Flashcards in Nutrition/ Diet 3 - Physiology of Feeding and Satiety Deck (51)
Physiological process whereby energy intake is matched to energy expenditure over time
What 2 factors cause obesity?
What are the 2 major factors that influence obesity
Accessible, tasty calorie dense food
What is metabolic syndrome (syndrome X)?
Central obesity plus 2 of:
Blood pressure greater than or equal to 130/85
Triglycerides greater than or equal to 1.7 mol/L
HDL less than 1.03 in males and 1.29 in females (mol/L)
Fasting glucose greater than or equal to 5.6mmol/L
Possible consequences of metabolic syndrome? (4)
More in list
What is the equation for BMI?
Wegith (kg) / square of height (m)
Categories of BMI?
Up to 25 = thin or normal
25-29.9 = overweight
30-39.9 = obese
greater than or equal to 40.0 = morbidly obese
What are some of the consequences of obesity (9)
Respiratory disease (sleep apnoea)
Heart disease (lipids, diabetes, hypertension)
NAFLD (fatty liver)
Cancer(Uterus, breast, prostate, colon)
Why do we need fat? (3)
Prevention of starvation
Energy buffer during prolonged illness
What is one of the reasons why it is difficult to lose weight?
Increased fat alters brain function in order that the brain views the fat as normal and dieting as a threat to body survival
How does the CNS influence energy balance and body weight (3)?
Behaviour - feeding and physical activity
ANS activity - regulates energy expenditure
Neuroendocrine system - secretion of hormones
(integration of these determines final output - feeding behaviour)
Where does the CNS influences on energy balance get integrated (in order to produce final behaviour)
How do we know this
In the hypothalamus in the brain
Lesioning ventromedial hypothalamus causes obesity
Lesioning lateral hypothalamus causes leaness
What 3 basic concepts underline the control system of energy intake and body weight?
Adiposity negative feedback signalling
What is satiation?
Sensation of fullness generated during a meal
What is satiety?
Period of time between termination of one meal and the initiation of the next
What is adiposity?
The state of being obese
What does the satiation and satiety processes regulate?
Meal intimation, termination and inter-meal frequency
When satiation signals increase
During meal to limit meal size
What are the satiation signals? (5)
Peptide YY (PYY3-36)
Glucagon-like peptide 1 (GLP-1)
Secreted from enteroendocrine cells in duodenum and jejunum
Released in proportion to lipids and proteins in meal
Signals via sensory nerves to hindbrain and stimulates hindbrain directly (Nucleus of solitary tract)
Peptide YY (PYY3-36)?
Secreted from endocrine mucosal L-cells of GI tract
Levels increase rapidly post-prandially
Inhibits gastric motility, slows emptying and reduces food intake (Hypo)
Glucagon-like peptide 1 (GLP-1)
Product of pro-glucagon gene
Also released from L cells in response to food ingestion
Inhibits gastric emptying reduces food intake (Hypo, NTS)
Also from pro-glucagon gene and released from oxyntic cells of small intestine after meal
Acts to suppress appetite - mechanism unclear
Peptide produced from gene that encodes gherkin and released from cells lining stomach/ small intestine
Suggested t reduce food intake - may act to antagonise the actions of gherkin - actions unclear at present
What is a hunger signal?
What is Gherkin?
Where is it produced and secreted?
How do its levels range?
Oxyntic cells in stomach
Levels increase before meals and decrease after meals
Levels are raised by fasting and hypoglycaemia
What does peripheral gherkin stimulate?
what does it decrease?
Food intake (hypo) and decreases fat utilisation
What doe gherkin-containing neurons in the hypothalamus do?
Help control fat metabolism, increasing lipogenesis (liver and adipose)
What do feedback loops which control overall energy balance do?
How does this work basically?
they act to maintain constancy of total body energy stores - why weight is stable in lean and obese individuals
Signals are produced in response to body nutritional status
These are sensed in the hypothalamus
These act to modulate food intake and energy expenditure
What central appetite controllers increase food intake when injected into the hypothalamic centres? (3)
(effects modest/ short lasting)