Pre-Midterm Content Flashcards
What is energy balance? When is it positive or negative?
energy balance = when energy that goes in matches the energy that goes out, weight should be maintained
positive = when you’re intaking more energy than you are expending, will gain weight
negative = when you’re intaking less energy than you are expending, will lose weight
What is RMR?
resting metabolic rate
how many calories you would burn if you laid in bed and did nothing all day
What is TEF?
thermogenic effect of food
energy of your body breaking down food
What is PAEE?
physical activity energy expenditure
Why might study data be misinterpreted by reporters or authors?
pressure to publish
publication bias (didn’t want to public “no results”)
pressure to achieve impact outside academic
misinterpretation by press/journalists
What are the 6 categories of nutrients?
carbohydrates fats proteins vitamins minerals water
What are the primary roles of nutrients?
provide energy
promote growth/development
regulate metabolism
What are the essential nutrients? What is left off this list?
water amino acids fatty acids minerals/trace minerals electrolytes vitamins
carbohydrates left off
What are the limitations of the Canadian Food Guide?
grains higher than they need to be
promotes fruits and veggies but not decreased consumption of starchy veggies
doesn’t promote decreased consumption of sugar, refined grains, processed meats, unhealthy oils, etc.
nothing about total calorie intake or energy balance
What are the 5 terms used to discuss nutrient content?
EAR - estimated average requirement RDA - recommended daily allowance AI - adequate intake UL - tolerable upper intake level DRI - daily reference intake
What is EAR?
estimated average requirement
amount of nutrient deemed sufficient to meet needs of the average individual in a certain age/gender group
minimum to not be deficient
at EAR, half of the specified group would NOT meet their nutritional needs
What is RDA?
recommended daily allowance
estimate of minimum daily average intake level meeting the nutrient requirements of nearly all healthy people (97-98%)
should be the goal for daily intake
RDA = EAR + 2 SD
What is AI?
used when sufficient evidence to estimate EAR is insignificant
goal for intake (since no RDAs can exist)
based on observed or experimentally determined value in healthy people
What is UL?
tolerable upper intake level
highest level likely to pose no risks of adverse health effects, any intake above will pose risks
need for this comes from supplementation
What is DRI?
dietary reference intake
umbrella term for group of reference values (EAR, RDA, AI, UL)
aimed at preventing/reducing disease incidence and promote optimal health
framework for new set of recommendations, can be used to plan/assess diets for healthy people
What is a kcal? How does it convert to kJ?
1 kcal (1 Cal) = energy to increase 1 kg of water by 1 degree celsius
1 kcal = 4.186 kJ
What are retrospective diet assessment techniques?
diet history/recall
- interviewer, food models
food frequency questionnaire
- amount, frequency
What are limitations of retrospective diet assessment techniques?
memory often inaccurate
alter habits/lie
judge portion sizes inaccurately
What are prospective diet assessment techniques?
duplicate meal
- make 2 copies of exact meal you would eat, eat one analyze the other
food records
- typically 3-7 days, use food consumption database
What are limitations of prospective diet assessment techniques?
cost/equipment
may still report inaccurately
database may lack foods
tend to underestimate intake by up to 20%
What are the functions of CHO?
major source of energy
forms important cell components
form smaller CHO compounds
What are the monosaccharides?
glucose (most common)
fructose (sweetest)
galactose (never alone)
What are the disaccharides?
sucrose
- honey, maple syrup
maltose
- fermentation
lactose
- milk
What are the types of complex CHO?
oligosaccharide (3-9 glucose)
polysaccharide (10+ glucose)
- short chains around 10-20 glucose
- starch/glycogen = thousands
What are the 2 arrangements of starch?
chain arrangement
- slow digestion
- ex. amylose
branched arrangement
- rapid digestion (easier to cleave parts off)
- ex. amylopectin
What is glycemic index?
numerical system that represents the rise in circulating blood sugar that 50g of CHO generates
higher = more blood sugar response
What are the classification levels of GI?
