Reading Research Articles
Abstract
Purpose
Background/lit review summary
Study design
Experimental vs nonexperimental
Type?
Strength of study?
Methods
What stats methods used?
Methods sound?
n=
Population breakdown: age, gender, location, timeframe, etc.
Eligibility/exclusion criteria
What groups intervention group compared to?
Instrument validity?
Results
What were the findings?
Significant?
Strengths/weaknesses of study design
Are there similar comparable studies?
Implications for RD
Harris 2018 Systematic Review
Abstract
Purpose
Background/lit review summary
Study design
Experimental vs nonexperimental
Type?
Strength of study?
Methods
What stats methods used?
Methods sound?
n=
Population breakdown: age, gender, location, timeframe, etc.
Eligibility/exclusion criteria
What groups intervention group compared to?
Instrument validity?
Results
What were the findings?
Significant?
Strengths/weaknesses of study design
Are there similar comparable studies?
Implications for RD
Systematic Review
To examine the effectiveness of intermittent energy restriction in tx for OW/OB in adults, when compared to usual care tx or no tx.
Inclusion: BMI >/= 25kg/m2
age >/= 18
min 12 weeks
randomized/pseudo-randomized controlled trials
Exclusion:
6 studies
IEF = </= 800kcal 1-6days/wk
no tx (ad libitum)
usual care tx (~25% kcal restriction
Outcomes:
Primary: Change in BW
anthro. outcomes (BMI, waist circ, fat mass, fat-free mass
cardio-metabolic outcomes (blood glu, insulin, lipid panel, BP
Lifestyle (phys act., QOL, adverse events
Effect sizes: weighted mean differences
ADF, 5:2. up to 4d/wk
Age
Gender
Location
Timeframe
3-12 mo
4 compared to continuous kcal restriction, 2 no control
Typical of what we see IRL.
EIF > ad libidum
EIF ~ CR
Yes
IER > usual care - consistent
Str:
only used experimental/pseudo-experimental design, which are less likely to be biased than observational, etc.
Weak:
no sensitivity/subgroup analysis d/t small sample size
high attrition rates in studies reviewed
uncertain observer blinding in most studies
majority of studies are on female pts only
highlights need for studies on broader population
5-7% reduction in BW -> health benefits
-> studies seem to show it (not directly reported)
INTRO
importance of tx OB
-> % of adults w/ OW/OB, %OB
incr risk of DM2, CVA, etc.
many lifestyle interventions, little clinical impact
fad diets need to be reviewed
IF
types: 5:2,
ADF
IER 2-6d/wk
overall: normal kcal intake + short periods of severe calorie restriction/fasting
many studies are on animals
usual care: continuous energy restriction (CER)
600kcal/d restriction
need citation
Tinsley 2015
Abstract
Purpose: examine studies conducted on intermittent fasting programs to determine if they are effective at improving body composition and clinical health markers associated with disease
Background/lit review summary
Study design
Experimental vs nonexperimental
Type?
Strength of study?
Methods
What stats methods used?
Methods sound?
n=21
Population breakdown: age, gender, location, timeframe, etc.
Eligibility/exclusion criteria
What groups intervention group compared to?
Instrument validity?
Results
What were the findings?
Significant?
Strengths/weaknesses of study design
Are there similar comparable studies?
Implications for RD
time-restricted feeding
20:4 (isocaloric)
only 1 study reviewed
higher lipid panel except for TG
high attrition rate
meals were provided; likely that ppl would undereat calories if left to their own devices
16:8
no studies reviewed
most conservative: skip breakfast, don't eat after dinner
metabolic changes?
fasting periods 16h~1.5days
early fasting state (12-18h w/o food)
to
earlier stages of fasting state (18h-2d w/o food)
different outcomes for one-time short fast vs habitual short-term fasts
substrate use
v glu -> ^ FA w/i 24hr
see soeters et al
BG concentrations decline
lipolysis/b-oxidation incr
d/t reduced plasma insulin concentration, incr sympathetic nervous system activity, higher concentration of growth hormone?
need citation (see 38, 49 in references)
events **
(see klein et al)rate of FA incr greatest 12-24hr
account for 50-60% of total glycerol incr during 72hr fast
18-24hr - 50% incr in fat oxidation
50% decr glu oxidation
12-72hr - plasma insulin decr
(70% in 1st 24hr)
glucagon rises after 3 days
epinephrine/cortisol unchanged
but lipolytic response to epinephrine infusion incr @ 2-3d fasting?
benefit of this?
see klein et al
include significance of glucagon increase, metabolically
references listed on top left of p671
protein catabolism?
concern: protein breakdown, loss of lean body mass
observed, but mostly in overnight fast -> 60+ hr.
since duration of fasts is typically shorter, possible that protein breakdown not seen
citation 43 - urea nitrogen not incr at 36hr but incr at 60hr
soeters et al: ST ADF (20hfast-28hfeed) did not alter protein metabolism in lean healthy men
not many studies detailing how this is dif between NW vs OW/OB individuals
appears that protein catabolism incr @ 3rd day of fasting
at 2-3 days, energy mostly from glycogen breakdown / fat metabolism
see citation 30
resting metabolic rate
incr at 26-48hr?
so not really relevant here
discussion
IF programs are able to reduce BW/BF. - inconsistent
potential bias: publisher bias*
failure to report energy intake/energy expenditure
EF vs DCR
seem comparable, though results dif btwn indiv/btwn regimen
concerns
periods of semistarvation -> hyper plagic responses
-> incr fat mass
VLCD -> nutr deficiencies
-> electrolyte abnorm.
-> esp w/o medical supervision
sustainability/maintenance
->decr kcal -> promote wt gain after dieting? see citation 71
conc: advise appropriate supervision
no severe kcal restriction each day
review
not detailed
human clinical trials
M/F any age
study duration >3wk
n>10
complete/modified fasting
report BW/body composition
english
exclusion:
animal study
study <3wk
n<10
not english
religious fasting
ADF
whole-day fasting n-7
typical: alternate fasting w/ ad libitum days
fasting day = 1 meal at lunchtime, 25% EER
30-40hrs w/o food
modified fasting
-> really 2 separate fasting periods w/ small meal interruption
12-19hrs + 17-20hrs
Clinical markers
BW reduction, decr in fat mass
-> in normal->OB BMI ranges
fat-free mass: inconclusive
loss may be accelerated in ADF w/o modified fasting
lipid panel inconsistent
TChol, TG, LDL decr, in some studies
HDL mainly no change. incr maybe? and maybe only in women.
Some showed incr LDL
insulin resistance not observed or no change
*Most studies did not control for kcal intake
IF + kcal restriction
- modified fasting by lowering small amounts of food intake on fasting days
clinical markers
BW/Body fat: reductions
= Usual Care
no intervention