Loading presentation...

Present Remotely

Send the link below via email or IM

Copy

Present to your audience

Start remote presentation

  • Invited audience members will follow you as you navigate and present
  • People invited to a presentation do not need a Prezi account
  • This link expires 10 minutes after you close the presentation
  • A maximum of 30 users can follow your presentation
  • Learn more about this feature in our knowledge base article

Do you really want to delete this prezi?

Neither you, nor the coeditors you shared it with will be able to recover it again.

DeleteCancel

Make your likes visible on Facebook?

Connect your Facebook account to Prezi and let your likes appear on your timeline.
You can change this under Settings & Account at any time.

No, thanks

Mind the Gap

Project development
by

DJ Hume

on 6 December 2015

Comments (0)

Please log in to add your comment.

Report abuse

Transcript of Mind the Gap

MIND THE GAP
INVESTIGATING WEIGHT LOSS RELAPSE
BEHAVIOUR
PERCEPTION
THE ENERGY GAP
Difference in energy intake & energy expenditure which must be sustained to:
1. Prevent further weight gain (primary prevention),
2. Achieve SUSTAINABLE weight loss.

SO THEN WHY AREN'T WE ALL SKINNY?
"Body weight is HOMEOSTATIC, and a REGULATORY SYSTEM will readily defend impositions that
promote a negative energy balance" - N. KING [2007]

A FEW STATISTICS:
50-80% OF FORMERLY OVERWEIGHT/OBESE INDIVIDUALS RETURN TO STARTING WEIGHT WITHIN 3-5 YRS AFTER INITIAL TREATMENT
A series of
COMPENSATORY RESPONSES
to a
significant reduction in body weight render subsequent weight loss maintenance improbable
These responses can be classified as:

Autonomic Compensatory Responses (ACRs):
cannot be willingly or selectively altered

Volitional Compensatory Responses (VCRs):
allow for degrees of choice and cognitive self-control
HUNGER HORMONES
METABOLIC RATE
POSTPRANDIAL CHANGES
ENDOCRINE SYSTEM
DEPOT-SPECIFIC FAT DISTRIBUTION
NEURAL ACTIVATION
SUBSTRATE OXIDATION
Gut: incr. appetite-stimulating hormone GHRELIN
Adipose tissue: decr. appetite-suppressing hormone LEPTIN
Decr. sleeping & resting met. rate
Incr. energy conservation capacity of skeletal muscle
Decr. thermic effect of feeding
Incr. fractional energy absorption
throughout GIT
Decr. insulin sensitivity
Decr. oxidative enzyme capacity
Decr. hormone-sensitive lipase activity
Incr. intramuscular lipid deposition
Incr. Visceral Adipose Tissue
Altered Sympathetic NS
Function
7 primary categories of ACRS
which have "ENERGY-SPARING" effects
ACRS or VCRS?
E.g. an incr. in food intake could be driven
biologically
(change in hunger hormone activity) or
psychologically
(a motivation to reward oneself for exercise adherence)
DIETARY BEHAVIOURS
EXERCISE BEHAVIOURS
SLEEP
preference for energy dense (high sugar, high fat) foods

frequent episodes of disinhibition caused by restrained eating

increase in portion size

Increase in eating frequency (e.g. snacking between meals)
reductions in non-exercise activity thermogenesis or “NEAT” (an ACR)

reductions in premeditated activity-related thermogenesis (a VCR)
Autonomic disruptions in sleep quality & quantity: hunger hormones are affected, providing further encouragement for a + energy balance
REDUCED WEIGHT
MOST IMPORTANT
VARIABLES FOR GROUP DEF:
WHO DO WE INVESTIGATE?
PHENOTYPE
WEIGHT HISTORY
GROUPS
Starting BMI of
27-39
Total reduction of
15%+
Maintained current BMI
12mo+
ALWAYS LEAN
Always had a BMI of
27-
VS
INCLUSION CRITERIA
Women aged 21 - 45
Remained weight stable for the past 3 months (no positive or negative weight fluctuations of more than 5% of current weight)