high GI = 70+
- ex. baked potatoes, ice cream
medium GI = 56-69
- ex. oatmeal, table sugar
low GI = 55 or less
- ex. eggs, apples
What is glycemic load?
impact of CHO consumption
considers both rate of entry of glucose into the blood and amount of CHO in the serving
(GI x g CHO per serving) / 100
What are the classification levels of GL?
high = 20+
medium = 11-19
low = 10 or less
What is glycogen?
thousands of branching glucose units
- branching to store the most
form of energy storage in animals, mainly in muscle and liver
What is dietary fibre? What is the recommended amount?
component of plans that resist digestive enzymes
increases satiety, slows absorption of glucose
recommended 25-38g/day
What are the 2 types of dietary fibre?
soluble
- soft fibres
- ex. oats, beans, figs
- controls blood glucose, reduces cholesterol
insoluble
- bulky fibres
- ex. cereals, apples
- prevents constipation and some cancers
What are normal blood glucose levels? What is the role of insulin?
4.4-5.5 mmol/L
insulin from the pancreas increases glucose uptake by the cells (to decrease blood glucose)
What is reactive/rebound hypoglycemia?
low blood sugar slightly after intake of high glycemic food
What are the average Western intakes of CHO?
40-60% of total energy intake
is this right? shouldn’t it have something to do with how active we are?
- yes
What is the minimum requirement for CHO?
130 g/day
What are the 3 types of fats?
triglycerides
cholesterol
phospholipids
What are the important roles of fat?
fuel during low-moderate/long-term exercise
essential FA
make things taste good
What are triglycerides?
main lipid in food and stored in the body
3 FFA and 1 glycerol backbone
- form an ester, go through esterification to remove H2O so weight doesn’t double
What is cholesterol?
many important roles:
- precursor of sex hormones/bile acids
- structural component of membranes
- TG transport in blood
found in animal products
HDL and LDL
What are phospholipids?
glycerol base, 1-2 FFA, phosphate group
found in many body tissues
similar to TG, can be made from TG!
- ingesting fats to make subsequent fasts also important
What are the 2 groups of FFA?
saturated
- solid at room temperature, packed tightly
- no double bonds
unsaturated
- liquid at room temperature, bends and kinks
- 1+ double bond (mono = 1, poly = multiple)
What is the smoking point of oils?
point at which heating changes chemical composition
denatures, produces potentially carcinogenic compounds
- decreases antioxidants and health benefits in general
What is hydrogenation?
adding H+ ions to saturate all of the unsaturated bonds
increase stability of food (can sit for long time)
alters texture (ex. pie crusts become flaky)
lose health benefits of unsaturated
- can also make trans fats
What are the 2 types of configurations of unsaturated FFA?
cis = normal
- H+ ions on same side of double bond
trans = created by commercially prepared foods
- H+ ions of opposite sides of double bond
- more difficult to digest, carcinogenic
What are the main functions of lipids?
structure of cell membranes
insulation/temperature regulation
protection/shock absorption
metabolism regulation
energy source
What are cell membranes made of?
phospholipids
affect permeability
heads are hydrophilic, face away from each other
tails are hydrophobic, face each other
How can fat work as insulation in different temperatures?
prevent too much heat loss in cold environments
provide protection from heat in warm environmnets
How can fat offer protection?
surrounds body’s organs
prevents organs from sinking due to downward stress of gravity
What compounds do fats create that regulate metabolism?
hormones
bile salts
blood clotting agents
eicosanoids (improve blood flow/vasodilation)
How can ketones act as an energy source?
when fasting or consuming high fat diets
accumulation can cause acidosis
- coma or death
What do we need to find the energy content of fat in reference to?
% energy content
not % mass
What are the recommended intake amounts for fat?
less than 30% total intake
- lower for obese/heart disease patients
about 1g/kg
of the 30%, mostly monounsaturated
What are Western intakes of fat? From what sources?
