Body Weight and Satiation After Duodenal Switch 2 Years Later

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Springer Science + Business Media, Inc. Obesity Surgery, 17, 2007 631

Obesity Surgery, 17, 631-636

Background: The authors investigated body weight,

satiation, and gustative pleasure of obese patients 2years after a bariatric operation: the biliopancreatic

diversion with duodenal switch (DS).

Methods: 9 operated patients, 10 unoperated non-

obese and 10 unoperated obese persons participated

in the alliesthesia (food distaste) test.This test is a

psychometric assessment of satiation resulting from

the pleasure or displeasure following the repeated

ingestion of a sweet stimulus. Operated patients also

participated in the test before the DS operation.

Results: 2 years after DS, patients had lost 50% of

their body weight and their BMI was rendered similar

to that of the non-obese control group.Their satiation

was faster than in control and unoperated obesepatients. The responses of control and unoperated

obese patients were identical to those of pre-surgery

operated patients.

Conclusion: This indicates that at the time of the

experiment, patients actual body weight was higher

than their body weight set-point and that they would be

likely to continue to lose weight, at least beyond 2 years.

Key words: Morbid obesity, bariatric surgery, duodenal

switch, alliesthesia, taste, set-point

Introduction

Bariatric surgery has become increasingly popular

to cure morbid obesity. It is now widely accepted

that such surgery is the most effective treatment to

lose weight and improve obesity-related health

problems.1,2 Over 10,000 biliopancreatic diversionswith duodenal switch (DS) have been performed

over the last 15 years, and the popularity of this sur-

gery is still growing.3 This surgery4-6 combines

restrictive and malabsorptive effects and, after 2 to

10 years according to reports, removes about 75%

of excess weight.1,5,7,8

In a previous paper, Marceau et al9 reported that

satiation was accelerated in patients 3 and 6 months

after duodenal switch, while they lost weight and

moved from a mean BMI of 56.7 to 40.3 kg/m2. In

the alliesthesia test, developed by one of us,10-12patients ingest repeatedly a sweet stimulus and they

report quantitatively the pleasure that they felt after.

This test assesses initial pleasantness of the stimu-

lus, satiation time course, and negative alliesthesia,

i.e. the time it takes for a stimulus to pass from

pleasantness to unpleasantness. Marceau et al9 inter-

preted the accelerated satiation and alliesthesia that

they observed in their patients as resulting from a

lowered body weight set-point that explained the

patients rapid weight loss.

Based on experimental data, it has been proposedthat body weight is regulated at a set-point.10,13-19 In

a regulated system, any long-term change of the reg-

ulated variable mustbe mediated by a change in set-

point. In the case of body weight, any method to lose

weight must lower the body weight set-point if

weight loss is to be maintained over a long-term.

Otherwise, negative feedback would come into play

and counter any drop in body weight, and in this

case, the body weight would eventually return to its

Body Weight and Satiation after Duodenal Switch:

2 Years Later

Sebastien Paradis, PhD1; Michel Cabanac, MC1; Picard Marceau, MD,

PhD2; Patrick Frankham, PhD1

1Centre de recherche sur le mtabolisme nergtique (CREME), Anatomy and Physiology

Department, Laval University, Qubec, Canada; 2Centre de recherche de lHpital Laval (CRHL),

Chirurgie gnrale, Laval Hospital, Qubec, Canada

Correspondence to: Michel Cabanac, Anatomy and PhysiologyDepartment, Laval University, Qubec G1K 7P4, Canada. Fax:418-656-7898; e-mail: [email protected]


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initial value. Thus, what should be explored in the

long-term is the influence of surgery on the set-point.

Clinical data show that there is an important and

continuous body weight loss during the first 2 years

after surgery, then a slight body weight regain of a

few kilograms, and eventually a more or less stableweight. Since the 2-years cap seems to present an

important shift in body weight change, we investi-

gated those patients presented previously9 and stud-

ied their body weight, satiation, and negative allies-

thesia at this particular interval after their operation.

Methods

Study Participants

Nine patients already studied, before, 3 and 6

months after biliopancreatic diversion with duode-

nal switch (DS) were studied again at 2 years after

surgery. Their mean BMI at the time of surgery was

56.7 4.2 kg/m2. Two years later, mean BMI was

28.4 1.4 kg/m2 with major improvement in their

general health status and healing of most co-mor-

bidities like sleep apnea and diabetes.

Ten non-obese, non-diabetic individuals were

recruited as control group. Smokers were excluded

because it had been shown that transient nicotine

can lower the set-point for body weight in humans,20

and in rats.21 The non-obese control group had a

mean BMI of 25.7 1.4 kg/m2.