EXCLUSION CRITERIA
Menopause, pregnancy, lactation
A weight reduction of more than 5% among lean or obese CONTROL candidates at any point in their lifespan
THE EXPERIMENTAL PROCEDURES
Clinical Trial 2
EEG Test
1
2
3
Clinical Trial 1
Anthro &
Body Comp
Oral Glucose Tolerance Test
RMR Familiarization
Height & Weight
Waist, hip, upper and lower limb circumferences
Humeral and femoral bone breadths
Sum of 7 skin folds
Bioelectrical Impedance Analysis
VENTILATED HOOD TECHNIQUE
RHR and RBP
0 min
Submaximal
Treadmill Test
4 min @ 50-70% APMHR
4 min @ same speed + 5% incline
2 min HR recovery
DURATION: 3-3.5 hours
True
RMR
20 minutes
Fasting Bloods
DURATION: 4.5-5 hours
5 x 9ml (insulin & lipids)
2 x 6ml (hunger hormones)
1 x 4ml (glucose)
High Fat Liquid Meal
100ml full cream milk
200ml cream
200g full fat ice cream
1130 kCal
20 minutes
20 minutes
20 minutes
20 minutes
RMR
00:05-00:25
RMR
RMR
RMR
01:05-01:25
02:05-02:25
03:05-03:25
01:00
Bloods (2 x 6ml)
Satiety (VAS)
02:00
Bloods (2 x 6ml)
Satiety (VAS)
03:00
Bloods (2 x 6ml)
Satiety (VAS)
Post Test Meal
PRE
VAS

Meal
weight
POST
VAS

Meal
weight
04:00
137 kCal/100g
412 kCal/300g serv.
Pre and Post
Satiety VAS
10min to consume
THERMIC EFFECT OF FOOD
HUNGER HORMONE RESPONSE (LEPTIN & GHRELIN)
Satiety
(VAS)
Stroop
Practise Task
Instructed to stop
eating 2-4 hrs prior
DURATION: 1 hour
INFORMED
RED
BLUE
GREEN
YELLOW
BLUE
Office Task
RED
BLUE
GREEN
YELLOW
BLUE
Food Task
RED
BLUE
GREEN
YELLOW
BLUE
Setup
PHYSIOLOGICAL DOMAIN
PSYCHO-BEHAVIOURAL DOMAIN
PERCEPTUAL DOMAIN
HYPOTHESES
OUTCOME
VARIABLES

Body composition
Somatotype
Prevalence of IFG and hypertension
Predicted VO2max
Metabolic rate and substrate oxidation (metabolic flexibility) at rest & after a high-fat meal
Plasma glucose, insulin, FFA, ghrelin, leptin, orexin-A
Breathing and Heart Rate Variability
Total daily energy intake
Diet macronutrient composition
Habitual fat intake
Appetite and satiety
Body shape awareness
Cognitive eating restraint, disinhibition & hunger
Weight and exercise self-efficacy
Depression
Sleep quality and quantity
Personality Type
Pre-conscious & conscious food processing
Objective vs subjective PA
Objective vs subjective food portion sizes
WEIGHT LOSS MAINTAINERS and ALWAYS LEAN CONTROLS will be indistinguishable with regard to
PHYSIOLOGY

but MAINTAINERS will demonstrate

EATING/EXERCISE BEHAVIOURS

which sustain weight loss.

WEIGHT REGAINERS and ALWAYS OBESE CONTROLS
will be indistinguishable with regard to
EATING/EXERCISE BEHAVIOURS

but REGAINERS will demonstrate

PERCEPTUAL CHANGES

which lapse weight loss maintenance.
Causes of Obesity
Research Aim
Genetics
Overeating
Overconsumption of Simple carbohydrates
Slow metabolism
Physical inactivity
Medications
Depression
Metabolic inflexibility
Environment
Stress
Boredom
Endocrine dysfunction
Eating disorders
Insufficient sleep
Smoking cessation
Self efficacy
Autonomic nervous system dysfunction
illness
Reproductive history
Limited knowledge of health behaviours
Arousal in response to food cues
SES
Menses
Early life experiences
Investigate the differences in:
Physiological markers
and metabolic profile
Between 4 groups of women:
Psycho-behavioural
characteristics
Perception of
food & physical activity
LEAN
REDUCED
OBESE
RELAPSED
Which variables primarily drive
these phenotypes?
WEIGHT HX
MEDICAL HX (SELF & FAMILY)
MEDICATIONS & CARDIAC RISK FACTORS
ORTHOPAEDIC RISK FACTORS
3 FACTOR EATING Q
SHORT FAT Q
BRUNEL PHYSICAL ACTIVITY Q
GLOBAL PHYSICAL ACTIVITY Q