% have decreased but only because we are eating more in total
closer to 100-150g/day
95% intake from TG
1/3 from veggie 2/3 from animal
What makes up an amino acid?
C, O2, H+, N
amino group = distinguishing AA
R = organic side chain
more difficult to break down because we need to deaminate (break down N)
What are the functions of protein?
structure
- muscle, bone, hormones
metabolism regulation
energy (small amount)
What are peptide bonds?
join AA together
important to cleave for digestion
2 = dipeptide, 3 = tripeptide
50-100 = polypeptide
> 100 = protein
What are essential AA? What AA are considered essential?
AA that can’t be made, we must ingest them
histidine isoleucine leucine lysine methionine phenylalanine threonine tryptophan valine
Describe the pathway of protein.
taken in by intake of dietary protein or breaking down of tissues/hormone/enzymes/antibodies
can be synthesized into tissues/hormones/enzymes/antibodies or taken into the pool of AA in blood/fluids
from blood/fluids, is deaminated in liver where nitrogen can be excreted and carbon residue can be turned into CHO or FAT
What is a high quality protein?
complete protein that contains all EAA
good digestibility
usually from animal-derived foods
What is a low quality protein?
incomplete protein that lacks one or more AA
limiting EAA = one in short supply
usually from plant-derived foods
What are complementary PRO combinations?
incomplete protein sources that when eaten together provide a full complement of EAA
What are the health risks of a vegan diet?
low in zinc, iron, calcium, D, B12, riboflavin, etc.
higher intakes of phytates, oxalates, tannins that can bind to minerals and make them less available to the body
What is recommended PRO intake?
2.2 g/kg up to 6 months
gradually decreases to about 0.9 g/kg for 15-18 year olds
0.8 g/kg for healthy, inactive adults (may increase again for older adults)
What is the recommended PRO intake for athletes?
- 2-1.4 g/kg for endurance athletes
1. 6-1.8 g/kg for strength athletes
What are Western PRO intakes?
about 10-15%
well in excess
vegetarians at risk for marginal intake
Overall how have Western intake trends changed?
CHO increase
PRO =
FAT decrease
daily calories in total increase by about 200-300 more
What are the primary functions of the GI tract?
provide the body with nutrients, water, and electrolytes
perform digestion and absorption
What is digestion? Where does it occur?
chemical and mechanical breakdown of food into absorbable units
mouth, stomach, pancreas, gallbladder
What is absorption? Where does it occur?
movement of material from GI tract to ECF
small and large intestine
What is motility?
movement of material through GI tract as a result of muscle contraction
What is secretion?
movement of material from the cells into Gi tract
What is the GI tract?
long tube from mouth to anus
What functions occur at the mouth?
mechanical digestion through the teeth chewing (masticating)
salivary glands release fluid and digestive enzymes for chemical digestion
3 main functions:
- decrease food size and increase emptying
- increase food surface area
- mix food with saliva and enzymes
What functions occur at the esophagus/epiglottis?
tube from mouth to stomach
peristalsis
epiglottis = one-way door into esophagus, food can push past it but not back up
What functions occur at the stomach?
storage of large quantities of food
- normal volume 1.5 L but can expand to as much as 6.0L
mixing of food with acid to create chyme
- contacts and relaxes to help mix food with gastric juices (PRO digestion)
- 3rd layer of muscle is diagonal to push chyme downward
- regulation of emptying into intestines
highly acidic - thick stomach membrane to combat
What functions occur at the pancreas?
NaHCO3 and digestive enzymes break down PRO/CHO/FAT
What functions occur at the liver?
bile acids break down FAT
What functions occur at the gallbladder?
stores the bile from the liver
What functions occur in the small intestine?
digestion of food stuffs
absorption of water, nutrients, electrolytes
What functions occur in the large intestine?
reabsorption of water and electrolytes
stores feces at colon
What is peristalsis?
rhythmic contractions by ringed muscle of GI tract to push food from mouth to stomach
when rings contract, long muscles relax and tube constricts
when rings relax, long muscle tightens and tube bulges
What is responsible for mixing of food stuffs?
segmental contraction
some moves forward and mixes with what was pushed back by section ahead
What are the structural features of the small intestine?