Alliesthesia Test

Participants were instructed to arrive at the hospital

laboratory early in the morning, having fasted

overnight (e.g. skipped morning meal). All sessions

were conducted between 8:00 and 10:00 h.

Participants were tested individually under strict

confidentiality conditions. Body weight was record-ed before initiating the experimental session.

A sweet stimulus (common commercial caramel

candy: 6 g, 105 kJ total / 16.7 kJ from fat) was given

every 3 minutes to the participant. Fifteen seconds

after a stimulus was mouthed, the participant had to

indicate the pleasure experienced. This was done by

writing a mark on an analog 300-mm line. One end

of the line rated pleasantness, and the other end,

unpleasantness. The middle of the line rated indiffer-

ence. There was no numerical grading on the chart

except a middle mark for 0 (indifference). After

the patient wrote a mark on the scale, the distance

from zero was measured in millimeters and the mark

was removed by the experimenter after measure-

ment, in order to avoid influencing the next rating.Before the test, participants were instructed that they

could stop the test whenever they wanted to.

Measurements and Statistics

The BMI (kg/m2) of each participant was calculated.

The alliesthesia test measured pleasantness or

unpleasantness on a basis of 150 mm (e.g. each side

of 0). For each participant, we obtained three criti-

cal pieces of information: 1) initial rating was the

score given after the first stimulus; 2) time before neg-

ative rating was the time taken for the stimulus to pass

from pleasant to unpleasant, i.e. for the participants

rating to reach zero; and 3) satiation was the time at

which the participant wanted to stop the test.

Intergroup differences were compared by analyses of

variance (ANOVA) for repeated measures; paired post

hoc Students t-test was performed when necessary.

To compare dynamics of satiation of different groups,

we used the Kaplan-Meyer method for survival rate.

Ethics

The study protocol was approved by Laval

University Ethics Committee and Laval Hospital

Independent Ethics Committees (2001-141 A-1 R-

2). Each subject signed an informed consent before

study initiation. All sessions were conducted under

strict confidentiality conditions. Patients received

twenty dollars per visit as a compensation for their

participation in the study.

Results

BMI. The BMI (kg/m2) of operated patients contin-

ued to decrease 2 years after the DS operation, thus

confirming the results recorded 3 and 6 months after

surgery (Figure 1). After surgery, BMI fell from

56.7 4.2 to 46.5 4.0 (P


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patients had lost 50% of their body weight and their

BMI was rendered similar to that of the non-obesecontrol group, whereas weight remained stable over

the 6 months for the control obese group with a con-

stant BMI around 46 for the whole period (0, 3, and

6 months after surgery). Operated patients all

reported a better subjective quality of life and

expressed that they were satisfied with the results of

the surgery. They all reported that they were contin-

uing to lose weight without any significant effort.

Initial Rating. Operated patients gave a mean ini-

tial rating (pleasantness rating after the first stimu-lus) of 46.1 23.3 mm, compared to 78.8 15.7

mm before surgery, and 86.2 15.9 in non-obese

controls. This finding was not significantly lower 2

years after the surgery than before the surgery or

than in controls (Figure 2A; P=0.17).

Time before Negative Rating. Mean time before

negative rating 2 years after surgery was 8.1 1.4

min, which is lower than before surgery (16.0 3.9

min) or than in non-obese controls (24.9 5.5 min).

Thus, negative rating continued to appear faster in

operated patients 2 years after DS than in controls or

before the DS (Figure 2B; P=0.018).

Satiation. Two years after surgery, satiation timewas 12.7 2.2 min in operated patients, 26.7 5.0

min before surgery, and to 31.0 6.0 min in non-

obese controls. Therefore, satiation also continued

to appear faster in operated patients 2 years after the

surgery than in controls or before the surgery (figure

2C; P=0.014).

Two years after surgery, abandon rate was faster in

the group of operated patients than initially and in con-

trols (Figure 3). Thus, the results were identical as at 3

and 6 months after surgery. The longest session among

operated patients was 24 min, but was 84 min for the

non-obese controls and 81 min for obese controls.

In operated patients, the three measures of initial

rating, time before negative rating, and satiation

were similar to those obtained 3 and 6 months after

surgery. Non-obese and obese controls results were

similar to those of patients before the surgery for all

these three measures.

Discussion

Two years after surgery, the nine patients followed

in this present work had lost half of their weight.

That reaffirmed the efficacy of BPD-DS to reduce

body weight. Also, all patients considered that they

had made a good decision when they had applied for

surgery and they all declared that if they were in

their previous morbid state, they would make the

same decision again without hesitation.

