Energy Balance & Weight Management Flashcards
What is a healthy body weight?
A healthy body weight is a weight…
- at which you are at lowest risk for morbidity or mortality
- that is easily achievable and sustainable
- that is appropriate for your age and physical development
- congruent with your family history and genetics
- that promotes healthy lifestyle activities (e.g., healthy eating habits, regular physical activity, etc…)
Every individual has his or her own individual ‘healthy body weight’.
What is BMI?
- BMI = kg/m2
- index of total body weight independent of height
What are the advantages of BMI?
- inexpensive
- easy to calculate
- quick estimate of relation to risk of disease (e.g., BMI >30 increased risk of T2D, hypertension, heart disease)
What are the disadvantages of BMI?
- doesn’t indicate how much body weight is fat
- doesn’t indicate location of body fat
- only suitable for non-pregnant, non-lactating adults
- should be used with other anthropometric assessments
How is any association between body weight and health determined?
- no single measure should be used to assess body weight
- several measures should be used to:
- assess body composition
- assess fat distribution
When focussing on nutritional assessment, data can be collected from which four different sources?
A, B, C, D:
- Anthropometric – physical body
- Biochemical – blood & tissue
- Clinical – general appearance, blood pressure
- Dietary – nutrients
What is hydrodensitometry?
Underwater Weighing - measure of body fat composition
- multiple submersions in tank of water
- compare displacement of water with land weight to determine body volume and body density (weight/volume)
- use Siri formula to accurately calculate % body fat within 2-3%
How can calipers be used to measure body fat percentage?
- repeated measures taken at several sites:
- subscapular (under shoulder blade)
- suprailiac (between rib cage and hip bone)
- triceps (back of upper arm)
- thighs
- measures are averaged and compared with standards
- body fat estimate accurate within 3-4%
What is bioelectrical impedance analysis?
- measures resistance of tissue types to low grade electrical current passed through body under normal hydration status
- fat tissue resists current more than lean tissue
- accuracy within ~4%
What is near infrared reactance?
- wand strapped to bicep, scanner held in outreached hands
- IR beam penetrates arm and is reflected back through the scanner to wand
- measure change in IR level
- fat tissue absorbs more light than lean tissue
- low accuracy; not useful
How can isotope dilution be used for measuring body fat composition?
- take baseline sample of salvia
- drink measured amount of labelled water
- wait specific amount of time then measure amount of label in second saliva sample
- lean body mass (LBM) retains more label than fat tissue
What is Dual Energy X-Ray Absorptiometry?
DEXA SCAN!
- measure the differential between two x-rays of separate energies
- full body scan used to simultaneously measure different body tissues (bone, fat-free soft tissue, fat)
- also used to measure specific tissues (e.g., bone density)
- extremely accurate
What are the recommendations for waist circumference in Canada?
How do the Canadian guidelines use both WC and BMI for recommendations of body composition?
What is Waist to Hip ratio and why is it useful?
- provides an indication of where fat is located
- Men waist:hip: <1.0 desirable
- Women waist:hip: <0.80 desirable
What is the basic energy balance equation?
BMR: basal metabolic rate
PA: physical activity
TEF: thermic effect of food
What is a direct measurement of body expenditure?
- direct measure of heat released from human enclosed in insulated metabolic chamber
How many calories make up 1 lb of body fat?
- 3500 kcal = ~0.45 kg (1 lb.) of body fat
How do we measure the energy in foods?
- bomb calorimeter – direct measure of chemical energy in bonds in food that is released in the form of heat
- use equations to determine relative efficiency of humans to extract energy when we “burn” foods
How do internal signals affect energy intake?
- feeding and satiety are controlled by the brain
- low blood glucose levels will trigger feeding
- high blood glucose will trigger satiety
- damage to the hypothalamus can result in over- eating (weight gain) or under-eating (weight loss)
Describe the internal signal ‘hunger’.
- inborn instinct
- feeding centre in hypothalamus activated causing hormone release due to lack of nutrients in GI tract (e.g., ghrelin = hunger hormone)
- contrasts to appetite – a learned behaviour – can interfere with hunger/satiety cycle
Describe the internal signal ‘satiety’.
- satiety centre in hypothalamus activated by presence of food in GI tract, distention, raised BGL, and hormonal signals (e.g., leptin = satiety hormone)
- brain signals to stop eating
How do external signals affect energy intake?