3 sections
- duodenum
- jejunum
- ileum
2-3m in length, 3-5cm in diameter
folds greatly increase surface area for increased absorption
- folds, villi on folds, microvilli on villi
- total surface area may be 250m squared
lacteal = in villi, transport non-water soluble particles
What is the role of gastric juices?
PRO digestion
inactivate CHO enzymes with high acidity
acidity also prevents bacteria from growing/entering
What are the structural features of large intestine?
3 sections
- colon (ascending, transverse, descending)
- rectum
- anal canal
thicker membrane, less absorption
How is the GI tract regulated by the nervous system?
parasympathetic stimulates motility
sympathetic diverts blood flow to muscles, impairs digestion/absorption
sensory neurons within GI tract intrinsically control
hormones secreted affect secretion/motility
What are the 2 main GI hormones?
gastrin
- secreted by stomach
- stimulates HCl production and pepsinogen secretion in stomach
- mucosal growth
secretin
- secreted in small intestine
- stimulates water and bicarbonate secretion in pancreatic juice (neutralizes chyme to avoid small intestine damage)
How much time does food spend in the GI tract?
1-3 days
0.5-2cm/sec
not very fast considering length of system
How does saliva secretion change when stimulated?
unstimulated = 0.5mL
stimulated = 10 fold higher
excited by the food you are going to eat
What are the contents of saliva?
99.5% water to moisten food
alpha amylase
- break down starch
mucoid proteins increase alpha amylase function
protein antibodies
electrolytes, bicarbonate, lysozymes, enzymes, lingual lipase
Describe the digestion of CHO.
mechanical and chemical breakdown in mouth
once food is swallowed and digested, arrive in the stomach where acids decrease amylase function, digestion slows
- 30-40% digested before it gets there
CHO emptied into SI
acid neutralized, additional amylase added with pancreatic juice to increase digestion rate again
most starches hydrolyzed before ileum (break bonds with water)
brush border contains lactase, sucrase, maltase to breakdown disaccharides into monosaccharides for absorption
How is fibre digested?
fibre contains cellulose which is resistant to human digestive enzymes - we can’t break it down
cellulose excreted in feces or fermented (gas)
slow motility allows for more time for digestion/breakdown of what we can digest
How is CHO absorbed? (3 mechanisms)
simple sugars use different transport mechanisms
from SI to membrane:
- sodium-glucose linked transporter
- Na+ dependent transporter for glucose and galactose (for each molecule to membrane, 2 Na+ ions goes into gut lumen - recycled) - GLUT5
- facilitated diffusion transporter for fructose
from membrane to capillary/circulation:
- GLUT2
- accepts all 3 simple sugars to distribute around the body
Where does fat digestion begin?
in the mouth with lingual lipase
- splits TG into 2 FA and a monoglycerol
- not affected by acidity, so digestion continues; completes 10-30% of all TG digestion
Why is the fat digestion process slow?
TG insolubility
don’t mix well with water fraction of lipase
chyme contains large fat droplets needed to increase surface area
Summarize fat digestion.
TGs broken into FFA and monoglyercol by lingual lipase
when chyme enters SI, still full of large lipid droplets
- bile added
- fats insolubility in water requires bile (hydrophilic component to interact with water, hydrophobic component to interact with lipid)
- creates stable emulsion (smaller lipid droplets) that allows lipases to work, digestion picks up
pancreas releases lipase to further break down fat
- allows access of fats inside bile coating
components reformed and absorbed into villi via micelles
Summarize fat absorption for LCFA (most common).
