Energy Balance and Nutrient Regulation

What does most of our food provide us with

energy and nutrients

what are nutrients

chemicals needed for growth, maintenance and repair of the body

what are the basic nutrients

carbohydrates, amino acids, lipids, vitamins and minerals

carbohydrates

glucose is the primary fuel of the body, all other carbs get converted to glucose

amino acids

come from proteins, basic building blocks for all cells

lipids (fats)

fats can be converted to free fatty acids as an alternate energy source

vitamins and minerals

do not provide calories - essential for digestion, cell building and maintaining homeostasis

glucose

sugar molecule which is ready energy

short term excess glucose

glycogen - stored in liver and muscles

glycogenesis

(glucose - glycogen) regulated by insulin

glycogenolysis

glycogen to glucose - regulated by glucagon

long term storage

lipids (Fats) stored in adipose tissue

gluconeogensis

converts fat and proteins to glucose and ketones

pancreas

regulates blood glucose levels through two hormones

glucagon

too little blood glucose (glycogenolysis)

insulin

too much blood glucose (glycogenesis)

what is the primary, backup and emergency fuel

glucose, fatty acids, gluconeogenesis

what is the percentage used by the body for digestion

33%

percentage used by the body for basal metabolism

55%

what is basal metabolism

heat production, maintenance of membrane potentials, and other life sustaining processes. Changes over lifespan

percentage of body used for active behavioral processes

12%

Can metabolism be adjusted

yes, in response to food intake, resisting weight loss or gain

what are the mechanisms that stimulate insulin release

cephalic phase, digestive/gastric phase, absorptive/substrate phase

cephalic phase (brain)

sight/smell/taste/thought of food trigger insulin release before food hits the gut

digestive or gastric phase (gut)

food entering the stomach and intestines causes them to release gut hormones, some stimulate the pancreas to release insulin

absorptive or substrate phase (blood/liver)

glucodetectors in blood and liver detect glucose and signal the pancreas to release insulin

diabetes mellitus

excess glucose levels secreted into urine making it sweet

type 1

autoimmune disorder leads to death of beta cells in pancreas = no insulin production

type 2 (adult onset)

reduced sensitivity to insulin, common associated with obesity

satiety

feeling that an appetite has been satisfied

what does the brain integrate to decide whether to initiate eating

insulin and glucose levels with other information

insulin as satiety signals

low insulin = hunger increases, increased food intake
moderate insulin = reduced food intake
very high insulin = glucose is driven out of bloodstream and stored as fat

glucose as satiety signals

untreated diabetes: high blood glucose but also increased hunger
blood glucose can remain stable for hours or days, while hunger still occurs

lateral hypothalamus

lesions cause aphagia (cessation of eating)

ventromedial hypothalamus

lesions cause animals to eat to excess and become obese