Metabolic and Endocrine Mechanisms of Food Intake Regulation Flashcards
catabolism:
process that breaks down food molecules using oxygen, releasing stored energy
anabolism:
process that builds food molecules into complex chemical compounds
thermogenesis:
energy out
basal metabolic rate:
rate of metabolism when a person is lying down, is awake, is not digesting food, and the environment is comfortably warm
Total metabolic rate:
total amount of energy, expressed in calories, used by the body per day
Factors that effect BMR:
- size (SA)
- sex
- body comp
- age
- amount of thyroid hormone
- miscellaneous
Factors that effect TMR:
- BMR
- exercise and all kinds of muscular activity
- food intake (TEF)
- environmental temperature
thermic effect of food:
acceleration of GI tract functioning in response to food presence (releases heat)
physical activity:
voluntary movement of skeletal muscles
adaptive thermogenesis:
- adaptation to dramatically changing circumstances
- extra work done by body
- amount expected is extremely variable
- not included in energy requirement calculations
What 3 components make up thermogenesis and by how much?
- RMR (~60%)
- thermic effect of exercise and spontaneous activity (~30%)
- TEF metabolism (~10%)
food intake:
energy in
Sustaining satiation and satiety:
- protein has highest satiety
- fat can also increase satiety
- fibre has high satiation
hunger:
physiological response to nerve signals and chemical messengers (hypothalamus-induced)
satiation:
causes you to stop eating during a meal
satiety:
stops you from eating after a meal
satiating:
the power to stop you from eating
BMI:
- body mass index
- relative weight for height
- health related classifications
BMI =
weight (kg)/height (m)^2
Healthy BMI:
18.5 to 24.9 in adults
BMI is not a measure of ____ _____.
body composition
Types of body fat:
- visceral fat (central obesity)
- subcutaneous fat
waist circumference:
- indicator of fat distribution and central obesity
- waist to hip ratio
Indicator of obesity: waist circumference:
- women: greater than 35 inches
- men: greater than 40 inches
Disruption or imbalance of metabolism:
- inborn errors of metabolism
- metabolic complications from other conditions
inborn errors of metabolism:
genetic conditions involving deficient or abnormal metabolic enzymes
Metabolic complications from other conditions include…
- hormonal imbalances
- eating disorders
Eating disorders:
- anorexia nervosa
- bulimia/bulmarexia
- protein-calorie malnutrition
Obesity:
abnormally high proportion of fat in the body
Metabolic functions of the liver:
- processes blood immediately after it leaves the GI tract
- removes toxins from the blood
- helps to maintain normal blood glucose levels
- site of protein and fat metabolism
Fat metabolism:
- primarily an energy good
- converted to glucose by catabolism
- excess fat anabolized to form adipose tissue
Protein metabolism:
- catabolized for energy after depletion of carbohydrate and fat stores
- amino acids broken apart and converted to glucose via gluconeogenesis
Hormone secretion is controlled by _____ ____.
homeostatic feedback
Negative feedback:
mechanisms that reverse the direction of a change in a physiological system
Positive feedback:
- uncommon
- mechanisms that amplify physiological changes
2 types of pancreatic islets:
- glucagon
- insulin
Glucagon is secreted by ____ cells.
alpha
Insulin is secreted by ____ cells.
beta
Glucagon function:
increases blood glucose levels by accelerating liver glycogenolysis
Insulin function:
- regulates availability of all key metabolic fuels
- decreases blood glucose levels by accelerating the movement of glucose out of the blood into cells
2 obesity related hormones:
- ghrelin
- leptin
Ghrelin is secreted by ….
the gut
Leptin is secreted by….
adipose tissue
Ghrelin function:
- increases appetite
- decreases EE
- promotes positive energy balance
- inverse correlation with body weight
- roles in the body beyond energy regulation
Leptin function:
- acts as a hormone in hypothalamus
- suppresses appetite
- increases EE
- promotes negative energy balance
Genetics and epigenetics of leptin:
- genetic deficiency of leptin or genetic mutation (rare)
- leptin resistance (fructose consumption)
- letpin injections
The unsustainable diet vicious cycle:
- decision to lose weight
- make drastic diet and exercise changes for quick results
- short-term progress starts to slow down
- dig deeper and make more unsustainable changes
- hit a wall, progress stops and motivation withers away
- fall off wagon, quit dieting and pack weight back on over time
Rudolf Clausius found that….
- energy can neither be created nor destroyed
- first law of thermodynamics
First law of thermodynamics =
caloric intake - EE = change in the total energy in the body
CALERIE study:
long term effects of reducing energy intake
Hormonal adaptations to long term caloric restriction in humans:
- reduces insulin
- reduces leptin
- increases cortisol
- reduces adiponectin
Studies….
.
Glycemic index:
how much blood glucose levels are raised by food
Glycemic load:
how much of the food will raise blood glucose levels in the body
Diogenes study:
effects of glycemic load on body weight
Framingham State Food study:
effects of macronutrient composition on EE
Aim of Framingham State Food study:
to evaluate the effect of 2 diets varying in carb to fat ratio on EE during weight loss maintenance over 5 months in a feeding study
Short term feeding studies:
- digenes study (6 months)
- Framingham State Food study (5 months)
Long term feeding studies:
- POUNDS LOST study (24 months)
- DIRECT study (24 months)
- DIETFITS study (12 months)
Sequencing type of foods:
- eat non-ultraprocessed footds
- eat lower in calorie density FIRST (eg. start meals with soup and/or salad)
- eat earlier in the day
Don’t drink your calories:
- liquid calories have little satiety
- eat your fruits and veggies, don’t drink them