1st packaging
- LCFAs incorporated into micelles, ferried to enterocyte
- contents break out once across
2nd packaging
- monoglycerols and FA move to endoplasmic reticulum and recombine into TGs
- TGs join with cholesterol and protein to form large chylomicrons (can’t directly cross into blood)
MAJOR EXTRA STEP IN FAT DIGESTION
- chylomicrons must be packaged into secretory vesicles and removed via exocytosis into lacteals
- go through lymphatic system, eventually enter bloodstream at thoracic duct
Summarize fat absorption for SCFA/MCFA.
don’t require micelles
more soluble in water, can bind to albumin in blood and directly cross the membrane to enter the bloodstream
What is the main purpose of chylomicrons?
transport fat into blood
What is HDL and LDL?
cholesterol types
high-density lipoprotein (apoprotein A)
- healthy
- high protein, low cholesterol
low-density lipoprotein (apoprotein B)
- unhealthy
- low protein, high cholesterol
Once in the bloodstream, what happens to chylomicrons?
FFA transported into fat or muscle
glycerol and rest of chylomicron transported to liver, recombined into other components
- ex. phospholipid, cholesterol, TG, protein
When does PRO digestion begin?
in the stomach (minus mastication)
stomach acid activates proteases that breakdown food proteins into polypeptides then AA
How is PRO digested differently based on type?
unequal
plant PRO least digestible
egg PRO is highest (90%+)
What are the 2 types of PRO digestion enzymes?
endopeptidase/protease
- attack interior bonds
- cleave PRO into smaller units
- major work
exopeptidase
- work from ends
- cleave off individual AA in sequence
result in AA, dipeptides, and tripeptides
Once proteases activated by stomach acid, what happens in PRO digestion?
acid neutralized by bicarbonate in SI
- from pancreatic juice
ready for absorption
How can AA transport mechanisms be saturated?
if you eat a lot of a specific AA, may block absorption of another
shares transporters
Describe PRO absorption.
- into enterocyte:
most free AA absorbed via Na+ dependent transport
dipeptides and tripeptides use PepT1 (H+ dependent)
- broken down into AA once inside enterocyte
- into blood:
AA absorbed into blood via Na+ dependent transport
- then travel to liver to be converted or released back into blood as free AAs
Where is water absorbed? How is it absorbed?
- 5% in SI
- 72% in duodenum
entirely by simple diffusion/laws of osmosis
How are ions absorbed?
Na+ through 3 membrane proteins
- Na+ channels
- Na+-Cl- symporter
- Na+-H+ exchanger
once inside enterocytem Na+-K+ pump is primary transporter
K+ moves by paracellular pathway (passing through intracellular space between cells)
How are vitamins absorbed?
fat soluble vitamins absorbed in SI with FFA
- A, D, E, K
How are minerals absorbed?
not well, usually require active transport and still have absorption rates far less than 50%
absorption can increase when intake is low
What is the role of bacteria? Where is it mostly found?
feed on undigested nutrients
- fermentation of cellulose
produces vitamins/minerals, important for blood clotting, brain/NS function, metabolism
found most in SI
- stomach acidity too high for bacteria to survive
What is the difference between a prebiotic and a probiotic?
probiotic
- bacteria that you eat
- promote gut and immune health
prebiotics
- stimulate growth of good bacteria in the bowel
- found in wheat, oats, garlic, some veggies
both have widespread health benefits
What factors affect digestion regulation?
food
- sight, smell, thought
drink
- volume, energy density
temperature
- of food/drink and of body
exercise
- type and intensity
stress/anxiety
gender
What is the enteric nerve plexus?
