Unit 6 Flashcards
Energy Balance
energy in =energy out
- a shift in balance causes weight change
- rapid changes are gradual
excess energy stored as fat
- fat is used as fuel between meals
- 20% of lost weight is lean mass
- to lose 1 pound, need to expend extra 3500 kcals than your body needs
- all gets broken down to acetyl CoA and turned to fat
Appetite
- psychological
- cues, after dinner you smell dessert and are no longer full.
- environmental impact on our appetite
Energy In: food consumption
bomb calorimetry
- as foods burn - heat, CO2 and water
-calc the cals from energy-yielding nutrients
- amount of heat/how it burns = how many cals
1kcal of energy needed to heat up 1 kg of water by 1 degree
Hunger
- physiological response - body telling us we need nutrients, nerve impulses and chemical messengers interacting w brain via hypothalamus.
Satiation
stop eating, feeling of fullness
- exercise - makes you not wanna eat
Satiety
- do not start eating again
- overriding factors - stress, boredom, socialization, easy access
Energy out: components of energy expenditure
thermogenesis: production of energy - releasing heat
- basal metabolism - amount of energy body needs every day to maintain base
RMR- resting metabolic rate
BMR- basal metabolic rate. Very base rate of food you need. Measured first thing in the morning
Food consumption
thermic effect of food -> warm feeling after eating. Body needs energy to digest and absorb nutrients. Normal meal doesn’t raise too much. More w a big meal
adaptation responses
metabolism during an infection.
metabolism is higher, body is trying to keep homeostatic state
Factors influencing energy out
- height - higher metabolic rate
- growth - growing ppl have higher metabolic rate
- body comp- more energy needed to maintain fat than muscle. therefore men have higher metabolic rate
- hormones
- stresses
- environmental temp
- smoking increases BMR
- caffiene
factors that decrease the BMR
- age
- fasting/starving: slow down rate to maintain healthy
- malnutrition
- sleep - lower when sleeping
Estimating energy requirements
influenced by:
- sex
- growth
- age
- physical activity
- body comp and size
Physical activity factors
Sedentary: typical daily activities
Low Active: 30-60 mins moderate activity
active: 60 mins or moderate activity or more
very active: 60 mins of moderate activity and 60 mins vigorous activity or 120 moderate
BMI calculation
relative weight for height BMI = weight (kg) height (m^2) underweight: <18.5 healthy weight: 18.5-24.9 overweight: 25.0-29.9 obese: 30.0+
Muscle mass
BMI doesnt include muscle mass
Body fat distribution
- important information for disease risk
- ideal amount of body depends on sex
- females have more fat comp than males, need more to survive
Fat distribution
visceral fat: the real problem for metabolic diseases
- central obesity
subcutaneious fat
Waist circumference
Indicator of visceral fat - fat surrounding organs
- women: >25in
- men >40 in
Health risks associated with body weight and body fat
- body weight and fat distribution and fat distributed correlate with disease and life expectancy
risks associated with being underweight
fighting against wasting diseases (cancer)
menstrual irregularities and infertility
osteoporosis and bone fractures
BMI and mortality
BMI 22.5-24.9 optimal
BMI 30-34.9 = 3 years loss of life
BMI >40 = 10 years loss of life
Skin Folds
- estimates body by taking caliper, pinching skin and measure thickness of roll at different landmarks
Hydro Densitometry
weight yourself on land and in tub of freezing cold water, dunk yourself completely under water
- difference between 2 weights is indicative of body volume
Bioelectrical impedance
- done at the mall, step on smth and have low electrical current through body
- electrode on finger and toe, current up and down body, speed of current is body comp
Air displacement plethsmography
determine volume of air displaces when getting into closed air space
DEXA duel Energy x-ray absorptiometry
- not gold standard
- one of the best ones
- 2 x-rays, based on speed it determines bone mass, fat mass and lean tissue
- gold standard for bone mass
Health risks associated with body weight and body fat
- obesity is a designated disease
- many costs
increases risk for many chronic conditions - CVD
- diabetes
- cancer
- inflammation and metabolic syndrome
Fat cell development
energy in>energy out
- stores in fat cells of adipose tissue
- body fat reflected in the number and size of fat cells
- in growing years, fat cells grow most rapidly
- obese individuals have more fat cells
energy out>energy in
- fat cells size decrease, no change in # of cells
Fat cell development pt 2
energy out>energy in
- fat cells size decrease, no change in # of cells
1. during growth, fat cells increase in number
2. when energy intake exceeds expenditure, fat cells increase in size
