and then multiply by the number of minutes spent in the activity. For example, if you weigh 142 pounds, and you want to know how many kcal you spent doing 30 minutes of vigorous aerobic dance: 0.062 x 142= 8.8 kcal per minute; 8.8 x 30 minutes = 264 total kcal spent. If I give you a table on an exam, know how to calculate energy spent in physical activity

Ideal Body Weight Formulas

Yellow (Hamwi) is most often used in clinical practice-

• VO2 max increases with exercise and is

a measure of cardiovascular fitness Sedentary- 30-40 Trained - 80-90

•Hormonal influences -Main hormonal target:

arcuate nucleus region of hypothalamus -Two distinct populations of neurons with opposing actions that release orexigenic and anorexigenic peptides

•Indirect calorimetry -Heat release by metabolic oxidation can be

calculated indirectly by measuring consumption of oxygen (VO2) -Expiration of carbon dioxide also measured (VCO2) -Practical, used clinically

•Using body weight as proxy for body fat less accurate at intermediate body weights •Field methods -Skinfold thickness §Measured at various sites (

e.g., triceps, suprailiac, abdominal, thigh, subscapular, using a caliper: thickness of SQ fat directly correlates with total body fat §Need to take the average of 3 measurements §Measurements should be within 5% of each other §Measurements can be entered into equations §Equations provide percentage of body fat

•Deposition of triacylglycerols causes

enlarged adipocytes AND new adipocytes are produced to accommodate more triacylglycerol molecules

-RQ of 1.0 or higher could also mean

fat synthesis or overfeeding

•RQ for individual consuming ordinary mixed diet will range

from 0.7 to 1.0

•VO2 max measures exercise capacity the point at which a further increase

in the intensity of the exercise no longer results in an increase in the volume of oxygen intake (ml 02 / kg/min)

DRI (Women):

kcal/d = 448 - 7.95 x Age (yr) + PAL (11.4 (wt)] + 619 x ht [m]) Know that DRI formula includes PAL

BMI 30

obese

BMI 25

overweight

•Growing evidence indicates link to obesity and metabolic dysfunction •90% belong to

phyla Firmicutes and Bacteroidetes -Level of Bacteroidetes increases when weight is reduced •Long-term dietary habits have significant impact on intestinal microbiota

-RQ less than 0.7 suggests

starvation; low-carb, high fat, calorie-restricted diet; or alcoholism

•Bioelectrical impedance (BIA) §Based on principle

that electrical conductivity is facilitated in fat-free tissue but impeded by fat tissue §Opposition (impedance) to the electric current is measured and predicts fat-free mass (muscles, organs, blood) §Not reliable for individuals with fluid or electrolyte imbalances §What kind of patients have fluid imbalances?

•Waist circumference used in addition to BMI

to evaluate body fatness • •Men > 40 in (102 cm) Women > 35 (88 cm) indicates risk

RQ less than 0.8 suggests patient may be

underfed

BMI <18.5

underweight

Alternative Scheme for Estimating Energy Cost of Exercise

•1.Problem: Figure out your resting energy expenditure by calculating the Harris Benedict Equation of your ht, wt, age. Remember to use cm and kg. (lb./2.2 = kg and inches x 2.54 = cm). See slide 22 •2. Divide result by hours in a day •3. Multiply hours of exercise x met-hours x #2

Alternative Scheme for Estimating Energy Cost of Exercise

•A metabolic equivalent (MET) is energy cost of physical activities as a multiple of the resting metabolic rate. •Tables are available that list the multiple for various forms of exercise. •Best used when measured RMR is available

Body Mass Index (BMI)

•BMI = Weight/Height2 -Weight measured in kg -Height measured in m

Laboratory Methods for Measuring Body Composition

•Densitometry (underwater weighing) •A method for assessment of percent body fat

Insulin Resistance

•Elevated blood glucose (hyperglycemia) •Often leads to Type 2 diabetes -Characterized by elevated insulin levels •Insensitivity to insulin seen in muscle and adipose tissue •Treatment: weight loss

Metabolic Syndrome

•Group of risk factors associated with cardiovascular disease (CVD) -Central obesity -Increased fasting plasma triglyceride -Decreased plasma HDL cholesterol -Hypertension •Underlying mechanisms related to insulin resistance •Diagnosis requires three of five conditions in Table 8.7 that follows

Predictive Equations for RMR •

•Harris-Benedict equations (1919) •Mifflin-St. Jeor equations (1990) •Know that these equations use ht, wt, age •Weight-only equations (25-30 kcal /kg for metabolic stress) •These formulas are regularly used in clinical practice when IC is not available

Thermic Effect of Food (TEF)

•Increase in energy expenditure associated with body's processing of food -Digestion, absorption, transport, metabolism, and storage of energy •10% of total energy intake •Protein in foods has greatest thermic effect -Increases energy expenditure 20-30%

-Discovered in 1994 -Hormone secreted by white adipose tissue -Interacts with hypothalamus to reduce hunger

•Leptin

The Respiratory Quotient (RQ)

•Ratio CO2 of produced relative to O2 consumed •VCO2/V02 = RQ -Characteristic for each fuel source -RQ for carbohydrate = 1.0 -RQ for fat =0.70 RQ for protein = 0.82

Doubly Labeled Water Method

•This method allows for assessment of total energy expenditure

Elevated fasting glucose

≥ 100 mg/dL.

Elevated waist circumference*

≥ 102 cm (40 in) for men ≥ 88 cm (35 in) for women

Elevated triacylglycerols

≥ 150 mg/dL (1.7 mmol/L)