“little brain” in the gut wall
- direct communication from gut to other organs in regulating motility/secretion
- integrates sensory info from GI tract and initiates a response
What are long reflexes outside and inside the GI?
afferent info to CNS
outside GI = feedforward from brain
- smell, sight, thought
inside GI = from GI tract
- PNS via vagus nerve excitatory
- SNS is inhibitory
What is the stimulus for release and primary effects of gastric inhibitory peptide?
stimulus:
- glucose, FA, AA (in SI)
- inhibited by eating a meal
effects:
- stimulates insulin release
- inhibits gastric emptying and acid secretion
What is the stimulus for release and primary effects of cholecystokin?
stimulus:
- fatty acids, some AA
effect:
- satiety hormone; more food = more CCK = less hungry
- stimulates gallbladder contraction and pancreatic secretion
- inhibits gastric emptying and acid secretion
What is the stimulus for release and primary effects of glucagon-like peptide 1?
stimulus:
- mixed meal that includes CHO/FAT
effect:
- stimulates insulin release, promotes satiety
- inhibits glucagon release and gastric functioning
What are 3 categories of GI problems with exercise?
physiological
- decrease blood flow (redirected to muscle)
- cramps
mechanical
- posture/impact
nutritional
- dehydration
- distress (dairy, concentrated beverages)
What are some GI issues in upper and lower GI tract?
upper
- heartburn, bloating, vomiting
lower
- urge to defecate, diarrhea
What are things to avoid to prevent GI issues?
- trying new things on day of performance
- dairy
- fibre
- aspirin
- high fructose
- dehydration
What factors determine fuel use and fatigue?
exercise intensity and duration
FITT principle
What is direct calorimetry?
food combusted in chamber
heat produced = energy content of the food
What is the available content of CHO, FAT, and PRO due to inefficiency?
1g CHO = 4 kcal
1g FAT = 9 kcal
1g PRO = 4 kcal
the gross energy content is not completely absorbed
What is the Atwater Correction Factor?
godfather of energy balance
corrections in kcal/g of nutrients to account for differences in absorption
What are coefficients of digestibility?
tell us how well our body can process something
easily digest CHO/FAT
animal PRO absorbed better than plant PRO
What are the components of energy expenditure?
60% RMR
32% physical activity
8% TEF
What is BMR?
basal metabolic rate
your body sustaining life, never getting up
RMR slightly higher
What is a person’s average RMR?
1 kcal/kg/h
depends on muscle mass, age, gender, fitness, weight loss, hormones, etc.
Describe characteristics of TEF.
increase due to digestion/absorption following food intake
1-4 hours following a meal = 8-10% increase in RMR
magnitude depends on types of food taken in (CHO and PRO > FAT)
differs from lean and obese individuals
How does TDEE change between sedentary and very active individuals?
sedentary
- vast majority RMR
- some TEE
very active
- majority TEE
- some RMR
both about equal parts TEF/DIT
What is the Harris Benedict Equation for?
calculate BMR and daily kcal requirements
What is the static view of energy balance? What is it actually like?
RMR/PA balance with food intake
not as simple, many things influence
What is SPA?
not explicitly exercising
ex. walking up the stairs to class
Why are obesity rates increasing?
portion sizes increase
increase in sedentary behaviours
increased access to junk food
Why is BMI not an appropriate gage of healthy weight?
doesn’t account for composition
ex. 200 lbs of muscle vs. 200 lbs of fat
What is waist:hip ratios?
female > 0.85, gynoid/pear
male > 0.95, apple/android
if higher, higher risk for chronic disease
narrowest point = waist, widest = hips
What are skin folds?
relationship between subcutaneous and total fat
not advisable on obese individuals, more error
7-10 sites recommended
What are the 2, 3, and 4 compartment models of body composition?
2
- fat vs fat free mass
- ex. skin folds
3
- fat mass, lean mass, water
4
- water, bone, lean mass, fat mass
- ex. DXA
What is BIA?
bioelectric impedance analysis
“barefoot scales”
electrodes placed on body, current is applied, greater resistance = greater fat
different tissues/substances have different signal resistances (ex. fat will impede, muscle will speed up signal)
What is densitometry?
density = mass/volume
differences in density between fat and fat-free mass
measure mass, then measure volume through either hydrostatic weighing or air displacement
use to determine density
What is DXA?