- Environmental signals:
- time of day
- sight of food
- smell of food
- location (e.g., mall, cafeteria)…
- Psychological signals:
- many stimuli:
- social influences, pressures, and situations
- mood, stressful situations…
What is an indirect measure of energy expenditure?
- Respiratory Quotient (RQ) gas exchange (O2 consumed/CO2 exhaled) used to determine relative amount of energy needed to perform exercise or to determine BMR (~5 kcal/Ltr O2)
What factors influence energy expenditure?
- Basal Metabolic Rate ~50-65%
- PhysicalActivity ~30-50%
- Thermic Effect of Food ~5-10%
What is BMR?
Basal Metabolic Rate
- ~50-65% of Energy-OUT
- “organ metabolic rate”
- respiration
- circulation
- core temperature
- metabolism
- minimum amount of energy needed at rest to sustain vital body functions
- varies for each individual
How is BMR measured?
- measured under standard conditions
- lying still
- awake
- 12-14 hour post-absorptive
- thermal neutrality
What factors influence BMR?
1. Age
- highest at 1 year (per kg body weight)
- adults: ~2% decrease per decade after 30 years
2. Growth
- increased during childhood, adolescence, pregnancy
3. Size
- height – tall, thin increased surface area, higher BMR
- weight – energy expended for BMR is lower per kg at higher weights
4. Body composition
- higher proportion of lean tissue increases BMR
- males ~10% > than females
- adult males: ~15% body weight as fat
- adult females: ~25% body weight as fat
5. Physiological state (non-standard conditions)
- fever increases BMR
- hot and cold environments increases BMR
- hyperthyroidism increases BMR
- thyroid hormones can increase or decrease BMR
- stimulant drugs: caffeine, tobacco increases BMR
- luteal phase of menstrual cycle increases BMR
- starvation/fasting/malnutrition decreases BMR
How does physical activity affect ‘energy-out’?
- ~30-50% of Energy-OUT
- varies greatly from individual to individual
- increased LBM raises BMR
- impacted by FITT principle
- Frequency
- Intensity directly proportional to Energy-OUT
- Time
- Type – different effects
- include endurance, flexibility & strength activities
What are the health benefits of physical activity?
- reduced risk for heart disease, stroke and hypertension
- reduced risk for weight gain and obesity
- reduced risk for type 2 diabetes
- potential reduced risk for colon cancer
- reduced risk for osteoporosis
- improved sleep patterns
- alleviate mental stress and depression
- 20-30 min/day offers many health benefits
Discuss the use of ATP and PCr during physical activity.
- ATP used by all cells: limited supply in muscle cells (1-3 seconds)
- PhosphoCreatine (PCr) in muscle splits and donates phosphate to regenerate ATP from ADP
- combined, stores of ATP and PCr can fuel muscle cells working at maximal effort for about 3-10 seconds, then need to turn to CHO and FAT as fuel sources
Discuss the use of carbohydrates during physical activity.
- CHO (glucose) is a ready source of energy (from glycogen stores or blood) through Glycolysis – aerobic or anerobic
- primary fuel source for quick, high intensity activities (e.g., sprinting, quick jumps)
Discuss the use of FAT during physical activity.
FAT OXIDATION (Beta-oxidation)
- fatty acids in triglycerides provide an abundant source of ATP under aerobic conditions only (no anerobic FA breakdown)
- plenty of stored TG – even in lean people
- TG supply >2X energy/gram compared with CHO
- slower oxidation process for fat compared with CHO, fat doesn’t support quick, high intensity activities
Compare the usage of fuels during different types of exercise.
Discuss the use of PROTEIN during physical activity.
- aerobic breakdown
- amino acids not used much to support cellular ATP needs for activities (account for ~3-6% of energy need)
- important non-protein function of glucogenic amino acids is their conversion to GLU (gluconeogenesis) to raise BGL during activity
- amino acids used to build and repair lean tissue after activity
- PRO needs of athletes only slightly higher than needs of non-athletes
Dicuss where & how much energy is stored for physical use in the body.
- most energy storage in body in adipose tissue as TG
- females ~25% body mass as fat
- 55 kg female ~14 kg fat mass = 14,000 g fat
- 14,000 g X 9 kcal/g ~126,000 kcal of stored energy as TG
- males ~15% body mass as fat
- 70kg male~10kgfatmass=10,000gfat
- 10,000 g X 9 kcal/g ~90,000 kcal of stored energy as TG
- smaller amount of E storage in liver and muscle as glycogen
- about 400 kcal of CHO stored as glycogen in liver and 1000- 1500 kcal of CHO stored as glycogen in muscle, dependent upon training
When is there anaerobic breakdown of CHO?
