Healthy Weight Maintenance Flashcards
Evaluating Body Weight
Use body mass index = weight (kg) over height (m) squared.
Body composition
Fat distribution
BMI
Weight to height ratio (kg/m2)
Minimally invasive.
Limitations with athletes as if you are too muscular for your height, you will be labelled as overweight even if you aren’t.
BMI is directly associated morbidity and mortality
-as BMI increases, morbidity and mortality go up.
-directly go up with males, but females is not directly related.
Body Composition
Percentage of mass accounted for by fat and lean tissue (2 compartment model).
Common 2 compartment techniques include underwater weighing (must ensure no air bubbles/pockets), skinfolds, bioelectrical impedance analysis (must control for hydration).
Dual Energy X absorptometry (DEXA) is a 3 compartment model where it takes into account bone density and can look at muscle and fat too.
Fat Distribution
Waist to hip ratio (WHR) = ratio fo waist compared to hips.
-waist circumference measured at narrowest part of the waist, between the lowest rib and iliac crest.
-hip circumference measured at the widest area of the hips at the greatest protuberance of the buttocks.
High risk for men = WHR >1
High risk for women = WHR >0.85
Increased abdominal fat is directly associated with morbidity and mortality among men and appears even more so among women.
Physiology of Fat Cells
Overweight children develop more fat cells.
Extra fat cells develop in the abdomen.
Abdominal fat is more sensitive to hormones.
Metabolically active fat cells rapidly store and release fat.
Fatty acids get dumped almost directly into liver.
Fatty acids dumped on the liver increase LDL and decrease HDL.
Elevated free fatty acids in the blood induce insulin resistance.
What are some big ideas with weight maintenance?
Variety of ways to evaluate body weight.
Fat distribution varies among men and women.
Abdominal obesity is associated with disease.
Energy Balance
Energy intake = energy expenditure
Environmental factors disrupt this balance.
Weight is maintained when isocaloric balance where calories in = calories out.
Weight loss when negative caloric balance where calories in < calories out.
Weight gain when positive caloric balance where calories in > calories out.
Components of Total Energy Expenditure
Includes…
-basal metabolic rate (BMR) = ~30%
-thermic effect of food = ~10%
-activity energy expenditure = ~60%
BMR
Energy to maintain body function
Influenced by thyroid hormones and muscle mass.
After 30, BMR declines ~3.5% per decade due to loss of muscle mass.
Factors Increasing BMR
High lean body mass
Greater height
Younger age
Elevated thyroid hormones
Acute stress (exercise, frightened, chronic stress, fever/illness
Pregnancy and lactation
Stimulants (coffee, tobacco)
Factors Decreasing BMR
Lower lean body mass
Lower height
Older age
Depressed thyroid hormones
Starvation, fasting, caloric restriction
Television (when watching TV, we can decrease BMR)
BMR and Caloric Restriction
Caloric restriction decreases BMR.
Results in a 6-20% decrease in BMR among obese adults and adolescents.
BMR returns to normal levels once energy balance is achieved.
Thermic Effect of Food
Energy expended digesting, transporting, storing, and metabolizing nutrients.
5-10% of a mixed meal (25-50 kcal of 500 kcal meal)
Fat requires little energy to digest, transport, and store.
Activity Energy Expenditure
Body movement/muscular work = highly variable
Metabolic Equivalent (MET)
Standardized approach for quantifying activity energy expenditure.
1 MET = 1kcal/kg/hr = energy cost of sitting quietly
1 MET = 3.5 ml/kg/O2
3 MET = moderate physical activity = 3 times the energy cost of sitting.
Activities involving more/larger muscle groups expend more energy