dual energy x-ray absorptiometry
lay on table, X-rays put through you and measure how distorted it is from source to receiver
- different tissues absorb differently
What is CT?
computed tomography
use ionized radiation by x-ray (large dose, not feasible for whole body)
transverse views of body segments
What is pQCT?
can examine bone strength/shape, patterns of subcutaneous fat, etc in older adults
What is MRI?
use strong magnetic fields and radio-waves
accurately quantify muscle size
What is the Atkins diet? Issues?
lose weight by drastically cutting back CHO
- low CHO, high FAT
uses ketones
- works in the short term, not sustainable
- blames CHO for obesity
What is the Bernstein diet? Issues?
very low calorie as well as low CHO
constant visits, Vitamin B shots
- works in short term, not sustainable
- “medically backed 20 lbs loss per month”
- extremely restrictive
What is the Mediterranean diet? Issues?
lots of heart healthy fats
seafood, nuts, legumes, fruits, veggies, red wine, olive oil
everything in moderation
more of a lifestyle change than a weight loss plan
- positive in health but not a lot of data on body composition
- bit low in calcium (lack of dairy)
- can be expensive
What is the Paleo diet? Issues?
eat like our ancestors
fish, meat, eggs, fruits/veggies
no grains, dairy, sugars, oils, legumes/starchy veggies, processed foods
emphasis on exercise, high protein, no calorie restrictions
- extremely hard to do
- not sustainable
What is the Slow CHO diet? Issues?
eat foods low in glycemic index
eliminate starches, sweets, dairy, fruit
main foods are eggs, meat, lentils, nuts, legumes, veggies
emphasize fermented foods
1 cheat day (good for sustainability)
- no evidence that it works aside from short term
- proposes 20 lbs/month (red flag)
What is the South Beach diet? Issues?
control hunger by eating before it strikes
low CHO, high PRO
focus on lean PRO, low fat dairy, good CHO (fruits/veggies, whole grains)
phases: 1st strict, 3rd maintenance
- no evidence that it works
- works short term, mediocre sustainability
What is Weight Watchers diet?
flexible, eat a balanced diet, in moderation, eat what you want
uses a point system to track what you eat
local meetings with motivation and weigh-ins
1st commercialized weight loss program to do clinical trials
effective, relatively
What is the Zone diet? Issues?
equal, balanced
40% CHO, 30% FAT, 30% PRO
but 1000-1300 kcal/day
proper hormone balance
- extremely calorically restrictive
- works short term, mediocre sustainability
What are the types of intermittent fasting?
alternate day
- 36h fast, 12h feed
modified
- fasting days = extreme caloric restriction (25% needs)
time-restricted
- free feeding within certain windows
- ex. 16h fast 8h feed, 20h fast 4h feed
What are ketogenic diets? Issues?
little to no CHO intake
body relies on fat producing ketones for energy
can be deadly if going into ketoacidosis
often associated with large caloric restriction
hard to say where weight loss comes from
- may be largely fat-free mass
What are similarities between all the diets?
most use “medical backing” as evidence
most are for commercial gain
most work in the short-term
most are restrictive/low-calorie, are not lifestyle
rapid weight loss which could be unhealthy
Study: Endurance cyclists ate either high fat or high CHO diets (isoenergetic) and did a DXA for body composition.
body composition remained unchanged
high fat does not mean fat gain
energy balance is key factor
Study: Obese subjects consumed either LCHF or LFHC diets (isoenergetic and hypocaloric, equal PRO) and measured weight/composition changes.
weight loss, fat loss, waist circumference all changed equally
in calorie drought, energy balance matters regardless of source
Study: Obese subjects consumed either LPHC or LCHP diets that were isoenergetic and slightly hypocaloric and measured weight loss and RMR.
high PRO lost more weight
high CHO decreased RMR
majority of weight loss was water since loss of CHO and water stored with it
- weight loss doesn’t equal fat loss
Study: Obese studies consumed either LPHC or LCHP diets ad libitum, measured weight/fat loss and eating patterns.
