Transcript BFDG-FCC April 2006 Symposium Individual differences in eating behaviour: can they explain variation in adiposity? Getting evidence for most and least fattening local eating customs from.

BFDG-FCC April 2006
Symposium
Individual differences in eating behaviour:
can they explain variation in adiposity?
Getting evidence for
most and least fattening local eating customs
from individuals’ reports
in their culture’s terms
David Booth, Psychology, U Bham, England
Louise Thibault, Nutrition, McGill U, Quebec
Caroline Chesneau, INA, Paris, France
Seolhyang Baek, Nursing, Dongguk U, S Korea
Theory
1. A subculture’s consensus descriptions of customs
objectify communicable patterns of activity.
2. Autobiographical memory can time episodes of
an activity as accurately as a diary record can.
3. A sustained change in frequency of a custom of
eating or moving about will change body weight
towards asymptote over a few weeks.
4. Change to a frequency that is sufficiently prevalent
in a culture will be maintained indefinitely, along
with the asymptotic change in body fat content.
Method (with some short-cuts for this pilot study)
1. Consensus descriptions elicited in one culture (UK)
were ‘localised’ to another culture (Quebec French)
by investigators as participant observers, checked by
back-translation to England’s language and environs.
2. Exact current frequency is given by the reciprocal of
the time difference between the last two occasions.
3. Effect on weight of maintained change in frequency
of a custom after the first week (or 2 weeks) was
measured by correlation between the changes,
4. Effects of initial and changed custom frequencies on
behaviour change maintenance (and weight change
maintenance for an effective custom) were expressed
as ‘dose- response’ slopes.
Design
Convenience sample of French-speakers in Montreal:
21 recruited; 14 completed the planned 6 weeks of the
study: 12 women and 2 men, ages 18-46 years.
At the same time of day on the same day of the week, on
a questionnaire in French, each reported body weight
(weighed that day on the same scales) and recalled the
last two timings of carrying out each of 26 customs of
eating and/or drinking and 6 customs of moving about.
Correlations of changes in behaviour and weight
Results are expressed here as r x 100, where r is
Pearson’s product-moment correlation coefficient.
[Where data are seriously skewed, Spearman’s correlation of
ranks, rho, should be used instead.]
If only one pattern of energy intake or expenditure
changes in frequency in a given week, correlation
with weight change can in theory be perfect (r = 1.0).
With such a small sample, the observed r values are
highly unreliable. [When N is adequate for good estimates
of effect size, the 95% confidence limits of r should be given.]
Correlations of changes in behaviour and weight
Positive values indicate that the activity is fattening.
Negative values indicate an effective slimming habit.
Test of the causal hypothesis:
Frequency change correlates with later Weight change.
This is a rather severe test, discounting weight lost in 1st week or two (though 1st week is mainly water).
Cross-lagged control:
Weight change does not correlate in the same direction
with later Frequency change.
Correct the r-value measuring Frequency on Weight by subtracting r-value for Weight on Frequency.
Effect of belief on behaviour:
Weight change correlated in the opposite direction with
later Frequency change indicates action on a correct
belief as to what can produce that change in weight.
Evidence for eating that slims in Francophone Canada
correlation of amount of one change in first week of that change
with amount of the other change in subsequent two weeks
r x 100
Freq 0-1
Wt 1-3
Activity (described
in French = “…”)
r x 100
rF,W - rW,F
rW,F/rF,W
Wt 0-1 Cross-lag Strength
Freq 1-3 corrected of belief
smaller meal a
-63
-50
-13
-
vegetables in meal
-85
54
(-85)
0.6
cheese, dairy cream b
-93
38
(-93)
0.4
food with added sugar
-25
58
(-25)
2.3
“sucreries en ‘surplus’”
-30
45
(-30)
1.5
a
smaller than ‘normal’.
b
“des matières grasses animales [sic] sous forme de ...”
Customs that slim in Montreal (described in French)
Means of correlation values (r x 100) available from up to four lags:
behaviour-Frequency change over one week (F0-1) or two weeks (F0-2)
and Weight change over the next week (W1-2,W2-3) or two (W1-3,W2-4).
Mean
Freq
on Wt
Mean
Wt on
Freq
Mean
cross-lag
corrected
Mean
strength
of belief
smaller meal
-62
-43
[-60]
0.9
vegetables in meal
-28
-9
-14
[3.0]
cheese, dairy cream
-70
17
-48
0.2
food with added sugar
-6
45
[-6]
4.3
“sucreries en ‘surplus’”
-10
16
1
-
take exercise until tired
-34
-28
[-15]
2.4
Pattern of behaviour
[…] = (mean) difference from two of the four (or one of the three) lags available
Customs that fatten in Montreal (described in French)
Frequency change over one week (F0-1) or two weeks (F0-2) and Weight
change over the next week (W1-2,W2-3) or two (W1-3,W2-4) - mean values
Mean
Freq
on Wt
Mean
Wt on
Freq
Mean
cross-lag
corrected
Mean
strength
of belief
use fat in cooking/prep’n
59
20
57
-
drink alcohol
53
-48
(40)
1.1
choose fibre-rich foods
55
11
31
-
eat fruit or salad
73
7
65
-
aerobics/“un club sportiv”
75
18
62
-
Pattern of behaviour
Other ways to test the causal hypothesis
e.g., correlation (unlagged) of a persisting change in
frequency of an activity with the amount of weight lost
Less food than normal in a meal
10.00
12
0.00
Biggest change in Frequency
Each
person’s
biggest
change in
frequency
during a
period of
consistently
up or down
change
Increase in frequency with
greatest decrease in weight
2
1
13
7
-10.00
-20.00
-30.00
14 6
Decrease in frequency
(briefly) with (almost) no
change in body weight
R Sq Linear = 0.396
-40.00
0.00
1.00
2.00
3.00
4.00
5.00
weight change
Change in weight (kg t1 – t2)) over whole period of change
Does maintenance of changed frequency of a practice
depend on how frequent the custom was or is?
Less food than normal in a meal
o
f
6
6
N
u
m
b
e
r
2
12
No.of week
No.of week
N 5.00
u
m
b 4.50
e
r 4.00
3.50
o
f
1
4.50
2
12
4.00
3.50
down
7
7
up
1
3.00
3.00
w
e
e
k
s
5.00
w
e
e
k
s
2.50
13
2.00
0.00
3.00
6.00
9.00
12.00
F0
Starting frequency (times per week)
Change in frequency [increase*] of
eating smaller meals is maintained
for longer if frequency starts higher.
2.50
R Sq Linear = 0.311
R Sq Linear = 0.386
13
2.00
15.00
-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
F0-1
Frequency change in first week of change
No sign of effect of size of increase* in frequency.
(Sharp decreases were not well sustained.)
Implications
The psychobiological “long haul”:
= study of the mechanisms of appetite and its sating,
and of vigour and its fatigue
.
physically energetic
- by itself, such work can’t show how to control weight;
- yet the mechanisms of choice and its satiety/fatigue
must be measured, in order to work out how to
support these psychosocially identified
maintainable least fattening customs,
e.g. through supply of foods, transport, leisure, etc.
Implications
Meanwhile:
Personally tailor locally valid evidence
to inform a succession of changes each 1-3 weeks,
- especially of eating habits when
a more sedentary lifestyle begins.
Track changes in behaviour components
- the only way to rescue obesity RCTs
from unusability and invalidity.
END