Lecture 22 - Food Intake and Disordered Eating Part I

cachexia

a condition of physical wasting away due to the loss of weight and muscle mass that occurs even with calories

happens in patients with diseases such as tuberculosis, HIV/AIDS, Cancer

Sarcopenia

condition characterized by loss of muscle mass and muscle strength

- age related

- cachexia

- disuse (immobility, physical inability, zero gravity)

- endocrine

- neurodegenerative disease

- starvation malabsorption

normal response to infection

- changes in trace elements, anemia

- fever

- loss of appetite

- sleep, lethargy

- failures of ketosis with starvation

- nitrogen loss

results of refeeding a starving person with infection

- exclusively fat gained! no lean body mass

can grandma’s nutritional state affect you?

grandma’s nutritional state affect my physiology (independent of the nutritional state of your mother)

hunger vs appetite

hunger: the physical feeling you experience when your body needs energy

appetite: the desire to eat, triggered by cravings, habits, the availability of food, other social and emotional factors

peripheral tissue regulation of hunger and satiety

signals originates from

- GI tract: recent food intake

- Pancreas: energy recevies

- adipose tissue: energy reserves

signals go to the hypothalamus and act via neuropeptide

What are these signals?

- nerves, hormones

- signals before and after food intake

- signal about amount of food consumed, availability of certain nutrients

short-term regulation of food intake

gastric stretching - stretch receptors

circulating nutrient content

GI hormones:

- ghrelin (made in stomach), causes hunger, decreases after meal; levels high when body is in negative energy balance

- cck and peptide YY: made in small intestine, stimulated by presence of protein and fatty acids, signals brain to decrease food intake

long-term regulation of food intake

signals energy reserves to brain

- insulin (also short term)

- leptin: hormone produced by adipose tissue

- when we make more fat, more leptin is produced, and when we make less fat tissue, less leptin is produced

parabiosis study

surgical joining of two living organisms in such a way that they develop a single, shared physiological system

Leptin

signals hypothalamus

- alters feeding behavior and hunger

- body temperature

- energy regulation

- product of ob gene

deficiency: obesity

low insulin + low leptin

signals to brain: body has low glucose, low fat stores

increase food intake and decrease energy expenditure

high insulin + high leptin

signals to brain: body has high glucose:, low fat stores

decrease food intake and increase energy expenditure

recombinant leptin injections

decreased: fat mass, food intake, hyperlipidemia, lipid levels, weight

improved: immune function, thyroid function

neurochemical systems underlying reward (food) in brain

1) a learning system that involves knowledge about the reward

2) homeostasis in energy balance

3) a hedonic "want" or "desire" system