high PRO lose more weight and fat
- LCHP diet promotes negative energy balance
high CHO lost for first 3 months and then had plateau, where PRO group continued
high PRO group ate less food (more satiated)
- CHO less satisfying
What can override satiety?
taste/smell of food
time of day/memory
social situations
stress
Study: Women ate isoenergetic, 30% FAT diets with either high CHO or high PRO, either sedentary or exercising. Measured weight/fat loss.
high PRO group lost most weight and fat mass as well as least lean mass
exercise and PRO had independent and additive effects
LCHP diet plus exercise is superior strategy
Study: Young, overweight males were provided meals that were 40% hypoenergetic, one group ate 1.2g/kg PRO and other ate 2.4g/kg PRO with intense 6d/week exercise regime. Measured weight and fat loss.
high PRO group lost more weight, almost entirely fat
lean mass increased
What is the role of blood insulin?
increase fat storage and decrease fat use
poor for weight loss
low insulin = increased fat mobilization and decreased storage
Study: What happened to chip intake when when no nutrition information was given versus when is was given?
not given:
- no difference between dieting and non-dieting in chip intake
given:
- not dieting ate similar amount
- dieting ate MORE fat-free chips (same kcal)
increased intake when foods are marked low-fat/fat-free, however many of these foods are high in CHO still
What happens to EE when EI is restricted?
EE decreases
body is attempting to preserve mass, prevent fatigue
Study: People ate extremely energy-restricted diets, either high PRO, CHO or FAT
decrease in RMR was the least in high PRO group
- greater TEF
dietary PRO maintains RMR
What are the effects of high PRO intake?
lower insulin = increased fat mobilization and decreased storage
protein sparing effect on lean mass
higher satiety = decreased EI
increased RMR + energy expenditure in aerobic exercise
- increased TDEE
What is orexigenic? What is anorexigenic?
orexigenic = appetite stimulation
- ghrelin
anorexigenic = satiety stimulation
- PYY, GLP1, PP, leptin
What is the arcuate nucleus role in hunger?
ARC region in hypothalamus
generates release of neuropeptides which travel across brain to excite/inhibit activity
What is special about leptin?
only tonic hormone
chronic indicator of energy balance
others are short-term, meal to meal variance
How does energy balance differ with endurance training versus interval training?
endurance training burns more calories
interval training lost more fat in way less time exercising
EPOC may make energy expenditure higher over 24h
- may decreases hunger after exercise
What is the difference between HIIT and SIT?
HIIT = intervals up to maximal
SIT = intervals above maximal
What is the energy value of alcohol?
7 kcal/g
lots of calories from fat
What does the body have to do to process alcohol?
alcohol can’t be stored
alcohol -> acetylaldehyde -> acetic acid -> acetate
acetate is stored as fat
reaction requires NADH, with in excess prevents making glucose and results in hypoglycemia
What causes hangovers?
alcohol over 4%
- prevents ADH release
- excessive urination
- dehydration and loss of water soluble vitamins
How does alcohol promote fat formation/storage?
excess energy causes insulin to stimulate TG storage, causing generation of FA and TG
prevents fat oxidation
What is considered safe/sustainable weight loss?
1% weight loss per week/about 1-2 pounds
caloric deficit of 500-1000 calories per day
intense restriction = rapid weight loss but not of fat, mostly glycogen in water, in some cases even PRO
What are some effective weight loss strategies?
multiple smaller meals to stimulate metabolic rate
- eat every 2-3 hours, decreases hunger and EI
PRO with every intake
- increases satiety, slows absorption
low glycemic load CHO
- reduce insulin
What results from common dieting trends of caloric restriction or cutting stuff out?
increased appetite
decreased energy expenditure during PA
decreased RMR
altered hormonal profile
How can we use our hands to measure portion sizes?
fist = 1 serving veggies
palm = 1 serving protein
cupped hand = 1 serving CHO
thumb = 1 serving fat
