Obesity & Weight Management Flashcards
1 lb body fat = cal
3500 cal
Carbs, protein and fat go in, and
RMR Physical activity and TEF go out
Balance of energy intake and expenditure
–» body weight stability
Birth: how many fat cells?
5-6 billion fat cells.
Critical Times for increase in fat cell #:
late childhood/early puberty & 3rd trimester of pregnancy;
Fat cell # set by age 20s, except for pregnancy.
Healthy adult: fat
Overweight adult: fat
Severe obesity: fat
25-40 billion fat cells
70-80 billion
Up to 250-300 billion (Obese individuals also have enlarged fat cells, up to 3x size of healthy weight person’s fat cells.)
do fat cells have a life span?
Fat cells do have a lifespan & undergo turn-over, but are replaced 1-for-1 immediately.
Therefore weight loss leads to reduction in fat cell size, but not #.
Classification of Overweight
and Obesity in Adults BMI
Underweight < 18.5
Normal Weight 18.5-24.9
Overweight 25-29.9
Obesity ≥ 30
Class I 30-34.9
Class II 35-39.9
Class III ≥ 40
(Obese = 20% or more above ideal body weight)
The problems with BMI
- “Michelin Man” vs. “The Terminator”
Fat vs. muscle mass not distinguished – the latter classified as overweight/obese due to excess muscle. What % of general population look like The Terminator? - “Apples” vs. “Pears”
Fat in abdominal region associated with much greater risk of disease & early mortality, vs. peripheral or lower body fat. Two individuals of same BMI could have very different body shapes = different risk of disease & early mortality. - Does not always change with lifestyle change
Increased PA & improved health not always correlated with BMI ∆. Substantial health benefits even if no weight loss.
BMI is used to find weight status in
population studies
Currently about 62% of Canadian adults (age 18-79) are living with
overweight/obesity:
31% of Canadian youth ages 5-17 y
are living with overweight/obesity
Age & Sex differences (5-17)
Age 12-17: 37% overweight/obese
Age 5-11: 26% overweight/obese
Girls 12-17: 18% overweight, 12% obese
Girls 5-11: 19% overweight, 9% obese
Boys 12-17: 23% overweight, 21% obese
Boys 5-11: 14% overweight, 8% obese
Boys: 15% obese
Girls: 11% obese
Boys & Girls: 19% overweight
Underweight
15% or more below ideal BW
BMI < 18.5 kg/m2
Potential health problems: Respiratory conditions, reduced fertility, immune suppression, nutrient deficiencies
Anorexia nervosa & Bulimia nervosa
Inadequate reserves to fight wasting diseases e.g. cancer, digestive disorders
Menstrual irregularities
Risk of low birth weight babies
Osteoporosis
Increased BMI will lead to increased mortality rates in…
Cardiovascular disease (heart attack, failure)
Cerebrovascular disease (stroke)
Type 2 diabetes
Cancer (breast, colon, prostate, endometrial)
Waist Circumference
Estimates abdominal/visceral obesity, which has a stronger association with type 2 diabetes & CVD than BMI. Used in combination with BMI, provides a more robust index of overall obesity-related health risk than BMI alone.
WC cut-offs:
>102 cm men
>88 cm women
Canadian Avg:
Males: 97.5cm
Females: 90.5cm
Canada (2007-09)
BMI : 24% adults obese.
WC : 37% adults abdominally obese.
4 types of fat
Subcutaneous Fat
Visceral fat
Ectopic Fat
Intermuscular fat
Subcutaneous Fat –
Located just beneath skin.
Visceral fat
(abdominal fat) – Located in abdominal cavity surrounding & protecting organs.
Ectopic Fat
Located on or within organs e.g. heart, liver, brain.
Intermuscular fat
fat stored in the muscle tissue
Measuring types to find fat percentage
Hydrostatic (underwater) weighing
DEXA
Air-Displacement Plethysmography (“Bodpod”)
Bioelectrical Impedance Analysis (BIA)
Skinfold measurements
Hydrostatic (underwater) weighing
Assesses body volume by H20 displacement, to calculate body density. Muscle more dense so it “sinks”, weighs more, vs. fat less dense so it “floats”, weighs less.
DEXA
Body’s absorption of 2 different x-ray beams: fat, bone mineral, other fat-free mass have different absorption properties.