- Split-second surges of power as in the heave of a barbell or jump of a basketball player involve anaerobic breakdown of CHO.
Where does abundant energy come from?
- Abundant energy from the breakdown of fat comes only from aerobic metabolism.
What energy does low intensity long duration activities use?
- Low- to moderate-intensity aerobic exercises that can be sustained for a time (more than 20 minutes) use limited glucose and more fat for fuel.
Summarize using nutrients for energy.
- GLU:Aerobic and anerobic breakdown
- Fattyacids, Aminoacids: Only aerobic breakdown
- Glucose and fatty acids primarily used for energy; amino acids to a much lesser extent
- Glucose can be synthesized from all carbohydrates, most amino acids, the glycerol portion of TG & ethanol
- All energy-yielding nutrients consumed in excess can contribute to fat storage
- Water: necessary for catabolic reactions; keep well hydrated at all times
Discuss the importance of water regarding physical activity.
- An appropriate intake of macronutrients, micronutrients and water all support physical activity.
- To prevent dehydration and the fatigue that accompanies it, drink plenty of liquids before, during, and after physical activity.
What is TEF?
- Thermic Effect of Food
- ~5-10% of Energy-OUT
- energy used by body to process food consumed
- peristalsis, segmentation, muscle action
- production of digestive juices
- active transport absorption of some nutrients § transport, metabolism, storage of nutrients
- TEF is proportional to kcal consumed
What are minor terms usually excluded from the energy balance equation?
- temporary starvation
- extreme cold temperature
- altitude ~3000m
- trauma
Discuss dietary changes that can be made to acheive weightloss.
- choose smaller portions of lower-fat foods more often
- make nutrient-dense food choices
- avoid fad diets and “quick fix” herbal or other remedies marketed for weight loss – adequacy, balance, kcalorie control, moderation, and variety are key principles to follow
- don’t drop kcalorie intake below ~1500-1800 kcal/day – otherwise food selections become restricted and if drop <~1200 kcal/day, body slows metabolism to conserve energy
Discuss physical activity as a weightloss strategy.
- enjoy different types of physical activity every day
- initially aim for 30 minutes of activity each day
- once aerobic capacity increased, maintain an accumulated total of 150 minutes per week (minimum 10 minute intervals) of moderate-to-vigorous aerobic physical activity
Discuss behavioural changes as a weight loss strategy.
- remove tempting energy-dense foods from your regular daily habits (e.g., avoid walking by the bakery or fast food outlets, don’t shop when hungry)
- use smaller dishes and consume smaller portions
- learn which foods are high kcalorie (e.g., in restaurants, at take-out establishments) and avoid consuming them on a regular basis
- turn off the TV when eating and take time to enjoy your food
- don’t be harsh with yourself if you fail to meet your plan, but don’t give up – rethink things through, make a new and realistic plan, and try again
Discuss dietary changes as a weight gain strategy.
- consume ~500-700 kcal/d greater than EOUT
- expect to feel full
- don’t forget to eat – meals and snacks throughout the day
- try to eat a little more at each meal and/or snack
- pack healthy snacks with you throughout the day
- use larger bowls, plates, cups
- eat granola, nuts, dried fruit at end of meal
- drink healthy energy-dense beverages
- use oil in casseroles, soups, on salads
§ try a muffin instead of bread
Discuss physical activity as a weight gain strategy.
- enjoy different types of physical activity
- aim for at least 30 minutes of moderately-intense activity 5x per week
- activity can stimulate appetite
Discuss behavioural changes as a weight gain strategy.
- set aside times in your day to eat
- learn which nutrient-dense foods are higher in kcalorie – include in your diet on a regular basis
- have foods around you – in your backpack, on the kitchen counter, etc.
Discuss health issues associated with energy imbalance.
What are the functions and sources of energy?
Functions
- Maintaining basal body metabolism
- Performing work
- Processing food consumed
Sources
- foods and beverages consumed (except water)
Discuss EER.
- Goal: energy intake that maintains or attains a healthy body weight
- Balance Energy-IN with Energy-OUT to maintain a healthy body weight over time
- monitoring own body weight is best indicator of energy balance; keep well hydrated
