weight management Flashcards
what is the SI unit (international) for food energy?
joule (J)
- energy used when a mass of 1kg is moved through 1 meter by a force of 1N
what is the non-SI unit for food energy?
calorie (cal)
- energy required to raise temp of 1g of water by 1*C
- kcal the same but 1kg of water
what is the energy balance equation?
explain it?
energy intake = energy expenditure (doesn’t change much unless high intensity exercise) +- energy stored
if intake
what does 1kcal=?
4.2kJ
how to measure total energy value of food?
bomb calorimeter:
chamber in water bath
put food in and burn it in presence of O2
heat of combustion will raise water temp and can then determine calories in that food
but protein not fully combustible (into CO2 and water) so energy not the same
what is metabolisable energy?
what is it limited by?
energy actually supplied to tissue by each food
some not digested or leaves as faeces, or nitrogen in urine
what are the atwater factors of CHO, protein, fat and alcohol?
why is it not just 1 value?
CHO - 4 kcal/g
protein - 4
fat - 9 (energy dense)
alcohol - 7
value differs for different types of the macronutrient e.g saturated and unsaturated fats and different amino acids
what are the 3 main components of energy expenditure?
1) basal/resting metabolic rate (60-70% of total energy expenditure)
2) physical activity (EEA) (25-30%) mainly made up of non-exercise activity thermogenesis (not proper exercise)
3) diet-induced thermogenesis (DIT) - increase in metabolic rate after a meal due to ensuing processes e.g digestion and absorption
describe basal metabolic rate as a main component of energy expenditure?
what are the main contributors to it?
minimum level of energy to sustain vital funcitons in the waking state
- heart and respiratory functions
- protein turnover 25% (large amount of fat free mass then high metabolic rate as lots of turnover)
- fat&carb turnover
- maintenance of ion gradients across membranes
how to measure basal metabolic rate?
in supine position (lying face up)
thermoneutral enviro
after 8h sleep and 12h fasting
describe diet induced thermogenesis as a main component of energy expenditure?
what are the 2 types?
energy required to digest, absorb, and assimilate food nutrients
1) obligatory thermogenesis - of protein (the most), fat and carbs
2) adaptive or facultative thermogenesis - increase in sympathetic nervous system activity in response to feeding
describe the thermic effect of exercise as a main component of energy expenditure?
EEA is 10% of EE in sedentary and 15-30% in athlete
describe the thermic effect of illness as a main component of energy expenditure?
examples?
exception?
injury leads to increase in basal metabolic rate
e.g mending bone fracture and third degree burns increase BMR
starvation reduces basal metabolic rate
when does obesity occur?
when energy intake>energy expenditure
over a prolonged period of time
what is BMI?
body weight in kg/height in meters^2
what is the definition of obese in terms of BMI?
obese = 30-40 BMI
what is another way of measuring obesity?
how would it define obesity?
measuring the amount of body fat, especially around abdominal region to determine risk
obesity=too much body fat as starts to accumulate in different parts of body e.g abdominal region
what is one of the main reasons for increased energy intake beyond a healthy level?
homeostatic systems of energy intake impaired
e.g don’t know when next meal is so store it all
what is the role of the hypothalamus in eating?
what happens in obesity?
internal factors influencing energy intake
hypothalamus controls hunger and satiety (stop eating)
- has desire to eat and contains pathway to stop this desire
what happens to the hypohalamus in obesity?
internal factors influencing energy intake
obesity:
becomes resistant to leptin (stop eating message) due to always eating in obesity so can eat more without being full
reduced gut hormone releasedso don’t feel full when we are
impaired hypothalamic signalling
what are 4 external factors influencing energy intake?
- psychological - reward/pleasure pathways (always room to desert), palatability
- cost - cheap foods energy dense
- convenience/time of day - snacks energy dense
- social and peer pressure
what are some risk factors for obesity?
2 main groups and subgroups of these?
- genetic
- monogenic syndromes e.g leptin deficiency due to lack of gene to produce it
- genetic susceptibility - environmental
- diet e.g fat (passive overconsumption of food), sugar and alcohol
- socio-economic status
- no physical activity