BODY SHAPE & BODY IMAGE
GENERAL & WEIGHT SELF EFFICACY
BECK DEPRESSION INVENTORY
MYER'S-BRIGGS TYPE INDICATOR
PITTSBURGH SLEEP QUALITY INDEX
Estimated VO2max (in mL • kg-1 • min-1) = 15.1 + (21.8 x speed in mph) - (0.327 x SS HR in bpm) - (0.263 x speed x age in years) + (0.00504 x SS HR in bpm x age in years) + (5.98 x gender: female = 0, male = 1)
GT3X ACCELEROMETER
CHOICE
NO CHOICE
Reduced Overweight OR Reduced Obese
RELAPSED
Starting BMI of
27-39
Total reduction of
15%+
Regained entire
15% (or more)
ALWAYS O.Wt/OBESE
Always had a BMI of
27+
VS
Relapsed Overweight OR Relapsed Obese
[BMI MATCHED GROUPS]
[BMI MATCHED GROUPS]
20 - 25 minutes
ASA24
FOOD PORTION SIZE EVALUATION
Observations from data
quality checks...
Prelim. Data
From Visit 1
From Visit 2
From Visit 3
Failure of RQ-lowering in response to a high-fat stimulus
Incr. RQ in fasted state
Elevated RQ response to 10-h fast in metabolically Inflexible subjects
[Galgani, Moro & Ravussin, Am J
Physiol Endocrinol Metab, 2008.]
30 min
60 min
90 min
120 min
Eating and Exercise Behaviours
General Health
(current and past)
SES & Demographics
Psychology & Sleep
Screening
Questionnaires
GENERAL HEALTH SURVEY
BASIC HEALTH HABITS
REPRODUCTIVE HX
HIV STATUS
EDUCATION
OCCUPATION
INCOME
LIVING ARRANGEMENTS
BASIC ASSETS
Ebbeling Equation
EBBELING ET AL. 1991
7 DAYS
CONSENT
A
utomated
S
elf
A
dministered
24
-hr Recall
P300 Window:

Conscious [maintained] attentional processing stimulus evaluation and categorization, decision making,
motivation and drive (more executive)
WHAT IS EEG?
EEG (
Electroencephalography
):
Recording of the brain's spontaneous
electrical activity, as sourced from the
scalp's surface over time
ERPs (
Event-related Potentials
): averaged EEG responses to sensory stilumli
The cerebral cortex is formed of small "cylinders" containing "vertical chains" of neurons
Each cylinder is about 50 microns in diameter
EEG detects postsynaptic action potentials in these cylinders i.e. excitatory and inhibitory responses from
SYNCHRONIZED
cortical neurons (not activity from individual cells)
Specifically, EEG recognizes voltages transferred along
apical dendrites
of pyramidal cells
MORE ABOUT THE PHYSIOLOGICAL
PROCESS DETECTED BY EEG:
apical
dendrite
soma
50 microns
GOAL: Detect high resolution (millisecond)
changes in brain activity associated with
various levels of information processing
"executive"
P200 Window:
Automatic
pre-conscious
attentional processing: visual cognition
cognitive matching system comparing
visual input with stored memory
P200
P300
LITERATURE
EEG STUDIES ON OBESITY IN THE
food cue
incr. neural activity
food-abundant
"heightened responsiveness"
to overeating
environment
interference with higher "executive" mental function
INDICATOR: EEG ERP LATENCY & AMPLITUDE
INDICATOR: PERFORMANCE ON COGNITIVE TASK
RAN CONCURRENT WITH EEG TEST
CORRELATION WITH HABITUAL EATING BEHAVIOURS E.G. DISINHIBITED EATING PRACTICES
a few basic descriptive stats:
Cosmed CPET metabolic data check!
promising EEG data ...
SUBJECT RECRUITMENT:
REDUCED SUBJECTS: n = 14
LEAN CONTROLS: n = 18
RELAPSED SUBJECTS: n = 4
OBESE CONTROLS: n = 8
N = 44
ENTIRE PROTOCOL:
LEAN CONTROLS: n = 45
OWt SUBJECTS: n = 12
OBESE SUBJECTS: n = 20
OWt/Obese: n = 32
N = 77
EEG SUB-STUDY:
<10%
Garner DM, Garfinkel PE. (1980), Garner DM, Olmsted MP (1984), Klesges RC, Meyers AW, Klesges LM, La Vasque ME. (1988), Leibel RL, Rosenbaum M, Hirsch J. (1995), Ross R. (2009)
RELATIONSHIP BETWEEN % WEIGHT REDUCTION
AND % SUCCESSFUL WEIGHT LOSS MAINTAINERS
Kraschnewski et al. Int J Obes [2010]
King et al. Metabolic and Behavioral Compensatory Responses to Exercise Interventions: Barriers to Weight Loss, OBESITY Vol. 15 No. 6 June 2007
"Evolutionary-based protective mechanisms to prevent starvation and an indefinite decr. in body weight "
HYPERPHAGIA
[Smith & Minson 2012]
[SB Heymsfield et al. Am J Cl Nutr 2007]
Increased potential for GNG in food-scarce scenarios
[due to decreased perfusion distance from vital organs]
EXCITATORY VS INHIBITORY
BRAIN ACTIVITY IN RESPONSE
TO FOOD CUES
PRESENT IN THE
ENVIRONMENT
44 MTG +
33 "EEG only" subjects
WHY? 2 separate questions being asked:
How does the processing of food-related stimuli relate to:
Disinhibited eating practices
Awareness of body shape
Perception of body image
Cognition and attention
along the BMI continuum irrespective of weight hx?
What is the relative contribution of each of the compensatory response categories i.e.
Physiological
Behavioural
Perceptual
that render individuals as either resistant or susceptible to weight regain?
ERPs SOURCED FROM THE
LEFT PARIETAL LOBE (P3)
The tip of
the iceberg...
NARROWING IT DOWN: DEFINING THE SCOPE OF
THE DISSERTATION
Logical delegation of testing as per variables under investigation ...
The natural focus area:
Perceptual variables
to explore:
A final word:
Motivation for
Degree Upgrade:
E.G. avg of 15 randomly generated "triggers"
[Ob]: Linear, unipolar response indicates:
Absence of a "checking system"
Direct engagement with food stimuli
HO: will be confirmed by latency in RT on Stroop Task
because of "interference/distraction" caused by food cues
What this may indicate:
P300 = motivation and drive
"Executive dysfunction"
Can be compared to addiction responses
Same neural pathways?
[NW & OW]: Multipolar response:
Evaluation and REGULATION
Trial 1:
Anthro, OGTT, TM test, GT3X -

