Physiology of Feeding and Satiety Flashcards
what 2 factors have contributed to the increasing rate of GI diseases?
abundant high calorie foods
low energy demand foods
what are the BMI ranges for normal, overweight, obese and morbidly obese?
normal = up to 25
overweight = 25-29.9
obese = 30-39.9
morbidly obese = >40
describe the trend in obesity incidence in the UK
increased 3-4X since 1980s
higher death risk
same economic impact as war and smoking
name 5 diseases that obesity can contribute to
type 2 diabetes hypertension MI stroke colon cancer osteoarthritis NAFLD (fatty liver) dementia sleep apnoea
what are the 3 functions of fat?
energy store
prevents starvation
energy buffer during prolonged illness
why is it difficult to lose weight in terms of brain function?
brain eventually views extra weight as normal so defends the extra weight as you try and diet
how is feeding behaviour influenced by the CNS?
CNS influences behaviour, ANS activity (energy expenditure) and neuroendocrine system, the integration of which in the hypothalamus determines feeding behaviour
what effect will a lesion to the medial/lateral hypothalamus have on weight?
medial lesion = obese
lateral lesion = lean
Due to effect on feeding beaviour
what 3 concepts underlie the concept of the feeding behaviour control system?
ssatiety and signalling
adiposity negative feedback signalling
food reward
what is satiety?
short term process regulating meal initiation and, termination and inter-meal frequency
what satiety signals increase during meals to limit the size?
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
what is the hunger signal and how does it work?
ghrelin (octanoregulated peptide)
produced and secreted by oxyntic cells in stomach
levels increase before and decrease after meal
stimulates food intake
how does the hypothalamus control obesity?
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
what are the 2 hormones involved in adiposity signalling and what is their function?
leptin
insulin
inform hypothalamus of fat status to alter energy balance (eat less and increase energy usage)
this is defective in obesity
what is the result of a leptin or leptin receptor deficiency?
uncontrollable obesity
what is leptin and what are its biological roles?
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
what are the functions of insulin?
central actions = inhibits food intake and decreases body weight in rodents
lack of receptor = obesity
adiposity signals = short term control
gut hormones = long term control, true or false?
false
other way around
what is “food reward”?
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
can leptin therapy help common obesity?
no
only those with rare genetic problem with leptin receptors due to leptin resistance
what is currently the only common over the counter drug for obesity and what are its side effects?
orlistat
side effects = cramping, severe diarrhoea, need for vitamin supplements
not very effective
name 4 potential anti-obesity drugs in the pipeline
lorcaserin
qsymia
contrive(mysimba)
liraglutide (saxenda)
how effective is bariatric surgery?
very
50-60% weight loss in 1 year
good resolution of type 2 diabetes
restricts calorie intake and induces malabsorption
what is adaptive thermogenesis?
induced browning of white adipose tissue as brown adipose tissue dissipates energy as heat via uncoupling protein 1 action
