2: Physiology of feeding and satiety Flashcards
What is energy homeostasis?
Energy intake is matched to energy expenditure
How is excess energy stored?
Glycogen
Fat
What is the result of accessible junk food plus a sedentary lifestyle
i.e intake / expenditure mismatch?
Obesity
How is BMI calculated?
Weight (kg) / [Height (m)]2
Which BMI ranges correspond to the classifications:
Underweight
Normal
Overweight
Obese
Morbidly obese
< 18.0 ⇒ Underweight
18.0 - 24.9 ⇒ Normal
25.0 - 29.9 ⇒ Overweight
30.0 - 39.9 ⇒ Obese
> 40.0 ⇒ Morbidly obese
Levels of ___ have increased dramatically in the past 20 years.
obesity
Obesity increases your chances of early ___.
death
What are the two major factors influencing obesity?
Genetics - increases risk but not essential for disease expression
Environment - pushes people on to develop obesity
What is an endocrine condition associated with obesity?
Type 2 diabetes mellitus
What are some cardiovascular conditions associated with obesity?
Hypertension
MI
Stroke
During which situation is the energy stored by fat used?
Starvation
Infection (where you don’t feel like eating)
Increased body fat alters ___ function.
brain
Where is information regarding energy intake integrated?
Hypothalamus
What is satiation?
The feeling of “fullness” after a meal
What is satiety?
The period of time between one meal and the next
What are satiation signals?
Signals which control the feeling of “fullness”, i.e how much of a meal it feels right to eat
See binder for details on satiation signals.
Name a signal molecule which is released in response to fasting and hypoglycaemia?
Ghrelin
What is ghrelin?
What conditions is it released in response to?
Hunger signal
Released in response to fasting and hypoglycaemia
Ghrelin increases the magnitude of fat ___.
storage
Which type of feedback mechanism controls body weight and energy stores?
Negative feedback
Where is information re: body weight and energy storage integrated?
Hypothalamus
What are adiposity signals?
Hormones which report the fat status of the body to the hypothalamus
The levels of which two hormones increase as more fat is stored?
Leptin
Insulin
What do leptin and insulin instruct the brain to do?
Eat less
Increase energy expenditure
Patients with low leptin levels will have ___ appetites.
Why?
unrestrained - insatiable
Body thinks it is going through starvation as leptin reports level of energy storage
What hormone, other than leptin, acts as an adiposity signal?
Insulin
Which hormone is linked to food reward - the pleasure derived from eating?
Dopamine
People with high fat content will have high levels of circulating ___.
leptin
High circulating leptin levels associated with obesity cause receptors to become ___ to it.
insensitive
What is the only drug currently used in the treatment of obesity?
Orlistat (Alli)
How does orlistat reduce obesity?
Reduces fat absorption in the small intestine
What are the major side effects of orlistat (Alli)?
Cramps
Severe diarrhoea (+/- steatorrhoea)
What is bariatric surgery?
Surgery which aims to reduce the size of the stomach and therefore combat obesity
Name an example of bariatric surgery.
Gastric band
Gastric bypass
What effect does gastric bypass have on the excretion of satiation signals?
Reduced secretion of satiation signals
As there’s less stomach to do so
Which drug uncouples the proton gradient to cause weight loss by overheating?
2,4-dinitrophenol (DNP)
What is a major side effect of DNP?
Death by overheating
