Physiology of Feeding and Satiety

Question 1

what 2 factors have contributed to the increasing rate of GI diseases?

Answer 1

abundant high calorie foods

low energy demand foods

Question 2

what are the BMI ranges for normal, overweight, obese and morbidly obese?

Answer 2

normal = up to 25
overweight = 25-29.9
obese = 30-39.9
morbidly obese = >40

Question 3

describe the trend in obesity incidence in the UK

Answer 3

increased 3-4X since 1980s
higher death risk
same economic impact as war and smoking

Question 4

name 5 diseases that obesity can contribute to

Answer 4

type 2 diabetes
hypertension
MI
stroke
colon cancer
osteoarthritis
NAFLD (fatty liver)
dementia
sleep apnoea

Question 5

what are the 3 functions of fat?

Answer 5

energy store
prevents starvation
energy buffer during prolonged illness

Question 6

why is it difficult to lose weight in terms of brain function?

Answer 6

brain eventually views extra weight as normal so defends the extra weight as you try and diet

Question 7

how is feeding behaviour influenced by the CNS?

Answer 7

CNS influences behaviour, ANS activity (energy expenditure) and neuroendocrine system, the integration of which in the hypothalamus determines feeding behaviour

Question 8

what effect will a lesion to the medial/lateral hypothalamus have on weight?

Answer 8

medial lesion = obese
lateral lesion = lean
Due to effect on feeding beaviour

Question 9

what 3 concepts underlie the concept of the feeding behaviour control system?

Answer 9

ssatiety and signalling
adiposity negative feedback signalling
food reward

Question 10

what is satiety?

Answer 10

short term process regulating meal initiation and, termination and inter-meal frequency

Question 11

what satiety signals increase during meals to limit the size?

Answer 11

CKK = in proportion to lipids and protein
PYY3-36 = increases after meal, slows emptying
GLP-1 = inhibits gastric emptying after meal
OXM = released after meal, suppresses appetite
Obeatatin = reduces food intake

Question 12

what is the hunger signal and how does it work?

Answer 12

ghrelin (octanoregulated peptide)
produced and secreted by oxyntic cells in stomach
levels increase before and decrease after meal
stimulates food intake

Question 13

how does the hypothalamus control obesity?

Answer 13

involved in feedback loop which maintains body energy stores
signals produced in response to nutritional status
signals sensed in hypothalamus
hypothalamus acts to modulate food intake and energy expenditure via adiposity signals

Question 14

what are the 2 hormones involved in adiposity signalling and what is their function?

Answer 14

leptin
insulin
inform hypothalamus of fat status to alter energy balance (eat less and increase energy usage)
this is defective in obesity

Question 15

what is the result of a leptin or leptin receptor deficiency?

Answer 15

uncontrollable obesity

Question 16

what is leptin and what are its biological roles?

Answer 16

cytokine/pleotropic hormone secreted from adipocytes
involved in control of:
food intake, energy expenditure, fat deposition, glucose metabolism, insulin sensitivity, immune system and reproductive system.
also involved in angiogenesis, tumoourigenesis and bone formation

Question 17

what are the functions of insulin?

Answer 17

central actions = inhibits food intake and decreases body weight in rodents
lack of receptor = obesity

Question 18

adiposity signals = short term control

gut hormones = long term control, true or false?

Answer 18

false

other way around

Question 19

what is “food reward”?

Answer 19

pleasure derived from eating
important role in dopamine pathways
hedonistic aspects of food linked to fat and sugar
implicates same areas as substance abuse and rug addiction

Question 20

can leptin therapy help common obesity?

Answer 20

no

only those with rare genetic problem with leptin receptors due to leptin resistance

Question 21

what is currently the only common over the counter drug for obesity and what are its side effects?

Answer 21

orlistat
side effects = cramping, severe diarrhoea, need for vitamin supplements
not very effective

Question 22

name 4 potential anti-obesity drugs in the pipeline

Answer 22

lorcaserin
qsymia
contrive(mysimba)
liraglutide (saxenda)

Question 23

how effective is bariatric surgery?

Answer 23

very
50-60% weight loss in 1 year
good resolution of type 2 diabetes
restricts calorie intake and induces malabsorption

Question 24

what is adaptive thermogenesis?

Answer 24

induced browning of white adipose tissue as brown adipose tissue dissipates energy as heat via uncoupling protein 1 action