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Lecture

Week 11 - Weight Management.doc

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Department
Nutrition
Course
NUTR 1010
Professor
Andrea Buchholz
Semester
Winter

Description
Week 11: Weight Management Body Fat • Padding • Insulation • Energy • Fuel for muscles • Structure to cell membranes (phospholipids) • A building block for vitamin D, sex hormones (cholesterol) But, excess body fat-obesity- is associated with: • CVD, type 2 diabetes, certain types of cancer • Reproductive problems, osteoarthritis • Sleep apnea, depression • Discrimination o In general, obese people are paid less, are more likely to be unemployed, and are given poorer medical care Obesity is also: • Expensive (increased health care costs, medications) • An epidemic: in 2011, 18.3% of Canadians (4.6 million) reported that they were obese Is obesity always associated with negative outcomes? • No, some obese people are metabolically healthy o May have excess FM, but risk factors are not elevated, i.e., normal triglycerides, blood pressure, etc. o Risk of heart disease and diabetes no higher in leaner population • ~10% to 30% of the obese population is metabolically healthy o Tend to be pears vs. apples Body Mass Index (BMI) • Classifies body weight for the general healthy population • BMI = weight (kg) / height (m2) • Strengths of BMI o Easy, inexpensive, and non-invasive to measure o Can be used to identify those at risk of developing health problems Classification • Underweight: <18.5 (increased risk of health issues) • Normal weight: 18.5-24.9 (least risk) • Overweight: 25.0-29.9 (increased risk) • Obese: o Class 1: 30.0-34.9 (High risk) o Class 2: 35.0-39.9 (Very high risk) o Class 3: >40.0 (Extremely high risk) BMI Limitations • No indication of proportion of fat-free mass (FFM to FM) • Could be same weight/BMI but have different FFM/FM levels • No indication of fat distribution • That is, BMI cannot tell us where in the body fat is found Why is fat distribution important? • The “apple” distribution is associated with a greater health risk than the “pear” fat distribution Visceral fat, found more in “apples”, is fat around the organs • Associated with problems with fat and carbohydrate metabolism • Increased risk of type two diabetes, heart disease, and high blood pressure • Greater in men than women • Subcutaneous fat (under skin; on top of abdominal muscle) not associated with these same problems Waist circumference (WC) gives us an indirect measure of visceral fat • WC is more highly associated with metabolic risk than BMI • A WC >102 cm for men and >88 cm for women indicated metabolic risk • “Metabolic risk” includes high blood cholesterol, blood sugar, blood pressure, etc. “Ideal” percent body fat for good health • Men: 8% to 22% • Women: 20% to 35% • There are many methods used to measure body fat: o Some are lab-based methods (e.g., DXA, BOD POD) o Some are “field” methods (e.g. skinfold thickness, bioelectrical impedance analysis) Dual energy x-ray absorptiometry (DXA) can measure fat mass (and fat-free mass including bone) DXA • Strengths: o Measures many body components (i.e., bone, soft lean tissue, FM) o Can measure regional body composition (i.e., abdominal fat, bone in left arm, etc.) o It is reproducible and accurate • Limitations: o Client exposed to radiation (minimal) o DXA is expensive, not widely available o In Ontario, DXA must be operated by a Medical Radiation Technologist or a Radiologist BOD POD (air displacement plethysmography) • Uses displacement of air inside chamber to determine body volume • From body volume measurements, body density is determined and fat mass and fat-free mass are calculated • Strengths: o Reference standard for 2 compartment model of body composition o Accurate and reproducible in most people of all sizes and ages o Licensed personnel not required o Excellent acceptance (people like it) • Limitations: o Like DXA, expensive and not widely available o Cannot measure body fat distribution o Participants must wear bathing suit, swim cap Skinfold thickness uses calipers • Fat mass usually determined from sum of 4 skinfolds • Strengths: o Inexpensive and portable o Minimal equipment required o Minimal client burden • Limitations: o Technically difficult to perform (therefore risk of inaccurate, non- reproducible results) o Most equations used to convert skin folds to fat mass have been developed for younger, normal weight individuals Bioelectrical impedance analysis (BIA) • Measures resistance of body tissues to a low electrical current • Water conducts the current, so BIA actually measures body water • Body water is converted to fat-free mass, which is subtracted from body weight to get fat mass (FM) • Strengths: o Inexpensive o Portable o Easy to operate o Results are reproducible
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