DJ

Trial 2:

The High Fat Meal -
Louise Clamp

Trial 3:
The EEG -
DJ
What is the relative contribution of each of the compensatory response categories i.e.
Physiological
Behavioural
Perceptual - past research on level of agreement between objective vs subjective PA behaviours
that render individuals as either resistant or susceptible to weight regain?
interim: questionnaire and online dietary data
perception
reality
GAP
high
risk
low
risk
PA
[EG: PHYSICAL ACTIVITY]
1) OBJECTIVE VS SUBJECTIVE MEASURES IN 3 DOMAINS:
PA DOMAIN:
Weekly habitual PA [GT3X]
Exercise intensity [RPE vs HR response]
NUTRITIONAL DOMAIN
Food portion sizes
Satiety [VAS vs Hunger Hormone response]
BODY SHAPE AWARENESS DOMAIN
Body type [Body Image Discrepancy Score]

2) PERCEPTION OF VISUAL FOOD CUES
MTG groups
Along BMI and Body Comp continuums
MSc Level
PhD Level
METHODOLOGY
METACOGNITION
NOVEL EEG COMPONENT
IN SA CONTEXT
The experimental procedures have evolved into an avenue that offers exploration of the sparsely researched but highly relevant issue of
WEIGHT LOSS RELAPSE

It offers the level of thoroughness necessary to identify the relative contribution of the various physiological, behavioural and perceptual factors which are implicated, and may be related to the increasing global prevalence of obesity
THANK YOU
Hyperinsulinemia + central hypothalamic insulin receptors (not reliant on facilitated uptake by transporters) = Sympathetic NS overdrive
Hypothalamus contains satiety centre (feeding responses)
Lypo- Gluco- & Amino-static implications (adrenal glands & pancreas)
Endothelial dysfunction
SAMPLING AREA
SAMPLING AREA
FREQUENCY ANALYSIS: AROUSAL OF DEEPER ANATOMY
SCALP
SKULL
CYLINDER SURFACE
PYRAMIDAL CELL
PHYSIOLOGY
Presented by: DJ Hume

Primary Academic Supervisor: Prof. EV Lambert

Co-supervisors: Dr. Fleur Howells, Dr. Laurie Rauch, Dr. Jacolene Kroff
"EVERY PROPER LADY SHOULD CURTSEY"
Master's Level
P
Doctoral Level
1) Initial protocol: Energy and substrate metabolism, eating and exercise behaviours, body concern

2) EEG: Methodological Chapter of MSc with lower level of analysis

3) Visit 2: Fasting bloods only

4) Dietary analysis via FFQ & logbooks
1) Revised protocol: Holistic and TRANSPARENT allowing for a greater level of sensitivity of measures

2) EEG: Evolved into powered sub-study with more in-depth ERP and frequency analyses (arousal)

3) Visit 2: Repeated blood measures

4) Dietary analysis via ASA24 (more innovative)

5) Rigorous screening (e.g. OGTT) & steady recruitment

7) NB: Prelim data warrents FUTURE RESEARCH (eg fMRI)
Project Evolution
LOUISE CLAMP
PAULA PIENAAR
Full transcript