Two years after surgery, patients negative rating

and satiation were still accelerated and all patients

reported that they were continuing to lose weightwithout special effort. This indicates that their actu-

al body weight remained somewhat higher than

their body weight set-point. If so, they are likely to

further lose weight. However, a non-significant

increase in the three measures related to taste and

satiation (initial rating, time before negative rating,

satiation time) further away from their surgery, with

decreasing body weight, might indicate a trend to a

return toward initial values similar to those of unop-

Satiation 2 Years after Duodenal Switch

Obesity Surgery, 17, 2007 633

0

10

20

30

40

50

60

70

Operated Obese controls Non-obesecontrols

Before surgery3 months after6 months after2 years after

a b c d

b b b

Figure 1. BMI of patients with a duodenal switch (n=9),

obese controls (n=10) and healthy controls (n=10). Two

years after the duodenal switch, the BMI of patients with

duodenal switch was half of the BMI before the surgery

and became similar to the BMI of healthy controls. Obese

controls without surgery maintained their high BMI.

Columns with different lowercase letters indicates signifi-

cant differences (P


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Paradis et al

634 Obesity Surgery, 17, 2007

0

20

40

60

80

100

120 Before surgery

3 months after

6 months after

2 years after

InitialRating

(mm)

A

0

5

10

15

20

25

30

35

* * *TimebeforeNegat

iveRating

B

0

5

10

15

20

25

30

35

40

Operated Obese controls Non-obese controls

* * *Satiation(min)

C

Group

Figure 2. (A) Initial rating, (B) negative alliesthesia, and (C) satiation of patients with a duodenal switch (n=9), obese con-

trols (n=10) and healthy controls (n=10). Two years after the surgery, results of DS patients remained similar to results at 3

and 6 months after the DS. Healthy controls results were also similar to those of obese controls. Columns with * indicatesignificant differences (P


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erated patients and control subjects. This may mean

that operated patients body weight was about to

match their set-point and that their body weight

would soon stabilize. This interpretation is consis-

tent with the long-term time-course after DS:

patients kept losing weight during the first 2 yearsafter surgery. Later, they tended to regain some of

the weight lost, and then they maintained a more or

less stable body weight.1,5

Obesity and body weight are the result of energy

balance, food intake, and energy expenditure. Food

intake is the result of experience of hunger, satiety,

and pleasure. It follows that these psychobiological

signals obey the regulatory set-point. The concept of

set-point does not prejudge the underlying cause of

obesity. The initial mechanism may be nervous or

endocrine. The fact that satiety and alliesthesia were

modified by surgery does not mean that resulting

weight loss is caused only by modulation of appetite

and satiation, nor that morbid obesity is caused by

excessive eating. Indeed, the causality may be

inverse. Morbid obesity is a complex disease that

excess food intake alone fails to explain.22 We used

these behavioral parameters (satiation, alliesthesia)

in order to investigate the patients regulatory func-

tion. A lowered set-point might also affect non-

behavioral mechanisms as well, such as an adjust-

ment of metabolism. Yet, modification of alliesthesia

is a measurable observation indicating a deep physi-ological change in whole body weight regulation.

Altogether, these results may contribute to the

debate about the causes of obesity. They tend to

show that morbid obesity is associated with a raised

body weight set-point but that the regulatory

processes are still working accurately at the new set-

point. Patients and obese controls alliesthesia

responses were normal and similar to those of non-

obese controls. Such a result also supports the con-

cept that the efficacy of a weight-loss method would

depend on the way that this method affects the set-point. The fact that BPD-DS lowers the set-point

may explain the long-term efficacy of this method.

When compared to the patients huge weight loss

and psychological comfort, these results show that a

set-point change is the best, and possibly only, way

to reduce body weight in the long term, whereas

dieting alone invariably leads to relapse.

It is of interest to note the consistency of results

obtained with the alliesthesia test. Results in operated

patients remained similar through the three sessions

over the 2 years after surgery. Furthermore, all allies-

thesia measures (initial rating, time before negative

rating, and satiation) were similar in the three obese

control tests and in non-obese controls. Such consis-

tency and reproducibility would validate the use ofthe alliesthesia test in clinics to explore the patients

ponderal state. The alliesthesia test should be a good

tool to assess the efficiency of different ways to lose

weight, whether the weight loss is achieved with sur-

gical, pharmacological,20 or dietary methods.

This work was supported by a grant from Natural Sciences

Engineering Research Council of Canada (NSERC). We thank

Suzy Laroche and Zo Lebel-Castonguay for their assistance in

study coordination.

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Body Weight and Satiation After Duodenal Switch 2 Years Later