3. when fat cells have enlarged and energy intake continues to exceed energy expenditure, fat cells inc
4. with fat loss, the size of fat cells shrinks but not the #
Set point theory
- body likes to maintain homeostasis
- role of hypothalamus and other regulatory centres
- body tries to adjust to original weight
- said to be multiple set weights, becomes easier to gain/lose weight to reach set goal
Leptin
Obesity gene
- codes for leptin protein - produces in adipose tissue
- leptin acts as a hormone in hypothalamus
- promotes negative energy balance
- suppresses appetite
- increases energy expenditure - mutations are rare
- leptin resistance
Causes overweight and obesity
- environment
- interacts with genes
- environment = all circumstances that we encounter daily
- overeating is an issue too
- convenience
- large serving sizes, packages and ready-to-go meals
Video
- 10000 years ago, agriculture and domestication of animals changes
- in old egypt they used to spend 95% of time on agriculture whereas we have no problem in getting food
- late Miocene and early pleistocene 1.5 mil yrs ago
- shift from unprocessed plant foods to deliberate hunting of animals, deliberate game drives - diets in locations dominated by single cereals
how does the cost of food influence food choices
- healthy food is expensive
- unhealthy food is cheap and easily accessible
- cheap choice does not equal healthy choice
Then and now: causes of overweight and obesity
physical activity is fostered
- sedentary behaviours
- replace more vigorous activity
- we used to work/play outside
Health risks
indicators: BMI, waist circumference, disease risk profile
- motivation is key to success
- weight loss recommended for overweight
- 2+ risk factors for disease
- life-threatening disease present
if ppl have 2+ risks of disease they are recommended to lose weight
Perceptions and prejudices pt 1
assumption that everyone can lose weight - will power and hard work social consequences of obesity - discrimination - judgement on appearance - laziness, lack of self-control
Perceptions and prejudices pt 2
Physiological problems
- embarassment
- rejection, shame, depression
Problems
Dangerous intervention - some believe weight loss = happiness weight loss schemes flourish - few are effective - many are dangerous -unsubstantiated claims and deceptive testimonials
The Oz effect
a lot of supplements that say they dont have stuff in them, don’t have that but they have stuff they don’t list
why is weight loss so hard pt 1
- hard labour to get food, not just a drive thru
- unpredictable food supple with starvation being a problem a long time ago
- ppl have a strong desire for sugar sat and food variety. our brain is telling us that we are existing in a place where food is scarce.
- ## metabolism and brain want food to survive
why is weight loss so hard pt 2
- ice cream > broccoli
- thrifty metabolism -> make good use of cals
- ppl who eat and eat have fast metabolism
- brain tells body we may need food later so we keep eating
- eating becomes a priority, some can fight it off and maintain normal weight
Weight-loss strategies
successful strategies
- small changes
- moderate losses
- health benefits occur with modest weight loss
- incorporate healthy eating and physical activity into days
- 25% of lost weight is muscle mass
weight loss strategies: eating plans
- realistic energy intake
- deficit of 500-1000cal/d
- promotes fat loss, retention of lean mass
emphasize nutritional adequacy
watch your portion sizes
lower density foods - fibre
water- we think of thirst as hunger.
Physical activity
benefits of combining diet and physical activity - lose more fat - retain more muscle - regain less weight benefits to weight loss - increased metabolism - appetite control - psychological benefits
Physical activity and weight loss
exercise alone will lead to minimal weight loss
dose: ~60min/d
- have to monitor energy intake
- maitenece of lean body mass
- improved fitness
- independent effect on health parameters
How many cals do I burn in an exercise session
7 cals/min
How long to lose 1lb
he does this exercise 5x/week how long would it take him to lose 1lb
- 3500kcals/1lb
- 3500/212=16/7
16. 7 sessions/5 = 3.3 weeks
Behaviours and attitudes
change behaviors - keep records, write down what you do - set small, specific goals cognitive skills - problem-solving techniques - replace negative thoughts personal attitude - relationship with food
Weight loss registry
- largest prospective study of long-term successful weight-loss maitenence
- tracking over 10,000 people
- average weight loss- 66lbs kept off for 5.5 yrs
how: modified food intake, increased physical activity
How do they keep the weight off
- eat small portions
- eat breakfast
- by physically active
- weigh periodically
- watch <10 hrs a week of tv
