Obesity Lectures 1-3

Normal weight BMI range

18.5-24.9

Overweight BMI range

25-29.9

Grade 3 Obesity BMI range

BMI greater than or equal to 40

Advantages of using BMI

Easy to calculate and interpret, cheap, generalizeable over a large group, removed most bias (sex, age). BMI doesn't take into account fitness, health and body fat.

Energy Expenditure

How much energy is spent: can be measured several ways: respirometry, calorimetry , doubly labeled water.

Health risks associated with Obesity

Increased risk for diabetes (DMT2), cardiovascular disease, stroke

IRB

Institutional Review Board: before conducting human trials, all protocols and methods must be approved by the IRB. Very stringent standards, can take a long time to get approval. Must explain who you dis-included and why.

Doubly Labeled Water

Stable isotopes of deuterium and O-18 used to determine EE through exhaled CO2 and water or only water (deuterium). Isotopes left in urine are measured with special machine. Very expensive ~$200 a glass, trial usually run for two weeks in humans to calculate BMR (basal metabolic rate).

BMI

Used to calculate weight to height ratio. Mass in Kg divided by height in meters squared.

VO2 Max

VO2 peak (volume of oxygen taken in at peak of physical activity). Measured via cardiac stress test results depend on patient's intrinsic ability, training, and determination.

Respiratory Quotient

volume of CO2 eliminated over volume of O2 used. Different types of food produce different RQ's. Pure carbohydrate metabolism: 1 RQ, Protein: 0.8-0.9 RQ, and fat 0.7 RQ

Prevalence of Obesity in US

~35% of adults are obese ~69% of adults are overweight or obese

Populations susceptible to Obesity

Gender: Women are more likely to be obese than men. Ethnicity: Blacks are most likely to be obese followed by Hispanics followed by whites

Energy Intake

How much energy is being consumed. Can be more difficult to determine EI. Why? 1. Inaccurate self reporting 2. Controlling 100% of what people eat is expensive and difficult 3. Calorie labels on food are not always accurate.

Obese BMI range

30-34.9

Grade 2 Obesity BMI range

35-39.5

Disadvantages of using BMI

Doesn't always accurately represent body fat: e.g. someone with a lot of muscle may have a BMI that classifies them as obese with a body fat percentage that does not qualify as obese.

Obesity Definition

Greater than 25% body fat for males, greater than 35% body fat for females. OR BMI greater than or equal to 30.

MONW

Metabolically Obese Normal Weight those who are insulin resistant also show: low VO2 max, central fat distribution, and low physical activity levels even if their BMI doe NOT qualify them as obese.

Respirometry

Oxygen to carbondioxide ratio used to calculate EE

Defining Obesity in Children

Percentile scale used

DXA

Scan used to measure body fat and bone density. Very accurate, considered the gold standard, used in hospitals. Can be costly and requires exposure to radiation.